In the evolutionary mating game, brawn and stealth rule, scientists find

ScienceDaily (Dec. 27, 2010) — When prowling for a hook up, it's not always the good-looker who gets the girl. In fact, in a certain species of South American fish, brawn and stealth beat out colorful and refined almost every time.

In a series of published studies of a South American species of fish (Poecilia parae), which are closely related to guppies, Syracuse University scientists have discovered how the interplay between male mating strategies and predator behavior has helped preserve the population's distinctive color diversity over the course of time. The third study in the series was published Dec. 23 in BMC Evolutionary Biology, a publication of BioMed Central, London. The studies were supported in part by grants from the National Science Foundation (NSF).

"Poecilia parae are an ideal model for investigating how genetic diversity originates and is maintained within a species," says study author Jorge Luis Hurtado-Gonzales, a Ph.D. candidate in the Department of Biology in SU's College of Arts and Sciences. "The findings may help us better understand how to protect biodiversity in larger ecosystems." Hurtado-Gonzales' co-author is J. Albert C. Uy of the University of Miami.

Like guppies, Poecilia parae sexually reproduce and their offspring are born live. Unlike guppies, in which no two males have exactly the same color patterns, Poecilia parae males come in five, genetically determined colors -- red, yellow, blue, parae (clear with a black stripe), and immaculata (drab gray that mimics the color of immature females). When found in the wild, the abundance of each color group represented in the total population is relatively constant despite the fact that females prefer to mate with the more striking reds and yellows.

"If females prefer red and yellow males, then one would think that red and yellow would dominate and the other colors would phase out over time," Hurtado-Gonzales says. "However, red and yellow are the rarest colors found in the wild."

The most recent study in BMC Evolutionary Biology found that while females prefer reds and yellows they go for the winner of fin-to-fin combat in a significant number of cases. In the study, the larger parae almost always prevailed, thus gaining a mating advantage despite its less-than-desirable coloration. Immaculatas, which are the smallest males, generally shunned the showy displays of violence and were mostly ignored by all but yellow males. The larger yellows almost always defeated immaculatas, stopping them from approaching females.

"In the absence of male-to-male competition, we found that females will almost always choose a red male," Hurtado-Gonzales says. "However, if the red loses a fight, the female will generally seek out the winner. In most cases, that is the larger parae, which is the most dominant male."

Immaculatas compensate for their lack of physical prowess and attractiveness through a mating strategy that relies on stealth. In a 2009 study published in the journal Animal Behavior, Hurtado-Gonzales found that the immaculatas' drab color provides camouflage that enables them to stealthy mate with females while the more colorful red males were wooing them. Females are promiscuous and will mate with multiple males. Additionally, immaculatas have developed larger testes, which produce more sperm, providing a post-mating advantage in the race to fertilize female eggs.

Finally, in a study published earlier this year in the Journal of Evolutionary Biology, produced by the European Society for Evolutionary Biology, Hurtado-Gonzales found that a common predator of Poecilia parae prefers to dine on reds and yellows, most likely because their striking colors make them easier to see. This predatory disadvantage contributes to the lower numbers of reds and yellows in the overall population.

"It seems that within an evolutionary scale, the less attractive males persist in the population over their more attractive counterparts by evolving unique, but likely equally effective mating strategies," Hurtado-Gonzales says. "Therefore, the maintenance of multiple colors may result from the interaction between predator control of attractive males (reds and yellows) and the ability of less attractive males to exploit other areas of sexual selection, including male dominance, sneak behavior, and sperm competition."

A forthcoming study will focus on how blue males gain a mating advantage. Early results indicate that blues exploit habitats in which blue light waves maximize their attractiveness to females and possibly limit their vulnerability to predators.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Syracuse University, via EurekAlert!, a service of AAAS.

Journal Reference:

Jorge L. Hurtado-Gonzales, J. Albert C. Uy. Intrasexual competition facilitates the evolution of alternative mating strategies in a colour polymorphic fish. BMC Evolutionary Biology, 2010; 10: 391 DOI: 10.1186/1471-2148-10-391

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Recycling and depolluting the phosphorus in livestock waste

ScienceDaily (Dec. 6, 2010) — Phosphorus is an ingredient in agricultural and household products such as fertiliser, detergents, etc. When released in excessive quantities to the environment, this mineral contributes to the development of algae and micro-organisms that pollute water, thus impacting on fishing, fish farms, swimming areas and drinking water. At Cemagref, scientists are developing a means to recycle the phosphorus present in animal effluents and limit water pollution. The new process may represent a solution for the future, given the depletion of natural phosphorus and the resulting increase in farm operating costs.

A product of mined phosphate rock  phosphorus is an indispensable element for life. In agriculture, it is used in mineral form to boost the growth of crops and animals. However, if it is incorrectly assimilated or used in excess, large quantities are subsequently released to the environment through erosion and run-off. In areas with intensive crop farming and/or animal production, over 50% of the phosphorus in rivers is the result of such diffuse pollution. A further source is the phosphorus used in detergents that is released in household wastewater. The excessive quantities of this mineral cause eutrophication in rivers and the development of certain bacteria that impact on water quality, thus affecting fishing, fish farms, swimming areas and drinking water.

Recycling in addition to good agricultural practices

To limit these risks, the regulations on spreading of phosphorus-based products now encourage farmers to reduce quantities of fertiliser. But in intensive animal-production zones such as Brittany, the quantities of phosphorus (and nitrogen) produced via animal effluents and available as fertiliser exceed the amounts needed for crops. How can the manure be treated to recover the phosphorus so as to be transportable to other regions, thus limiting pollution levels?

At Cemagref, scientists are developing processes to recycle phosphorus, whether from wastewater-treatment plants or agricultural effluents, so that it can then be used as a direct substitute for phosphate-based mineral fertilisers. A team is paying particular attention to the various types of phosphorus contained in livestock effluents and how they are modified during treatment. Between 60 and 80% of the phosphorus is in the form of mineral particles that settle with the organic matter.

A four-step process

The team has designed a process to separate the phosphorus from the organic matter in the effluents. It comprises four steps, i.e.

1) dissolve the phosphorus using formic acid, thus making it recoverable in the liquid phase,

2) separate the solids from the solution containing the phosphorus,

3) precipitate the solution chemically by adding magnesia to crystallise the phosphorus, and

4) filter the solution to recover the phosphorus in mineral form for use as a fertiliser. The goal is to obtain large crystals which are easier to filter and dry. Process optimisation depends on improving the separation step, prior to precipitation. If the solids are simply decanted, only 50% of the phosphorus can be recycled, but the crystals are large enough to be filtered. Another technique involves adding a polymer and then straining the solution before precipitation, which results in 80% recovery of the phosphorus, but the crystals are small and difficult to filter. The researchers are continuing their efforts to optimise this essential crystallisation step in order to devise the best conditions to produce large crystals and improve recycling efficiency).

Take action prior to the depletion of natural phosphate supplies

On the basis of current knowledge, phosphorus recycling necessarily includes the acid-dissolution step, whose high cost constitutes the main economic obstacle to wider use of this recycling process. The work carried out at Cemagref on these economic aspects, in conjunction with the European university of Brittany, has revealed that recycled fertiliser is not competitive with imported, chemical fertilisers. However, that should change over the coming decades due to the increase in fertiliser prices caused by the progressive depletion of phosphate reserves and the resulting increase in extraction costs. Though estimations diverge on when phosphorus supplies will be depleted, currently exploitable reserves may be gone within the next century.

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Pterygotid sea scorpions: No terror of the ancient seas?

ScienceDaily (Dec. 24, 2010) — Experiments by a team of researchers in New York and New Jersey have generated evidence that questions the common belief that the pterygotid eurypterids ("sea scorpions") were high-level predators in the Paleozoic oceans. This group, which ranged the seas from about 470 to 370 million years ago (long before the dinosaurs appeared), included the largest and, arguably, scariest-looking arthropods known to have evolved on planet Earth.

Reaching lengths of 2 ½ meters with a body supported by well-developed legs, and armed with a pair of forward-facing claws laden with sharp projecting spines, they seem like the Tyrannosaurus rex among the invertebrates.

But in a new study, published in volume 39 of the Bulletin of the Buffalo Society of Natural Sciences, Richard Laub (Buffalo Museum of Science) and his colleagues Victor Tollerton (Research Associate, New York State Museum) and Richard Berkof (Stevens Institute of Technology) show that the mechanical constraints on the claw of the pterygotid sea scorpion Acutiramus made it incapable of penetrating the external shell of a medium-sized horseshoe crab without danger of rupturing.

They suggest that these imposing sea scorpions, and by extension others of their family who lived in the seas about 470 to 370 million years ago, were not necessarily the voracious predators they are commonly believed to have been. The practical operational force that could be safely applied by the claw of Acutiramus without causing damage to it was no more than about 5 Newtons, whereas a force of 8-17 Newtons was required to penetrate the horseshoe crab's armor.

Laub's team also noted that the absence of an 'elbow joint' between the claws and the body of Acutiramus limited claw movement, making them more effective in grasping prey on the sea floor than capturing actively fleeing fish or other swimming animals. Armed with serrated spines, the claws may have been used together to both capture and shred the prey, but the predatory capabilities of Acutiramus would appear to lack the force necessary for this animal to operate as a major predator.

"I have long been suspicious of prevailing popular interpretations" said Dr. Roy Plotnick, Department of Earth and Environmental Sciences at the University of Illinois at Chicago, who was not involved in the study. "This is a welcome contribution that strongly supports an alternative interpretation of claw function" he said.

"Our results derail the image of these imposing-looking animals, the largest arthropods yet known to have existed, as fearsome predators, or at least as predators of other eurypterids and of the armored fishes of the time" said team leader Richard Laub, who noted that "it opens the possibility that they were scavengers or even vegetarians."

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Journal Reference:

Laub, R.S., Tollerton, Jr. V.P. and Berkof, R.S. The cheliceral claw of Acutiramus (Arthropoda: Eurypterida): Functional analysis based on morphology and engineering principles. Bulletin of the Buffalo Society of Natural Sciences, 2010; 39: 29

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New evidence for eye-protective effects of omega-3-rich fish, shellfish

ScienceDaily (Dec. 1, 2010) — Researchers at Wilmer Eye Institute, Johns Hopkins School of Medicine, wanted to know how the risk of age-related macular degeneration (AMD) would be affected in a population of older people who regularly ate fish and seafood, since some varieties are good sources of omega-3 fatty acids. A diet rich in omega-3s probably protects against advanced AMD, the leading cause of blindness in whites in the United States, according to the Age-Related Eye Disease Study (AREDS) and other recent studies. High concentrations of omega-3s have been found in the eye's retina, and evidence is mounting that the nutrient may be essential to eye health.

The new research, led by Sheila K. West, PhD, was part of the Salisbury Eye Evaluation (SEE) study.

Food intake information with details on fish and shellfish consumed was collected over one year using a validated questionnaire for 2,391 participants aged 65 to 84 years who lived along Maryland's Eastern Shore. After dietary assessment was complete, participants were evaluated for AMD. Those with no AMD were classified as controls (1,942 persons), 227 had early AMD, 153 had intermediate-stage disease, and 68 had advanced AMD. In the advanced AMD group, the macular area of the retina exhibited either neovascularization (abnormal blood vessel growth and bleeding) or a condition called geographic atrophy. Both conditions can result in blindness or severe vision loss.

"Our study corroborates earlier findings that eating omega-3-rich fish and shellfish may protect against advanced AMD." Dr. West said. "While participants in all groups, including controls, averaged at least one serving of fish or shellfish per week, those who had advanced AMD were significantly less likely to consume high omega-3 fish and seafood," she said.

The study also looked at whether dietary zinc from crab and oyster consumption impacted advanced AMD risk, but no significant relationship was found. Zinc is also considered protective against AMD and is included in an AMD-vitamin/nutrient supplement developed from the AREDS study. Dr. West speculated that her study found no effect because the levels of zinc obtained from seafood/fish were low compared to supplement levels.

A side note: fish and shellfish were part of the normal diet of the study population, rather than added with the intention of improving health. The links between fish consumption, omega-3s and healthy lifestyles were not widely known in the early 1990s when the dietary survey was conducted. In fact, some of the study participants who consumed the most seafood were also smokers and/or overweight, two factors usually associated with AMD and other health risks.

The research is published in the December issue of Ophthalmology, the journal of the American Academy of Ophthalmology.

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Journal Reference:

Bonnielin K. Swenor, Susan Bressler, Laura Caulfield, Sheila K. West. The Impact of Fish and Shellfish Consumption on Age-Related Macular Degeneration. Ophthalmology, 2010; DOI: 10.1016/j.ophtha.2010.03.058

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'No fish left behind' approach leaves Earth with nowhere left to fish, study finds

ScienceDaily (Dec. 3, 2010) — Earth has run out of room to expand fisheries, according to a new study led by University of British Columbia researchers that charts the systematic expansion of industrialized fisheries.

In collaboration with the National Geographic Society and published in the online journal PLoS ONE, the study is the first to measure the spatial expansion of global fisheries. It reveals that fisheries expanded at a rate of one million sq. kilometres per year from the 1950s to the end of the 1970s. The rate of expansion more than tripled in the 1980s and early 1990s -- to roughly the size of Brazil's Amazon rain forest every year.

Between 1950 and 2005, the spatial expansion of fisheries started from the coastal waters off the North Atlantic and Northwest Pacific, reached into the high seas and southward into the Southern Hemisphere at a rate of almost one degree latitude per year. It was accompanied by a nearly five-fold increase in catch, from 19 million tonnes in 1950, to a peak of 90 million tonnes in the late 1980s, and dropping to 87 million tonnes in 2005, according to the study.

"The decline of spatial expansion since the mid-1990s is not a reflection of successful conservation efforts but rather an indication that we've simply run out of room to expand fisheries," says Wilf Swartz, a PhD student at UBC Fisheries Centre and lead author of the study.

Meanwhile, less than 0.1 per cent of the world's oceans are designated as marine reserves that are closed to fishing.

"If people in Japan, Europe, and North America find themselves wondering how the markets are still filled with seafood, it's in part because spatial expansion and trade makes up for overfishing and 'fishing down the food chain' in local waters," says Swartz.

"While many people still view fisheries as a romantic, localized activity pursued by rugged individuals, the reality is that for decades now, numerous fisheries are corporate operations that take a mostly no-fish-left-behind approach to our oceans until there's nowhere left to go," says Daniel Pauly, co-author and principal investigator of the Sea Around Us Project at UBC Fisheries Centre.

The researchers used a newly created measurement for the ecological footprint of fisheries that allows them to determine the combined impact of all marine fisheries and their rate of expansion. Known as SeafoodPrint, it quantifies the amount of "primary production" -- the microscopic organisms and plants at the bottom of the marine food chain -- required to produce any given amount of fish.

"This method allows us to truly gauge the impact of catching all types of fish, from large predators such as bluefin tuna to small fish such as sardines and anchovies," says Pauly. "Because not all fish are created equal and neither is their impact on the sustainability of our ocean."

"The era of great expansion has come to an end, and maintaining the current supply of wild fish sustainably is not possible," says co-author and National Geographic Ocean Fellow Enric Sala. "The sooner we come to grips with it -- similar to how society has recognized the effects of climate change -- the sooner we can stop the downward spiral by creating stricter fisheries regulations and more marine reserves."

The University of British Columbia Fisheries Centre, in the College for Interdisciplinary Studies, undertakes research to restore fisheries, conserve aquatic life and rebuild ecosystems. It promotes multidisciplinary study of aquatic ecosystems and broad-based collaboration with maritime communities, government, NGOs and other partners. The UBC Fisheries Centre is recognized globally for its innovative and enterprising research, with its academics winning many accolades and awards. The Sea Around Us Project is funded in part by the Pew Environment Group. For more information, visit www.fisheries.ubc.ca and www.cfis.ubc.ca.

The National Geographic Society, the Waitt Foundation, the SEAlliance along with strategic government, private, academic and conservation partners including the TEDPrize, Google and IUCN, are beginning an action-oriented marine conservation initiative under the banner of "Mission Blue" that will increase global awareness of the urgent ocean crisis and help to reverse the decline in ocean health by inspiring people to care and act; reducing the impact of fishing; and promoting the creation of marine protected areas. For more information, go to www.iamtheocean.org.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of British Columbia, via EurekAlert!, a service of AAAS.

Journal Reference:

Wilf Swartz, Enric Sala, Sean Tracey, Reg Watson, Daniel Pauly. The Spatial Expansion and Ecological Footprint of Fisheries (1950 to Present). PLoS ONE, 2010; 5 (12): e15143 DOI: 10.1371/journal.pone.0015143

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Link between ancient lizard fossil in Africa and today's Komodo dragon in Indonesia

ScienceDaily (Dec. 30, 2010) — University of Alberta researchers have unearthed a mysterious link between bones of an ancient lizard found in Africa and the biggest, baddest modern-day lizard of them all, the Komodo dragon, half a world away in Indonesia.

Biologists Alison Murray and Rob Holmes say the unique shape of the vertebrae links the 33-million-year-old African lizard fossil with its cousin the Komodo, which has only been around for some 700,000 years.

"The African fossil was found on the surface of a windswept desert," said Holmes. "It's definitely from the lizard genus Varanus and there are more than 50 species alive today, including Komodos and other large lizards."

Holmes says the telltale African vertebrae fossils belonged to a lizard that was about a metre- and-a-half long whose ability to swim may be key to figuring out how more than 30 million years later its ancestors turned up on the other side of the world.

Holmes says the ancient African Varanus specimen was found on land that was once the bottom of a river or small lake. "Whether the animals lived in the water or surrounding land, we don't know, but we do know that some modern day species of Varanus are comfortable swimming in fresh water."

The researchers agree that fresh-water swimming wouldn't get the African lizard all the way to Indonesia. Murray says the mystery of how the animals spread deepens when you consider ancient world geography. "From about 100 million years ago until 12 million years ago, Africa was completely isolated, surrounded by ocean, but somehow they got out of Africa during that period," said Murray. "That's why this paper is important because there was no known land connection."

Murray says one unproven theory of how Varanus moved out of Africa is that over millions of years, small land masses or micro-plates may have moved from one place to another, carrying their fauna with them.

The work of the U of A researchers and various co-authors runs counter to some prevailing theories about the origins of some ancient fossil types found in Africa including Varanus lizards and some fresh-water fish. "The assumption for several types of ancient African fossils is that the animals didn't originate in Africa but came there from Asia," says Holmes. "But the fossil record of Varanus shows exactly the opposite path of migration."

The work of Murray and Holmes and various co-authors was published in the journal Palaeontology.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Alberta, via EurekAlert!, a service of AAAS.

Journal Reference:

Robert B. Holmes, Alison M. Murray, Yousry S. Attia, Elwyn L. Simons, Prithijit Chatrath. Oldest known Varanus (Squamata: Varanidae) from the Upper Eocene and Lower Oligocene of Egypt: support for an African origin of the genus. Palaeontology, 2010; 53 (5): 1099 DOI: 10.1111/j.1475-4983.2010.00994.x

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Pancreas disease transmits horizontally during the seawater phase

ScienceDaily (Dec. 29, 2010) — Researchers and the salmon industry have been debating whether fingerling (young fish) from freshwater farms can be a source of the virus that causes pancreas disease (PD): salmonid alfavirus (SAV). The results of a new doctoral study show that this is not the case: pancreas disease transmits horizontally in the seawater phase and infection in fresh water has little bearing on how the disease spreads.

During her doctoral research, Mona Dverdal Jansen has followed the progression of pancreas disease (PD) in Norwegian farmed salmon from the fresh water phase and throughout the entire seawater phase. The research involved testing 46 different fish populations of farmed salmon from 6 counties for SAV in the fresh water phase, before the fish were released into seawater. SAV was not found to occur in any of these populations.

The 46 salmon populations were transferred to 51 seawater locations, where they were tested for SAV three times during the production phase, including when they were slaughtered. 36 of the 51 locations were situated within the infected zone and 23 (64%) of these 36 were shown to be affected by the SAV virus during the seawater phase. The fish populations were infected during the entire seawater phase, and the risk of infection increased, the longer the fish were in the seawater.

With the exception of three populations, where SAV was detected when the salmon were slaughtered, all the infected populations developed PD. In contrast, no SAV was detected during the production phase amongst the populations released into the 15 uncontaminated seawater locations.

Jansen investigated a number of potential risk factors for infection, but the only factor shown to have any significance was the location within the infected zone. These findings confirm earlier discoveries: that PD infects horizontally from population to population in the seawater phase and that the fresh water phase is insignificant as a source of SAV.

Furthermore, Jansen's thesis describes how, once a population is infected, it remains infected until the time of slaughter. She observed a very varying time lapse between the detection of the SAV virus and the outbreak of PD in some populations. In addition, she found that mortality rates resulting from PD also varied greatly from population to population. She found no signs that the SAV virus was reactivated when the fish were stripped in the one broodstock population she examined.

Dying and thin fish had a higher risk of testing positive in one or more of the diagnostic trials, compared to apparently healthy fish from the same population. This indicates that current routines for taking samples and studying the disease, where dying and clinically abnormal fish are given priority, ought to be continued. The degree of observed conformity between the diagnostic tests employed varied according to which stage of the disease the fish were in.

Jansen carried out genetic analyses of SAV sequences. All belonged to SAV subtype 3 -- the only subtype identified in Norway so far. The sequence variation was found to be somewhat larger than previously reported in the case of one of the genetic fragments studied.

A model based on a stochastic scenario tree indicated that there was an extremely high probability that SAV infection would be absent within the uncontaminated area in the model year of 2007, and this tallied with the results of the field studies.

Jansen carried out her research at the Centre for Epidemiology and Biostatistics at The Norwegian School of Veterinary Science (NVH) and at The National Veterinary Institute from 2006-2010.

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Calculating tidal energy turbines' effects on sediments and fish

ScienceDaily (Dec. 13, 2010) — The emerging tidal-energy industry is spawning another in its shadow: tidal-energy monitoring. Little is known about tidal turbines' environmental effects and environmentalists, regulators and turbine manufacturers all need more data to allow the industry to grow.

Engineers at the University of Washington have developed a set of numerical models, solved by computers, to study how changing water pressure and speed around turbines affects sediment accumulation and fish health. They will present their findings this week at the American Geophysical Union's meeting in San Francisco.

The current numerical models look at windmill-style turbines that operate in fast-moving tidal channels. The turbine blade design creates a low-pressure region on one side of the blade, similar to an airplane wing. A small fish swimming past the turbine will be pulled along with the current and so will avoid hitting the blade, but might experience a sudden change in pressure.

Teymour Javaherchi, a UW mechanical engineering doctoral student, says his model shows these pressure changes would occur in less than 0.2 seconds, which could be too fast for the fish to adapt.

If the pressure change happens too quickly the fish would be unable to control their buoyancy and, like an inexperienced scuba diver, would either sink to the bottom or float to the surface. During this time the fish would become disoriented and risk being caught by predators. In a worst-case scenario, severe pressure changes could cause internal hemorrhaging and death.

It's too early to say whether tidal turbines could harm fish in this way, Javaherchi said. The existing model uses the blade geometry from a wind turbine.

"The competition between the companies is very tight and they are hesitant to share the designs," Javaherchi said.

The researchers are open to working with any company that wants to use the technique to assess a particular turbine design.

Another set of numerical modeling looked at whether changes in speed of water flow could affect the settling of suspended particles in a tidal channel. Slower water speeds behind the turbine would allow more particles to sink to the bottom rather than being carried along by the current.

Javaherchi's modeling work suggests this is the case, especially for mid-sized particles of about a half-centimeter in diameter, about two-tenths of an inch. This would mean that a rocky bottom near a tidal turbine might become sandier, which could affect marine life.

The UW research differs from most renewable energy calculations that seek to maximize the amount of energy generated.

"We are [also] interested in the amount of energy that can be extracted by the turbines, but we are aware that the limiting factor for the development of these technologies is the perception by the public that they might have a big environmental impact," said Alberto Aliseda, a UW assistant professor of mechanical engineering and Javaherchi's thesis adviser.

As to whether any negative effects discovered for tidal turbines would be preventable, Aliseda said, "Absolutely."

"We need to establish what is the lowest pressure that the animals can sustain and the period of time that they need to adjust," Aliseda said. "The blade can be shaped to minimize this effect."

Aliseda says engineers in the wind-turbine industry are already adapting the UW work to look at interactions between wind turbines and bats, since high-frequency pressure changes are now thought to be responsible for the mysterious deaths of bats caused by wind turbines.

"Maybe the best turbine is not the one that extracts the most energy, but the one that extracts a reasonable amount of energy and at the same time minimizes the environmental effects," he said.

The research was funded by a Department of Energy grant to the Northwest National Marine Renewable Energy Center. Joseph Seydel, a Boeing engineer and UW graduate in mechanical engineering, also contributed to the research.

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Restoration activities speed seagrass recovery in the Florida Keys

ScienceDaily (Dec. 16, 2010) — Results of a five-year monitoring effort to repair seagrass damaged in a boat grounding incident suggest that restoration techniques such as replanting seagrass can speed recovery time. The finding is included in a new report released December 16 by NOAA's Office of National Marine Sanctuaries.

The National Marine Sanctuaries Conservation Series report, "N-Control Seagrass Restoration Monitoring Report Monitoring Events 2003-2008," presents results of efforts to repair a nearly 1,000-square-foot (92.8-square-meter) swath of seagrass that was damaged on May 29, 2001, when a 45-foot power boat, the N-Control, grounded in Florida Keys National Marine Sanctuary.

Seagrass beds are an important habitat in the sanctuary. They provide nurseries and homes for numerous species of fish and invertebrates and serve as storm surge buffers for the low-lying Florida Keys. However, shallow seagrass beds in the Florida Keys are being damaged by vessel groundings. In 2007, an estimated 217 reported boat groundings occurred in the sanctuary, with approximately 80 percent occurring on seagrass beds. Vessel groundings damage seagrass, leaving barren areas where marine life once flourished.

Restoration techniques at the N-Control grounding site included replanting seagrass and installing stakes for birds to roost on. The use of stakes to attract birds provides a natural way to fertilize seagrass beds as bird feces are high in nutrients needed by the growing seagrass. Among the key findings in the report:

After five years, the damaged area is gaining seagrass and coral coverage, though it hasn't reached pre-grounding baseline levels.Rather than leaving the site to recover on its own, restoration activities have significantly reduced the amount of time required for damaged seagrass beds in the monitoring area to recover.

"This report highlights the critical science needed to understand and restore our sensitive marine habitats," said Sean Morton, superintendent, Florida Keys National Marine Sanctuary. "It's also an important reminder that boaters need to know where they are going before heading out on the water to prevent groundings in the first place. Make sure you have up-to-date NOAA nautical charts, and always pay attention to the signs, channel markers and informational buoys."

Currently, more than 30 seagrass restoration projects are underway at the sanctuary. Florida Keys National Marine Sanctuary protects 2,900 square nautical miles of critical marine habitat, including coral reef, hard bottom, seagrass meadow, mangrove communities and sand flats. NOAA and the state of Florida manage the sanctuary.

The full report can be found online: http://sanctuaries.noaa.gov/science/conservation/ncontrol.html

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Salmon fisheries: New findings about the early stages of IPN virus infection

ScienceDaily (Dec. 29, 2010) — Infectious pancreatic necrosis is a serious disease that leads to enormous losses in the salmon industry each year. The virus that causes the disease, IPN, is very prevalent in farmed salmon and trout in Norway. The virus attacks a wide diversity of hosts and has been found to occur in many different fish species, in addition to shellfish and molluscs. Fish that survive an IPN infection often become bearers of the virus and these fish are a potential source of infection to other individuals.

Irene ?rpetveit's doctoral research, carried out at The National Veterinary Institute, studied molecular mechanisms in the early stages of an IPN virus infection. All viruses are dependent on host cells in order to reproduce. Knowledge about how a virus enters its host's cells can lead to a better understanding of the disease and host range in addition to contributing to the development of more efficient vaccines and medicines. ?rpetveit found that the IPN virus attaches itself specifically to molecules on the surface of a number of different cell types. This indicates that the IPN virus uses an uptake mechanism that is activated by an external signal, for example, when a virus attaches itself to surface molecules.

We know that the IPN virus enters cells via vesicles or membrane bladders, which are then detached from the cell membrane. ?rpetveit has studied these vesicles more closely and found that the IPN virus is not dependent on a low pH level while this uptake mechanism is in progress. This is an important step towards the identification of the uptake mechanism used by the virus. She has also studied IPN-virus infection in cells that are assumed to be non-receptive and the results of her study can provide new information both about uptake mechanisms and about host range.

During one stage of this doctoral research, a molecular biological method was developed -- a so-called real-time reverse transcription-polymerase chain reaction (real-time RT-PCR). In order to validate and enhance this method, and as part of a larger project, it was compared with virus isolation in cell cultures, which is the traditional method used for detecting the IPN virus.

As part of this study, ?rpetveit examined the distribution of the IPN virus in various parts of the salmon's kidneys. The results of her study show that the head kidney and middle kidney contain approximately the same amount of the virus. This is good news for those who take samples for IPN tests in the field because taking samples from the head kidney is more time-consuming than from the middle kidney. At the same time, ?rpetveit's experiments showed that taking samples from the tail kidney should be avoided.

?rpetveit tested the effect of different preservation and storage procedures on parallel head kidney samples. Samples for IPN virus tests are usually preserved either on a modified cell culture medium (transport medium) or in RNAlater®, which is a commercial, RNA-stabilising reagent. ?rpetveit's work reveals how some methods of conserving and storing kidney samples from fish carrying the virus can directly influence test outcomes by giving falsely negative results.

Based on the results of this study, it is recommended that samples that are stored by using a transport medium should be homogenized immediately on arrival at the laboratory. Samples must always be stored at a temperature of minus 80°C.

Kidney tissue submerged in RNAlater® can only be analysed by using molecular biological methods, such as real-time RT-PCR. Storage of kidney tissue in RNAlater® is no better than in a transport medium, and this indicates that it is only necessary to use the former when there is a high risk of transport to the laboratory being delayed.

Real-time RT-PCR is shown to be at least as sensitive as traditional virus isolation in cell cultures when it comes to detecting the IPN virus. Real-time RT-PCR is also much less expensive and time-consuming. In the long term, real-time RT-PCR will therefore be employed for diagnostic purposes and, for example, for studies of brood fish and fry that are too small for pathological examination.

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What triggers mass extinctions? Study shows how invasive species stop new life

ScienceDaily (Dec. 31, 2010) — An influx of invasive species can stop the dominant natural process of new species formation and trigger mass extinction events, according to research results published December 29 in the journal PLoS ONE. The study of the collapse of Earth's marine life 378 to 375 million years ago suggests that the planet's current ecosystems, which are struggling with biodiversity loss, could meet a similar fate.

Although Earth has experienced five major mass extinction events, the environmental crash during the Late Devonian was unlike any other in the planet's history. The actual number of extinctions wasn't higher than the natural rate of species loss, but very few new species arose.

"We refer to the Late Devonian as a mass extinction, but it was actually a biodiversity crisis," said Alycia Stigall, a scientist at Ohio University and author of the PLoS ONE paper.

"This research significantly contributes to our understanding of species invasions from a deep-time perspective," said Lisa Boush, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

"The knowledge is critical to determining the cause and extent of mass extinctions through time, especially the five biggest biodiversity crises in the history of life on Earth. It provides an important perspective on our current biodiversity crises."

The research suggests that the typical method by which new species originate--vicariance--was absent during this ancient phase of Earth's history, and could be to blame for the mass extinction.

Vicariance occurs when a population becomes geographically divided by a natural, long-term event, such as the formation of a mountain range or a new river channel, and evolves into different species. New species also can originate through dispersal, which occurs when a subset of a population moves to a new location.

In a departure from previous studies, Stigall used phylogenetic analysis, which draws on an understanding of the tree of evolutionary relationships to examine how individual speciation events occurred.

She focused on one bivalve, Leptodesma (Leiopteria), and two brachiopods, Floweria and Schizophoria (Schizophoria), as well as a predatory crustacean, Archaeostraca. These small, shelled marine animals were some of the most common inhabitants of the Late Devonian oceans, which had the most extensive reef system in Earth's history.

The seas teemed with huge predatory fish such as Dunkleosteus, and smaller life forms such as trilobites and crinoids (sea lilies). The first forests and terrestrial ecosystems appeared during this time; amphibians began to walk on land. As sea levels rose and the continents closed in to form connected land masses, however, some species gained access to environments they hadn't inhabited before.

The hardiest of these invasive species that could thrive on a variety of food sources and in new climates became dominant, wiping out more locally adapted species. The invasive species were so prolific at this time that it became difficult for many new species to arise.

"The main mode of speciation that occurs in the geological record is shut down during the Devonian," said Stigall. "It just stops in its tracks."

Of the species Stigall studied, most lost substantial diversity during the Late Devonian, and one, Floweria, became extinct. The entire marine ecosystem suffered a major collapse. Reef-forming corals were decimated and reefs did not appear on Earth again for 100 million years. The giant fishes, trilobites, sponges and brachiopods also declined dramatically, while organisms on land had much higher survival rates.

The study is relevant for the current biodiversity crisis, Stigall said, as human activity has introduced a high number of invasive species into new ecosystems.

In addition, the modern extinction rate exceeds the rate of ancient extinction events, including the event that wiped out the dinosaurs 65 million years ago.

"Even if you can stop habitat loss, the fact that we've moved all these invasive species around the planet will take a long time to recover from because the high level of invasions has suppressed the speciation rate substantially," Stigall said.

Maintaining Earth's ecosystems, she suggests, would be helped by focusing efforts and resources on protection of new species generation. "The more we know about this process," Stigall said, "the more we will understand how to best preserve biodiversity."

The research was also funded by the American Chemical Society and Ohio University.

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Journal Reference:

Anna Stepanova, Alycia L. Stigall. Invasive Species and Biodiversity Crises: Testing the Link in the Late Devonian. PLoS ONE, 2010; 5 (12): e15584 DOI: 10.1371/journal.pone.0015584

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Teenage great white sharks are awkward biters

ScienceDaily (Dec. 2, 2010) — The jaws of adolescent great white sharks may be too weak to capture and kill large marine mammals, according to a new study published in the Journal of Biomechanics by an international team of scientists.

The researchers also found that, unlike mammals, sharks can maintain high bite forces no matter how widely their jaws are open, thanks to a unique jaw muscle arrangement that has helped them to be among the most successful predators of all time.

The study is the first of its kind to use sophisticated three-dimensional computer models and advanced engineering techniques to examine how different sharks hunt and kill prey.

Detailed computer simulations examined the feeding behaviour of two threatened shark species: the harmless grey nurse -- or sand tiger -- and the notorious great white.

Digital models revealed that the jaws of grey nurse sharks are spring-loaded for a rapid strike on small, fast-moving fish, while those of great whites are better suited for a powerful bite on prey ranging in size from small fish to large marine mammals.

"We were surprised that although the teeth and jaws of our sub-adult great white shark looked the part and the muscles were there to drive them, the jaws themselves just couldn't handle the stress associated with big bites on big prey," says study co-author Dr Stephen Wroe, who heads the Computational Biomechanics Research Group in the UNSW School of Biological, Earth and Environmental Sciences.

The reason for this appears to be that until great whites reach a length of about 3 metres or more their jaws haven't developed enough stiff mineralised cartilage to resist the forces involved.

The 2.5 metre great white shark used for the study was caught by the NSW Bather Protection Program. "It is hard to believe, but at this size great whites are basically just awkward teenagers that can't hunt large prey very effectively," says UNSW doctoral student Toni Ferrara, the lead author of the article. "It seems paradoxical that the iconic jaws of great white sharks -- made infamous by the classic Steven Spielberg movie Jaws -- are actually rather vulnerable when these sharks are young. Great white sharks are not born super-predators, they take years to become formidable hunters."

Co-author Dr Vic Peddemors, of the NSW Cronulla Fisheries Research Centre of Excellence, says: "This study may also explain why many of the shark attacks off NSW are aborted after a single exploratory bite, as the great whites involved are usually juveniles that might sustain jaw injury if they persevered with the attack.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of New South Wales, via EurekAlert!, a service of AAAS.

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Bering Sea chill yields fatter plankton, pollock diet changes

ScienceDaily (Dec. 11, 2010) — Despite a 30-year warming trend, the last three years in the Bering Sea have been the coldest on record. A University of Alaska Fairbanks scientist says that the cold temperatures have helped produce larger zooplankton in the Bering Sea, which may be changing the way Walleye pollock are feeding.

Alexei Pinchuk, research professional at the UAF Seward Marine Center, has spent the last three years gathering zooplankton samples in the Bering Sea. He and his colleagues have been looking at how changes in temperature in the Bering Sea affect resident zooplankton, and in turn how those zooplankton shifts may affect the diet of Walleye pollock.

During colder years, like the last three, pollock tend to eat the larger zooplankton, like copepods and krill, which flourish in chillier temperatures. Pinchuk has also found that the recent cold temperatures have brought an arctic "sand-flea," the amphipod Themisto libellula, south into Bering Sea waters.Young salmon and pollock seem to prefer to eat these amphipods over other, smaller zooplankton.

In warmer years, which include the record-setting high temperatures of 2001 to 2005, smaller zooplankton tend to thrive. According to Pinchuk and his colleagues, younger pollock tend to eat the smaller plankton, while larger pollock favor the larger plankton found in colder waters. This causes younger pollock to start out doing well in warmer temperatures, but as the pollock grow bigger, they may not be able to find the larger zooplankton prey they need to produce enough fat for overwintering.

"The larger pollock may then eat their smaller cousins instead," said Pinchuk.

Pinchuk conducted his research on board the U.S. Coast Guard Cutter Healy, R/V Knorr and R/V Thomas G. Thompson. He collected his zooplankton samples using multiple collecting nets.

Although the last few years have been cold, scientists predict that the warming trend in the Bering Sea will continue.

Pinchuk's findings were recently featured in the Nov. 4 issue of the journal Nature. His work is part of the broad Bering Sea Project, a six-year, $52 million integrated ecosystem study of the Bering Sea. The Bering Sea Project" is funded by both the National Science Foundation and the North Pacific Research Board.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Alaska Fairbanks.

Journal Reference:

Wendee Holtcamp. Marine science: The tiniest catch. Nature, 2010; 468 (7320): 26 DOI: 10.1038/468026a

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Growing hypoxic zones reduce habitat for billfish and tuna

ScienceDaily (Dec. 23, 2010) — Billfish and tuna, important commercial and recreational fish species, may be more vulnerable to fishing pressure because of shrinking habitat, according to a new study published by scientists from NOAA, The Billfish Foundation, and University of Miami Rosenstiel School of Marine and Atmospheric Science.

An expanding zone of low oxygen, known as a hypoxic zone, in the Atlantic Ocean is encroaching upon these species' preferred oxygen-abundant habitat, forcing them into shallower waters where they are more likely to be caught.

During the study, published recently in the journal Fisheries Oceanography, scientists tagged 79 sailfish and blue marlin with satellite tracking devices in the western North Atlantic, off south Florida and the Caribbean; and eastern tropical Atlantic, off the coast of West Africa. The pop off archival satellite tags monitored horizontal and vertical movement patterns. Researchers confirmed that billfish prefer oxygen rich waters closer to the surface and will actively avoid waters low in oxygen.

While these hypoxic zones occur naturally in many areas of the world's tropical and equatorial oceans, scientists are concerned because these zones are expanding and occurring closer to the sea surface, and are expected to continue to grow as sea temperatures rise.

"The hypoxic zone off West Africa, which covers virtually all the equatorial waters in the Atlantic Ocean, is roughly the size of the continental United States, and it's growing," said Dr. Eric D. Prince, NOAA's Fisheries Service research fishery biologist. "With the current cycle of climate change and accelerated global warming, we expect the size of this zone to increase, further reducing the available habitat for these fish."

Less available habitat can lead to more fish being caught since the fish are concentrated near the surface. Higher catch rates from these areas may give the false appearance of more abundant fish stocks. The shrinking availability of habitat and resulting increases to catch rates are important factors for scientists to consider when doing population assessments.

Researchers forecast that climate change and its associated rise in ocean temperatures will further increase the expansion of hypoxic zones in the world's oceans. As water temperature increases, the amount of oxygen dissolved in water decreases, further squeezing billfish into dwindling available habitat and exposing them to even higher levels of exploitation.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Oceanic and Atmospheric Administration.

Journal Reference:

Eric D. Prince, Jiangang Luo, C. Phillip Goodyear, John P. Hoolihan, Derke Snodgrass, Eric S. Orbesen, Joseph E. Serafy, Mauricio Ortiz and Michael J. Schirripa. Ocean scale hypoxia-based habitat compression of Atlantic istiophorid billfishes. Fisheries Oceanography, Volume 19, Issue 6 DOI: 10.1111/j.1365-2419.2010.00556

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To be or not to be endangered? Listing of rare Hawaiian coral species called into question

ScienceDaily (Dec. 2, 2010) — Coral reef ecosystems are one of the most diverse habitats on the planet, providing habitat for a wide variety of marine animals. Unfortunately, coral reefs and their associated fish, algae, and invertebrate species are in worldwide decline. In 2009, 83 rare corals were petitioned to be listed under the United States Endangered Species Act. The National Oceanic and Atmospheric Administration (NOAA) National Marine Fisheries Service is currently reviewing the status of the coral on the petition. If the listing is granted, it will afford higher protection and designate critical habitat for these corals. But are all the 'species' on this list really species?

A challenge to the evaluation is that coral "species" definitions are presently based on the coral skeleton, which can be so variable that it is often difficult to distinguish between groups. All 83 species on the petition can be found in the United States with 9 corals found in Hawai'i. Identifying which of the corals on this list are endemic (unique to each region), rare, or at risk of extinction, may prove difficult because it is not clear which corals interbreed. Scientists at the Hawai'i Institute of Marine Biology (HIMB), an organized research unit in the University of Hawai'i at M?noa's School of Ocean and Earth Science and Technology, examined the genetic and structural features of all the Hawaiian species from the common genus Montipora. Of these corals, three are under evaluation for listing under the Endangered Species Act (M. dilatata, M. flabellata, M. patula, more commonly known as Hawaiian Reef Coral, Blue Rice Coral, and Sandpaper Rice Coral). Surprisingly, researchers found that colony shape, color, and growth form can vary wildly, and may be misleading as to their species identity.

The seven Hawaiian coral species were found to belong to one of only four closely related genetic groups. Fine-scale measurements of the surface texture matched these genetic groups. Therefore, according to the genes and surface texture, this study revealed two previously unknown species complexes in Hawai'i; showing that corals previously thought to be very rare may interbreed with more common species. Dr. Zac Forsman at HIMB led the investigation, when asked about the recent discovery, he stated, "The scale of variation that corresponds to the species-level is not well understood in a lot of stony corals; this is a big problem for taxonomy and conservation. We need to determine if these species complexes contain species that are in the early process of forming, or if they just represent variation within a species. Either way, it could change our understanding of coral biodiversity." Co-author Dr. Rob Toonen added "this study builds on previous work by Forsman and colleagues showing that species designations in the coral genus Porites were not well-defined, either. As more studies like this are coming out, we are getting a clear picture that we don't really know which coral species names are valid and which are just different growth forms of common species."

The open access journal Public Library of Science One (PLoS One) will be publishing the full research report this month by Forsman, Concepcion, Haverkort, Shaw, Maragos, and Toonen.

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Effects of El Nino land South Pacific reef fish in hot water

ScienceDaily (Dec. 2, 2010) — Unseasonal warm temperatures caused by El Ni?o have a profound effect on the fish populations of coral reefs in the South Pacific, scientists have found. An international team of biologists studied the arrival of young fish to the atoll of Rangiroa in French Polynesia for four years and compared their results with satellite and oceanographic data. They found that the El Ni?o event caused a sudden collapse in the plankton community and this led to a near absence of the young fish that are required to replenish adult stocks.

Coral reef fishes are bad parents. Rather than caring for their young, they disperse them into the open waters off the reef where they drift with the currents while they grow and develop into small juveniles, at which point they make their way back again to the reef. This process allows these baby fish to feed on plankton and escape the predators that would consume them if they had to grow up on the reef with adults. But in a changing climate, this dispersal into the haven of open water could now become an Achilles' heel for coral reef fishes.

Using a crest net -- which looks like a football goalmouth facing out to sea on the edge of a barrier reef -- the scientists were able to monitor the numbers of fish as they returned to reefs from open water.

Under the supervision of Professor René Galzin, Dr Alain Lo-Yat and assistants from Service de la pêche set and emptied the net on the atoll of Rangiroa for four years, a period that included the intense 13-month El Ni?o event of 1997-8.

Climate scientist Elodie Martinez from France and marine biologists Dr Steve Simpson and Dr Mark Meekan then analysed the data, the longest time-series of its kind, to detect and explain the worrying trends. The paper is published in the journal Global Change Biology.

Dr Steve Simpson from the University of Bristol's School of Biological Sciences said: "Near to the equator, fish arrive throughout the year to replenish adult populations. In contrast, during the El Ni?o event at Rangiroa, when temperatures climbed up to 3.5°C above the seasonal average, we found that the young fish virtually disappeared.

"Analysis of satellite images around Rangiroa suggested that plankton, the food supply for many baby and adult reef fishes, declined dramatically during the warm waters of El Ni?o. As a consequence, adults struggled to produce offspring and young fishes were likely to starve when in open waters off reefs. Just 1-2 months after the onset of the warm conditions, the next generation of young fish stopped arriving so that adult stocks were no longer being re-supplied."

Dr Meekan said: "The events we witnessed during El Ni?o are a worrying sign for the future when climate change is predicted to warm ocean temperatures and may even increase the frequency of the El Ni?o phenomenon."

Warns Dr Simpson: "Coral reef fisheries provide food and livelihoods for hundreds of millions of people throughout the world and underpin a multi-billion dollar tourism industry. Our study shows that warmer waters may leave fish stocks on reefs in serious trouble, which will have far-reaching consequences for the people around the globe who are dependent upon them."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Bristol.

Journal Reference:

Alain Lo-Yat, Stephen D. Simpson, Mark Meekan, David Lecchini, Elodie Martinez, René Galzin. Extreme climatic events reduce ocean productivity and larval supply in a tropical reef ecosystem. Global Change Biology, 2010; DOI: 10.1111/j.1365-2486.2010.02355.x

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Sardine Run: Headlong race for survival of the species

ScienceDaily (Dec. 28, 2010) — Between May and July each year, millions of sardine move northward along the East coast of South Africa to reach spawning sites where they release their eggs. This is the spectacular Sardine Run. The migrating fish come under relentless attack from dolphins, sea lions, whales, tuna, birds and fishermen during their headlong, even suicidal race. Why do the sardine brave such formidable dangers? How did this dogged migration arise?

A great event, it has been stimulating scientists' imagination for many decades. Many hypotheses have been put forward, often contradictory ones. IRD researchers and their partners reviewed these different theories and tested them by comparing and combining a range of biological, acoustic, oceanographic and satellite data.

Inevitable return to their hatching place

Only a variably-sized proportion of the population of the South African sardine, Sardinops sagax, undertakes this long voyage, from the Agulhas Bank to grounds further North off Durban, in KwaZulu-Natal province. Like Emperor penguins in Antarctica, salmon in the rivers or indeed antelope across the African deserts, a single objective drives them: perpetuation of the species. Their reproductive instinct takes precedence over that for survival and pushes them along to overcome the many challenges in their way to return to their native area to scatter their eggs in the spawning grounds.

The logic is unyielding: if this homing strategy has worked for them, it will also succeed for their descendants. The resulting population balance justifies their efforts in the end. Great reproductive success wins out against the high mortality suffered during the migration. Releasing eggs further North, upstream of the ocean currents, ensures a better yield. Eggs, then larvae, thus have enough time to develop before they reach the Agulhas Bank. This bank is an extremely dispersive environment, where eggs or larvae become exposed to a high risk of being carried out to the open ocean, beyond the continental waters, and therefore lost to the species.

Permeation: the sixth sense of the sardine

How do the sardine manage to arrive each year exact at their own hatching site? Exchange mechanisms across its membrane allow permeation of the egg with components characteristic of the local marine ecosystem and with the terrestrial input from rivers. Then the same happens to the larvae. Olfactory processes are probably involved. Once adult, demonstrating exceptional sensory ability, the sardine pick up chemical stimuli coming from the local environment to guide themselves to their exact hatching site, in the KwaZulu-Natal.

In-bred heritage or loss of direction?

How have the sardine become fixed on an area so far North, near Durban, an environment so hostile to them? The research team decided on two hypotheses as being the most plausible.

The first suggests that this migration is a relict behaviour, probably inherited from the Last Ice Age. These sardine prefer sea temperatures of between 18 and 22°C. In those cold times they lived further North, off KwaZulu-Natal, where the ocean was colder than it is now. Then, the last deglaciation, brought on an overall warming of the seas. The fish therefore had to migrate towards the South, nearer the Pole. However, each year, in the reproductive season, they continued to come to the same place to spawn. That is why this ancient seasonal migration continues.

The second theory postulates that at a particular moment a shoal strayed off its normal migration route. Following some unusual oceanic conditions or a fault developed in the sardine's direction-finding system, their drift off-course led them to KwaZulu-Natal and resulted in an exceptional reproductive success. Two years later, the numerous descendants of this shoal, in their mature stage, repeated this epic voyage. From year to year, the population then grew, until it generated the enormous shoals we see today.

The efforts put in by the scientific community over the past five decades, summarized by this recent work, have substantially improved understanding of the ecological processes associated with the Sardine Run. This great migration route attracts a host of higher predators such as sharks, dolphins, whales and tuna, and generates a highly active fishing industry. Also, as a visually spectacular feature, it also stimulates tourism. Understanding how this extraordinary event of animal behaviour arose and why it persists would therefore help to meet some important economic necessities for the local communities.

These research studies were conducted jointly with the South African Departments of Agriculture, Forestry and Fisheries and of Environmental Affairs, the Universities of Cape Town and KwaZulu-Natal in South Africa and the South African Institute for Aquatic Biodiversity.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Institut de Recherche pour le Développement (IRD), via AlphaGalileo.

Journal Reference:

Fréon P., Coetzee J.-C., Van Der Lingen C.-D., Connell A.-D., O’Donoghue S.-H., Roberts M.-J., Demarcq H., Attwood C.-G., Lamberth S.-J. and Hutchings L. A review and tests of hypotheses about causes of the KwaZulu-Natal sardine run. African Journal of Marine Science, 2010; 32 (2): 449-479 DOI: 10.2989/1814232X.2010.519451

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When it comes to selecting a mate, the eyes have it

ScienceDaily (Dec. 13, 2010) — For the first time ever, scientists have found a difference in the way males and females of the same species of vertebrate see things -- and that sexes likely use that difference to select their mates.

Queen's PhD candidate Shai Sabbah, a Vanier Scholar, led a team of researchers who found that male and female cichlid fishes not only see things differently, but detect light in different ways as well.

"It is difficult to say what colour attracts the female the most, but we know that if we manipulate the colour of the fish by changing the light in the environment, the female fish will fail to choose a male of her own species," says Mr. Sabbah.

In nature, increased water turbidity due to deforestation and human development alters the visual environment of fish and consequently, impairs visually-mediated tasks such as mate choice. That can endanger the survival of the species and eventually lead to a reduction in diversity.

"These fish depend on colour vision for their own survival, so discovering differences in the highly dimensional visual systems of males and females is a significant finding," says Mr. Sabbah.

The research team also discovered that the fish have five different photoreceptor cones in their eyes, the most ever found in a vertebrate. Cones are what enable the eye to detect colours. Humans, by comparison, have just three photoreceptor cones. This gives cichlids the potential for very good discrimination between colours, which they need in order to choose a correct mate.

Cichlids are small, colourful fish found in many lakes around the world and in aquariums in North America. Female cichlids are dull in colour, while males are vibrant and often show colourful body markings.

Colour vision plays a key role in visual behavior. Mr. Sabbah and other members in Craig Hawryshyn's laboratory are currently looking at how differences in visual abilities affect the behavior of male and female cichlids.

The findings were recently published in BMC Biology, an online open access scientific journal that publishes original, peer-reviewed research in all fields of biology.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Queen's University.

Journal Reference:

Shai Sabbah, Raico Laria, Suzanne M Gray, Craig W Hawryshyn. Functional diversity in the color vision of cichlid fishes. BMC Biology, 2010; 8 (1): 133 DOI: 10.1186/1741-7007-8-133

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Drifting fish larvae allow marine reserves to rebuild fisheries

ScienceDaily (Dec. 26, 2010) — Marine ecologists at Oregon State University have shown for the first time that tiny fish larvae can drift with ocean currents and "re-seed" fish stocks significant distances away -- more than 100 miles in a new study from Hawaii.

The findings add credibility to what scientists have believed for some time, but until now been unable to directly document. The study also provides a significant demonstration of the ability of marine reserves to rebuild fishery stocks in areas outside the reserves.

The research appears in PLoS ONE, published by the Public Library of Science.

"We already know that marine reserves will grow larger fish and some of them will leave that specific area, what we call spillover," said Mark Hixon, a professor of marine biology at OSU. "Now we've clearly shown that fish larvae that were spawned inside marine reserves can drift with currents and replenish fished areas long distances away.

"This is a direct observation, not just a model, that successful marine reserves can sustain fisheries beyond their borders," he said. "That's an important result that should help resolve some skepticism about reserves. And the life cycle of our study fish is very similar to many species of marine fish, including rockfishes and other species off Oregon. The results are highly relevant to other regions."

The findings were based on the creation in 1999 of nine marine protected areas on the west coast of the "big island" of Hawaii. They were set up in the face of serious declines of a beautiful tropical fish called yellow tang, which formed the basis for an important trade in the aquarium industry.

"This fishery was facing collapse about 10 years ago," Hixon said. "Now, after the creation of marine reserves, the fishery is doing well."

The yellow tang was an ideal fish to help answer the question of larval dispersal because once its larvae settle onto a reef and begin to grow, they are not migratory, and live in a home range about half a mile in diameter. If the fish are going to move any significant distance from where they are born, it would have to be as a larva -- a young life form about the size of a grain of rice -- drifting with the currents for up to two months before settling back to adult habitats.

Mark Christie, an OSU postdoctoral research associate and lead author of the study, developed some new approaches to the use of DNA fingerprinting and sophisticated statistical analysis that were able to match juvenile fish with their parents, wherever they may have been from. In field research from 2006, the scientists performed genetic and statistical analyses on 1,073 juvenile and adult fish, and found evidence that many healthy juvenile fish had spawned from parents long distances away, up to 114 miles, including some from marine protected areas.

"This is similar to the type of forensic technology you might see on television, but more advanced," Christie said. "We're optimistic it will help us learn a great deal more about fish movements, fishery stocks, and the genetic effects of fishing, including work with steelhead, salmon, rockfish and other species here in the Pacific Northwest."

This study should help answer some of the questions about the ability of marine reserves to help rebuild fisheries, the scientists said. It should also add scientific precision to the siting of reserves for that purpose, which is just one of many roles that a marine reserve can play. Many states are establishing marine reserves off their coasts, and Oregon is in the process of developing a limited network of marine reserves to test their effectiveness. The methods used in this study could also become a powerful new tool to improve fisheries management, Hixon said.

"Tracking the movement of fish larvae in the open ocean isn't the easiest thing in the world to do," Hixon said. "It's not like putting a radio collar on a deer. This approach will provide valuable information to help optimize the placement of reserves, identify the boundaries of fishery stocks, and other applications."

The issue of larval dispersal is also important, the researchers say, because past studies at OSU have shown that large, fat female fish produce massive amounts of eggs and sometimes healthier larvae than smaller fish. For example, a single two-foot vermillion rockfish produces more eggs than 17 females that are 14 inches long.

But these same large fish, which have now been shown to play key roles in larval production and fish population replenishment, are also among those most commonly sought in fisheries.

The study was done in collaboration with the University of Hawaii, Washington State University, National Marine Fisheries Services and the Hawaii Department of Natural Resources. It was funded by Conservation International.

"The identification of connectivity between distant reef fish populations on the island of Hawaii demonstrates that human coastal communities are also linked," the researchers wrote in their conclusion. "Management in one part of the ocean affects people who use another part of the ocean."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Oregon State University.

Journal Reference:

Sharyn Jane Goldstien, Mark R. Christie, Brian N. Tissot, Mark A. Albins, James P. Beets, Yanli Jia, Delisse M. Ortiz, Stephen E. Thompson, Mark A. Hixon. Larval Connectivity in an Effective Network of Marine Protected Areas. PLoS ONE, 2010; 5 (12): e15715 DOI: 10.1371/journal.pone.0015715

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Singing fish: Choir of electric fish makes debut in interactive 'scale' exhibit at Netherlands festival

ScienceDaily (Dec. 22, 2010) — Three Northwestern University faculty members recently presented their collaborative "singing electric fish" installation to thousands of people attending the STRP Festival, one of the largest art and technology festival venues in Europe. Many visitors had the chance to grab a baton and direct the unusual choir.

The audience-interactive exhibit, titled "scale," had its world premiere in November at the 10-day festival held in Eindhoven, The Netherlands.

The multidisciplinary artwork was created by neurobiologist and engineer Malcolm MacIver, visual and conceptual artist Marlena Novak and composer and sound designer Jay Alan Yim. In the installation, 12 different species of electric fish from the Amazon River Basin comprise a "choir" whose sonified electrical fields provide the source tones for an immersive audiovisual experience.

Participants act as conductors, using a modified Nintendo Wii remote. Each "conductor" can cue an individual fish or combine the sounds of several fish together, either in natural or digitally processed modes. The otherworldly sounds are heard through a spatialized audio system; a touch-screen panel allows for changes in volume. Arrays of light-emitting diodes under each tank provide visual feedback to visitors.

The work is designed to offer multiple levels of aesthetic experience. "Initially there is an audiovisual encounter with the dynamically interactive sound sculpture," Novak said. "As one goes to the next level of active participation, there is a sense of personal engagement for each individual who uses the interface directly to 'conduct' the ensemble of fish. The system allows for an additional degree of collaboration when more than one person manipulates the touch-screen at the same time."

The team hopes to foster wider public awareness of the scientific contributions of the electric fish and the fragility of their Amazonian environment. "These remarkable fish have contributed greatly to our understanding of how the brain works, yet few people outside of specialists have heard of them," said MacIver, associate professor of biomedical and mechanical engineering in the McCormick School of Engineering and Applied Science.

The fish are housed in individual tanks arranged in an arc and outfitted with a 12-channel speaker array, with the conductor's podium in the middle. Each fish continually discharges a weak electric field of constant frequency; this field is picked up by sensors and then amplified. By playing these signals through a speaker, a tone corresponding to the field can be heard. The resulting sound from each fish varies (due to species-specific variations in the emitted field), falling within the range of 30 to 1,700 hertz -- from the lowest B natural on a piano to the G-sharp key six octaves higher.

MacIver, Novak and Yim worked together on every major aspect of the work, each bringing complementary skills to the project. MacIver's research focuses on sensory processing and locomotion in electric fish; Novak and Yim, collaborating as localStyle, make intermedia works motivated by the theme of perception and that explore topics such as boundaries relating to physical and intangible properties.

Novak is a faculty member in the department of art theory and practice in the Weinberg College of Arts and Sciences. Yim is an associate professor of composition at the Bienen School of Music.

The lead technician for scale was Northwestern alumnus Kyle Liske. "We were lucky to find Kyle just as he was completing his engineering degree here at McCormick," MacIver said. "He transitioned from being a student assistant for scale to working full time on the project in March. Kyle has been an outstanding asset for the project." Several faculty members provided important technical guidance, MacIver added, including Michael Peshkin, professor of mechanical engineering.

During the exhibit at the STRP Festival, MacIver, Novak and Yim were on hand to share information with visitors about how electric fish use the discharges to explore their environment, the murky waters of the Amazon.

Thousands of scientific papers on neural processing of sensory information in these fish have pushed forward our understanding of the brain. "For example, in all animals, including humans, most of the input to our sensory systems is due to our own movement," MacIver said. "The neural mechanism for subtracting this self-generated sensory information has been decoded in the electric fish and is likely to be similar to certain circuits in our own brain that performs the same function. This is key to remaining sensitive to things happening around us."

An understanding of the way in which the fish move and sense is also inspiring the development of a new generation of highly maneuverable underwater vehicles, which use weak electric fields to sense things the way the fish does and a propulsion system based on what the fish uses. These vehicles are needed for things like long-term environmental monitoring and for dealing with underwater problems, such as the recent Gulf of Mexico oil spill.

scale was funded by the Northwestern Center for Interdisciplinary Research in the Arts, the Walter P. Murphy Society, the University Research Grants Committee and the National Science Foundation.

Nearly 30,000 people attended this year's festival. STRP stands for Strijp-S, the name of the industrial site where Philips invented such items as the audiocassette and the CD. The city of Eindhoven is referred to as the "Brainport" of the Netherlands due to the many scientific and technological institutes located in the area.

In addition to technological innovations, Philips sponsored one of the pioneering landmarks of intermedia art in 1958: the famous pavilion designed by Le Corbusier and Iannis Xenakis, in collaboration with the 350-speaker "Poème Electronique" by Edgard Varèse, plus projections and ambient light sequences. This amplifies the Netherlands' tradition of supporting arts and technology by institutes such as V2 (Rotterdam), Sonology (The Hague), STEIM and NIMK (both Amsterdam).

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Northwestern University. The original article was written by Megan Fellman.

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Wild salmon decline was not caused by sea lice from farm salmon, new research suggests

ScienceDaily (Dec. 13, 2010) — A new UC Davis study contradicts earlier reports that salmon farms were responsible for the 2002 population crash of wild pink salmon in the Broughton Archipelago of western Canada.

The Broughton crash has become a rallying event for people concerned about the potential environmental effects of open-net salmon farming, which has become a $10 billion industry worldwide, producing nearly 1.5 million tons of fish annually.

The new study, to be published online this week in Proceedings of the National Academy of Sciences, does not determine what caused the crash, but it acquits the prime suspect: small skin parasites called sea lice.

The study's lead author is Gary Marty, a veterinary pathologist and research associate at the UC Davis School of Veterinary Medicine. An expert in fish diseases, Marty has been studying the health of pink salmon since the 1989 Exxon Valdez oil spill in Alaska.

"For anybody concerned about the effect of farm salmon on wild salmon, this is good news," Marty said. "Sea lice from fish farms have no significant effect on wild salmon population productivity."

The new study is the first to analyze 20 years of fish production data and 10 years of sea-lice counts from every salmon farm in the Broughton Archipelago and compare them against 60 years of population counts of adult pink salmon.

The study concludes that farm fish are indeed the main source of sea lice on the area's juvenile wild pink salmon, but it found no statistical correlation between lice levels on the farms and the lifetime survival of wild pink salmon populations.

Pink salmon (Oncorhynchus gorbuscha) are the most abundant wild salmon species in the Broughton Archipelago. When they are a few months old, juvenile pink salmon leave the streams where they were born. They mature at sea, then return to their native streams to spawn and die two years after their parents.

Because of their two-year lifespans, the pink salmon born in odd-numbered years are genetically different from those born in even-numbered years. In the 60-year record, both lines of pink salmon have had tremendous, unexplained population swings, even before fish farms were established in the late 1980s.

Sea lice are natural parasites of adult pink salmon. The adult louse, about the size of a small watermelon seed, attaches itself to a fish's skin and feeds on its host. Minor lice infestations are not harmful to pink salmon, but a severe infestation can weaken or kill the smallest fish (those about the size of a paperclip). On fish farms, veterinarians treat the fish with medicated feed when lice populations become too high.

The Broughton fish farms raise Atlantic salmon (Salmo salar) in net-sided pens in the water. Wild pink salmon are separated from the farm fish only by the mesh of the net enclosures. Lice freely pass from wild fish to farm fish, and vice-versa.

Record high numbers of wild pink salmon returned to spawn in rivers of the Broughton Archipelago in 2000 and 2001, but only 3 percent of that number returned in 2002, and only 12 percent in 2003.

Also, in 2001, the first examination of Broughton juvenile pink salmon found that more than 90 percent had lice. In the next two years, when the salmon numbers plummeted, the hypothesis arose that sea lice from fish farms were to blame.

Calls went up for the farms to move the fish from open-net pens to closed containers. And government regulators ordered farmers to use stricter anti-lice treatments.

In the new study, Marty and his colleagues were able to see, year by year, how many lice were on the farms when the young pink salmon went to sea, and how many of those salmon returned to spawn. The results were surprising.

"The salmon that returned in such low numbers in 2002 were exposed as juveniles to fewer sea lice than were the salmon that returned in record high numbers in 2001," Marty said. "Sea lice from farm fish could not have caused the 2002 wild salmon population crash."

Marty's co-authors are Sonja Saksida, director of the British Columbia Centre for Aquatic Health Sciences in Campbell River, and Terrance Quinn, professor of fish population dynamics at the Juneau Center of the School of Fisheries and Ocean Sciences at the University of Alaska Fairbanks. Quinn is a world authority on mathematical modeling of fish populations. Saksida is a veterinarian and the first researcher given access to confidential records from all the Broughton aquaculture companies.

Marty is also the fish pathologist for the British Columbia Ministry of Agriculture and an affiliate faculty member of the University of Alaska School of Fisheries and Ocean Sciences.

Marty said that even though the trio used much of the same fish and lice data used in previous studies, they reached a different conclusion for two reasons: First, the fish farmers gave Saksida their records, and second, the old and new data were analyzed using methods common in veterinary medical science that were not used in many of the previous studies.

"The major lesson of this study is that we cannot settle for simple explanations for wild-animal population declines. There are very complex interactions among disease, environment and animal population health. Sustainability studies must engage all the science specialties to pursue a better understanding of these relationships," Marty said.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of California - Davis.

Journal Reference:

G. D. Marty, S. M. Saksida, T. J. Quinn. Relationship of farm salmon, sea lice, and wild salmon populations. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1009573108

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New fossil site in China shows long recovery of life from the largest extinction in Earth's history

ScienceDaily (Dec. 23, 2010) — A major new fossil site in south-west China has filled in a sizeable gap in our understanding of how life on this planet recovered from the greatest mass extinction of all time, according to a paper co-authored by Professor Mike Benton, in the School of Earth Sciences, and published in the Proceedings of the Royal Society B. The work is led by scientists from the Chengdu Geological Center in China.

Some 250 million years ago, at the end of the time known as the Permian, life was all but wiped out during a sustained period of massive volcanic eruption and devastating global warming. Only one in ten species survived, and these formed the basis for the recovery of life in the subsequent time period, called the Triassic. The new fossil site -- at Luoping in Yunnan Province -- provides a new window on that recovery, and indicates that it took about 10 million years for a fully-functioning ecosystem to develop.

"The Luoping site dates from the Middle Triassic and contains one of the most diverse marine fossil records in the world," said Professor Benton. "It has yielded 20,000 fossils of fishes, reptiles, shellfish, shrimps and other seabed creatures. We can tell that we're looking at a fully recovered ecosystem because of the diversity of predators, most notably fish and reptiles. It's a much greater diversity than what we see in the Early Triassic -- and it's close to pre-extinction levels."

Reinforcing this conclusion is the complexity of the food web, with the bottom of the food chains dominated by species typical of later Triassic marine faunas -- such as crustaceans, fishes and bivalves -- and different from preceding ones.

Just as important is the 'debut' of top predators -- such as the long-snouted bony fish Saurichthys, the ichthyosaur Mixosaurus, the sauropterygian Nothosaurus and the prolacertiform Dinocephalosaurus -- that fed on fishes and small predatory reptiles.

Professor Shixue Hu of the Chengdu Group said: "It has taken us three years to excavate the site, and we moved tonnes of rock. Now, with thousands of amazing fossils, we have plenty of work for the next ten years!"

"The fossils at Luoping have told us a lot about the recovery and development of marine ecosystems after the end-Permian mass extinction," said Professor Benton. "There's still more to be discovered there, and we hope to get an even better picture of how life reasserted itself after the most catastrophic global event in the history of our planet."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Bristol.

Journal Reference:

Shi-Xue Hu, Qi-Yue Zhang, Zhong-Qiang Chen, Chang-Yong Zhou, Tao Lü, Tao Xie, Wen Wen, Jin-Yuan Huang, Michael J. Benton. The Luoping biota: exceptional preservation, and new evidence on the Triassic recovery from end-Permian mass extinction. Proceedings of the Royal Society B, 2010; DOI: 10.1098/rspb.2010.2235

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Shy trout size it up

ScienceDaily (Dec. 7, 2010) — Personality is not just a feature unique to humans and pets. Scientists at the University of Gothenburg (Sweden) have revealed that also brown trout have individual characters and show different personalities.

Researcher Bart Adriaenssens from the Department of Zoology at the University of Gothenburg has for many years studied the behaviour of juvenile trout from watercourses on the west coast of Sweden.

"My results show that it are not just humans and other mammals that exhibit personality. Also brown trout differ among each other in their level of aggression and react differently to changes in their surroundings," says Bart Adriaenssens. "The release of a novel object in the aquarium causes very different reactions. Some individuals will immediately explore this object, whereas others will rather hide in a corner and try to avoid every contact."

"But it are not always the bold and aggressive fish who are most successful. When we marked trout individually and released them back in the wild, it were shy trout who grew most rapidly."

Which fish personality works best may also depend on the environment: if there is little protection available, as is the case, for example, in a tank at an aquaculture facility, large and bold fish are likely able to grab most of the food. But in the more complex environment of a stream in the wild, shy individuals can be more successful.

The question of why animals have personalities remains still to be answered. "If a certain personality proves to work well, and individuals with that personality grow rapidly, survive in greater numbers and have more offspring, we would expect all individuals to behave according to that personality. This is not the case, however, and there is still a lot of work to be done in this area to explain why," says Bart Adriaenssens.

The thesis has been successfully defended.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Gothenburg, via EurekAlert!, a service of AAAS.

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