Progress on vaccine for 'Ich,' bane of fish farms and home aquarium hobbyists

ScienceDaily (Aug. 30, 2010) — Tests of the potential vaccine against "Ich" ? the dreaded "white-spot" disease that plagues fish in commercial fish farms, public aquariums, pet fish retail outlets, and home aquariums ? are raising hopes for finally controlling the disease, scientists reported at the 240th National Meeting of the American Chemical Society (ACS).

"Outbreaks of the parasitic disease caused by Ichthyophthirius (Ich) can result in losses of 50-100 percent of fish," Dehai Xu, Ph.D., said in presenting the results. "The disease is very common, and almost every home fish hobbyist has encountered it. Once the parasite infects fish, and starts growing in the skin, fins, and gills, there is no really effective treatment. Ich causes losses estimated at $50 million annually. It would be much better to prevent the disease."

As an indication of the difficulty in treating Ich outbreaks, Xu used the example of an infection that strikes a commercial fish farming pond, which might have a surface area equal to 10 or 20 high school football fields. The typical treatment involves pouring in a solution of formaldehyde, a potentially toxic substance. Hundreds of gallons might be needed, and farmers might have to repeat the treatment several times. Even after treatment, the fish would be at risk of reinfection if they encountered the parasite again, he said.

"To vaccinate against Ich, you would need much less medication, and it would not pose an apparent threat to the environment," Xu pointed out. "And you would need just one treatment to make the fish immune for life."

Xu explained that efforts to develop an Ich vaccine have focused on use of so-called "trophonts," which are the infective stage of the Ich parasite's life cycle. Trophonts burrow into a fish's skin, fins, and gills, causing the white skin spots characteristic of the disease. Those efforts have been hindered, however, by gaps in scientific knowledge about how fish develop protective immunity to trophonts. Xu and colleagues, Drs. Phillip Klesius and Craig Shoemaker, who are with the U. S. Department of Agriculture's Agricultural Research Service (ARS) in Auburn, Al., set out to fill those gaps.

Their study evaluated influence of vaccine formulation and doses of vaccine on protective immunity of channel catfish against Ich. The results showed that vaccination with live Ich theronts and trophonts killed with high-frequency sound waves stimulated production of protective antibodies in the catfish.

"This study demonstrated that vaccines against Ich induced protective immunity and could provide a unique solution to prevent this parasitic disease through vaccination," Xu said. "An Ich vaccine would have great impact by preventing the disease, minimizing loss of valuable fish and increasing profitability of aquaculture."

Xu noted that the study was a small, laboratory-scale endeavor, with unsolved problems on the road ahead to a commercial vaccine. One, for instance, involves producing a large quantity of Ich antigen for the vaccine and then formulating a vaccine that can be easily administered to large numbers of fish in a "bath" or in food, rather than by injection. In the bath approach, fish would be kept in a container or an enclosure with water containing the vaccine. This study is within the component of ARS National Program 106-"Aquaculture" to improve health and welfare of aquatic animals. Xu and colleagues hope their study will bring more attention to the research to combat this disease.

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China tops world in catch and consumption of fish

ScienceDaily (Sep. 23, 2010) — China leads the world in tonnage of fish caught annually as well as the amount of fish consumed, according to new findings.

The research, conducted by the University of British Columbia in collaboration with the National Geographic Society and The Pew Charitable Trusts, ranks the top 20 nations that have the greatest impact on ocean ecosystems through catching or consuming marine wildlife.

China's top ranking results from its enormous population, despite its very low per capita footprint of fish catch and consumption. Japan is high on the list too, a result of its rate of consumption (often by importation) of fish rather than its catch. The "top 20" lists of fish catch and consumption are published in the October issue of National Geographic magazine.

The United States comes in third in both lists, due to its relatively large population and tendency to eat top predator fish such as Atlantic salmon. Peru ranks second in the world in catch though is not in the top 20 fish-consuming countries because Peruvians on the whole eat little seafood.

The data come from the SeafoodPrint study, led by Daniel Pauly of the University of British Columbia and National Geographic Ocean Fellow Enric Sala.

In assessing the true impact nations have on the seas, the team needed to look not just at what a given nation caught but also at what the citizens of that nation ate.

Standard methods of measuring nations' impact on the sea are misleading because, as Pauly says, "every fish is different. A pound of tuna represents roughly a hundred times the footprint of a pound of sardines."

That's because fish like tuna are apex predators -- they feed at the very top of the food chain. The largest tuna eat enormous amounts of fish, including intermediate-level predators such as mackerel, which in turn feed on fish like anchovies, which prey on microscopic organisms. A large tuna must eat the equivalent of its body weight every 10 days to stay alive, so a single thousand-pound tuna might need to eat as many as 15,000 smaller fish in a year, the National Geographic article says.

Any large fish in the world -- a Pacific swordfish, an Atlantic mako shark, an Alaska king salmon, a Chilean sea bass -- is likely to depend on several levels of a food chain.

The SeafoodPrint method provides a way to compare all types of fish caught, by creating a unit of measurement based on "primary production" -- the microscopic organisms at the bottom of the marine food web -- required to make a pound of a given type of fish. The research found that a bluefin tuna, for example, may require a thousand pounds or more of primary production.

"The SeafoodPrint allows us to directly compare a sardine fishery with a tuna fishery, because each is measured according to the primary production it represents," Pauly says.

The new approach also allows the researchers to assess individual nations' impacts on the seas, based not only on what was caught but also on what their citizens ate through imports. "A country can acquire primary production by fishing, or it can acquire it by trade," says Pauly, whose research is part of the Sea Around Us project of The Pew Charitable Trusts and the University of British Columbia.

Much of the world's catch, especially from the high seas, is being purchased by wealthy nations for their people; poorer countries simply can't afford to bid for high-value species, the article says. Citizens in poor nations also lose out if their governments enter into fishing or trade agreements with wealthier nations. In these cases, local fish are sold abroad and denied to local citizens -- those who arguably have the greatest need to eat them and the greatest right to claim them.

Humanity's demand for seafood has now driven fishing fleets into every virgin fishing ground in the world, the scientists say. A report by the World Bank and United Nations' Food and Agriculture Organization suggests that even if the number of boats, hooks and nets now used were cut by half, the world would still end up catching too many fish to be sustainable for the future.

The scientists favor treaties among nations setting seafood-consumption targets as well as ocean havens to safeguard resources. "Barely one percent of the ocean is now protected, compared with 12 percent of the land," Sala says, "and only a fraction of that is fully protected."

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Supercomputers help track species affected by Gulf oil spill

ScienceDaily (Aug. 26, 2010) — To establish a baseline for measuring and predicting the biological impact of the Deepwater Horizon oil spill, a LSU ichthyologist and an Ohio biomedical informatics researcher are using Ohio Supercomputer Center, or OSC, systems to help map data on the extent of the spill and chemicals and the distribution of various fish species.

"We know very little about deep-sea life and even less about the interactions between this biota and these toxic chemicals," said Prosanta Chakrabarty, curator of ichthyology at LSU's Museum of Natural Science. "The northern Gulf of Mexico is home to more than 600 species of fish, and new ones are being described every year. Through our efforts and by making the informatics tools available over the web, our aim is to map baseline data about nearly every northern Gulf of Mexico species that may be impacted."

Several universities and federal agencies, including NASA, NOAA and USGS, are focused on tracking the oil and dispersants on the surface of the Gulf and in shallow waters and marshes. To complement these efforts, the researchers are repurposing a computer application that was designed to track infectious diseases to collect and reinterpret data for oil, dispersants and fish, including those at great depth.

"We have developed DEPTHMAP (depthmap.osu.edu), a web-accessible mapping application for historical species collection records, to combine baseline information about the range of these species with respect to data on the extent of the spill," said Daniel Janies, associate professor of Biomedical Informatics at The Ohio State University. "From museum records, wildlife and fisheries collections data, we can measure the impact of this spill on marine species with various habitats, life histories and ranges."

Janies has created several applications to track the avian influenza virus (H5N1) -- and, more recently, to monitor the H1N1 virus -- on a real-time geographic information system. Janies and his colleagues teamed up with OSC staff to tune these codes to run on the center's IBM Cluster 1350 Glenn system, which features 9,500 cores and 24 terabytes of memory.

Now, wildlife data are being mapped onto a similar real-time geographic information system to show researchers which species' habitats are located in the region of the Gulf affected by the spill over time.

"Without historical baseline data like that we are mapping, future faunal surveys will not illustrate the impact of this deep-water oil spill," said Janies. "We will make the maps and underlying informatics tools we develop available to a wide community of users via the web, such that other resource managers and researchers can leverage our efforts for a wide variety of species of interest."

The species being tracked will include commercially important grouper, snapper and croaker species, as well as ecologically important species near the bottom or top of the food chain, including batfishes and sharks. Data collected at intervals since the spill began is being incorporated and compared to show changing distributions, deaths, lost spawning seasons and year classes, and, potentially, extinctions.

"Unfortunately, the deployment of an unprecedented amount of dispersant at the well-head a mile below the surface has created plumes of oil microdroplets that are known to be toxic," said Chakrabarty. "The majority of the millions of gallons of oil that was introduced to the Gulf environment resides subsurface. While treatment of the surface oil can be conducted by burning and skimming, there is no treatment for subsurface oil and no plans from BP or the federal or state government to treat subsurface oil."

Chakrabarty and Janies hope to collect and integrate several types of information during this project:

How the expanding spill will affect migrating and spawning organisms that travel through the Gulf. This information will help wildlife officials better manage these situations (e.g., saving vulnerable eggs and larvae of blue-fin tuna);Which species of organisms migrating at great depths will be most severely impacted by concentrated plumes of sub-surface oil and dispersant (e.g., pancake batfishes that feed on the vulnerable layer of plankton now covered in chemicals);The interaction between important fisheries and non-commercial and commercial fishes in sites of subsurface oil plumes (e.g., deep ocean coral species in Louisiana and Florida that are in the path of the plumes);How the plumes might affect the life-history stages of different fish species.

"Although the toxic effects of oil and dispersants and how they break down with sunlight are well understood, their effects below the surface are not known," said Chakrabarty. "Oil and dispersants break down in contact with sunlight and the rich microbial community of the warm waters near the surface. However, the deep sea is very cold, under high pressure and extremely dark. We don't know how oil and dispersants break down under these conditions, but evidence suggests that it will be incredibly slow."

Note: Co-developers of the application and its use cases include Jori Hardman, The Ohio State University, Biomedical Informatics; and Calvin Lam, The Ohio State University, Biomedical Informatics.

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Whale sharks may produce many litters from one mating, paternity test shows

ScienceDaily (Aug. 31, 2010) — How do female whale sharks meet their perfect mates and go on to produce offspring? While little is known about the reproductive behavior of these ocean-roaming giants, a newly published analysis led by University of Illinois at Chicago biologist Jennifer Schmidt reveals new details about the mating habits of this elusive, difficult-to-study fish.

Schmidt, a UIC associate professor of biological sciences, determined paternity of 29 frozen embryos saved from a female whale shark caught off the coast of Taiwan in 1995. The embryos, studied in collaboration with Professor Shoou-Jeng Joung at the National Taiwan Ocean University, are extremely rare.

The pregnant shark carried a surprisingly large number of embryos -- 304 -- still in the uterus and representing a spectrum of age and development stages ranging from being still egg-encased to developed, near-term animals.

Schmidt and her colleagues spent several years developing DNA genetic markers to study whale sharks, initially for population genetics, but in this study the tool was used to determine paternity.

Shark reproduction is still an emerging science, but what is known suggests that most broods are sired by more than one male. That is not what Schmidt found with this particular female whale shark.

"These differently aged embryos -- itself unusual across animal species -- had the same father," Schmidt said. "We have to be very cautious in drawing conclusions from a single litter, but the data suggest female whale sharks store sperm after a single mating event, and subsequently fertilize their own eggs as they are produced."

If the finding can be supported from analysis of other whale shark litters, Schmidt said, "it would suggest that there is no whale shark breeding ground where large numbers of animals meet to mate, but rather that mating occurs as an isolated event."

Follow-up studies may be serendipity. International protocols protect whale sharks from capture, few are housed in aquariums, and those that are are usually less than 25 years old and not yet sexually mature. Scientists typically study whale sharks at seasonal feeding grounds, but those animals are usually juveniles not mature enough to breed. Rarely are adult females observed in the wild.

"Protections for whale sharks have increased in many parts of the world, yet shark numbers seem to be declining, and the average size is getting smaller," said Mark Meekan, principal research scientist with the Australian Institute of Marine Sciences.

"This is a classic sign of overfishing, where larger, more valuable animals are selectively removed," he said. "Targeted fishing of breeding-age animals in a late-maturing species can be devastating for its survival."

The findings are reported in the journal Endangered Species Research, published online Aug. 4. Other authors include Meekan; Joung and Chien-Chi Chen of the National Taiwan Ocean University; Saad I. Sheikh, formerly of UIC; and Bradley Norman of ECOCEAN Inc.

The work was funded by a grant from Project Aware.

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

Journal Reference:

Schmidt et al. Paternity analysis in a litter of whale shark embryos. Endangered Species Research, 2010; 12 (2): 117 DOI: 10.3354/esr00300

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Salmon baby food? Babies need omega-3s and a taste for fish, scientist says

ScienceDaily (Aug. 24, 2010) — Has your toddler eaten fish today? A University of Illinois food science professor has two important reasons for including seafood in your young child's diet, reasons that have motivated her work in helping to develop a tasty, nutritious salmon baby food for toddlers.

"First, babies need a lot of the omega-3 fatty acids found in fish for brain, nerve, and eye development, and when they switch from breast milk or formula to solid food, most of them don't get nearly enough," said Susan Brewer, also a registered dietitian.

"Second, children's food preferences are largely developed by the time they're five, so I urge parents to help their kids develop a taste for seafood early," she said.

Fish that are high in omega-3 fatty acids, such as salmon, have huge health benefits and help to prevent coronary artery disease, but most adults don't eat fish twice weekly as experts recommend. In predisposing children toward liking fish, parents are doing their kids a big favor, she said.

Brewer knows her recommendations might meet with some resistance. "When we started working on salmon baby food, I thought, Ewwwh! But the American Heart Association and the American Academy of Pediatrics is solidly behind the idea, and fish-based baby foods, common in Asian markets, have been marketed successfully in the United Kingdom and Italy."

Brewer collaborated with former U of I professor Peter Bechtel, now of Alaska's Agricultural Research Service, in the effort to create a viable product, using wild-caught salmon from Alaskan waters.

"When salmon swim upstream to spawn, their flesh begins to get very soft. At that point, the meat is not firm enough for fillets, but it's perfect for baby food," she noted.

She has experimented with both pink and red salmon, finding that red salmon survives the baby food production process better.

And, to boost nutrition, in separate experiments she has added bone meal and pureed salmon roe (eggs) to her entrees. The first ingredient (made by grinding the bones in the salmon into a powder) provides calcium in a form that is readily available for bone building in children. The second provides high-quality protein and contains significant quantities of vitamin D and omega-3 fatty acids, particularly docohexaenoic acid (DHA).

"A newborn infant's brain is 50 percent DHA," she noted. "However, babies and toddlers have immature livers and can't synthesize enough DHA to ensure an adequate supply to their developing nerve tissues. If small children are going to get DNA, they must ingest it in their food."

According to Brewer, the results of her experiments have been encouraging. "Salmon is very mild, and the toddler dinners, which are 27 percent meat or fish, don't taste or smell fishy at all. They remind me of that salmon and cream cheese dip you have during the holidays."

Besides, could 107 parents of preschoolers be wrong? In a recent sensory panel conducted in the scientist's lab, parents found little difference in taste between formulations that contained roe or bone meal and those that didn't. Eighty-one percent of the parent panelists -- even those who don't eat salmon themselves -- said they would offer it to their children after taste testing the product.

"It's not enough for mothers to know that toddlers need fish in their diets. They won't buy a product unless it also appeals to the eye and the taste buds," she said.

"Our goal is to deliver maximum nutrition in an entrée that's aesthetically pleasing, and these studies show that we can do just that," she added.

The paper on including salmon roe in salmon baby food products was published in the May 2010 issue of the Journal of Food Science. The sensory panels study has been accepted for publication in an upcoming issue of the Journal of Food Science.

F.A. DeSantos of the U of I and P. Bechtel and S. Smiley of the University of Alaska, Fairbanks, are co-authors of both papers. L. Ramamoorthi of the U of I is an additional co-author of the sensory panel paper. Research for the studies was funded by USDA CSREES.

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