Supportive breeding with subsequent stocking is an important long-term conservation tool for sustaining harvestable populations and genetic diversity in wild fish populations.

I understand that the Challenger Institute of Technology was successfully breeding several popular fish species for wild stock enhancement. Their activity have since ceased largely due to the argument that the genetics of the wild stock would be adversely affected. But I think that if it is carefully managed, genetic diversity can still be maintained. Check out this article for more information.

Aquaculture
Volume 357, Number 3 (August 2012)
Interbreeding of genetically distinct native brown trout (Salmo trutta) populations designates offspring fitness
Authors: Jens Wollebæk, Knut H. Røed, Åge Brabrand, Jan Heggenes
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Source: Aquaculture, Volume 357, Number 3 (August 2012)
Page Numbers: 158 – 168
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Abstract: Supportive breeding with subsequent stocking is an important long-term conservation tool for sustaining harvestable populations and genetic diversity in wild fish populations. In salmonids, this strategy often implies, inadvertently or for logistic reasons, breeding of a mixture of local populations, which may lead to loss of local adaptation and pose risks to receiving populations. In an alpine lake system in Norway (Pålsbu-Tunhovd), we assessed long-term effects of interbreeding three brown trout (Salmo trutta) populations from separate and environmentally contrasting spawning and recruitment habitats. Using a Bayesian genetic assignment algorithm we compared numeric contributions and genetic and demographic characteristics of wild-born and lake-stocked fish within and across populations. Population contribution by the broodstock was disproportional to the number of surviving and reproductively ready stocked brown trout, indicating higher lifetime survival for brown trout descending from a large river dominated by large fish. Life history selection was further indicated by a discrepancy between observed and expected numbers of adult hybrids, i.e., fewer hybrids suggest negative fitness effects of hybridization. Hence, supportive breeding changed gene frequencies, although reduced genetic variation was not documented in mature stocked brown trout. Post stocking, these fish retained the initial length advantage relative to the fastest-growing wild-born population until the age of ten. Stocked brown trout had similar growth rates regardless of genetic origin, whereas wild-born brown trout growth rates differed among recruitment habitats. Our study in this system indicates that genetic origin determined longevity. Genetics may be a less important determinant for growth rates in lake-stocked than in wild-born brown trout.
Citation: Jens Wollebæk, Knut H. Røed, Åge Brabrand, Jan Heggenes . Interbreeding of genetically distinct native brown trout (Salmo trutta) populations designates offspring fitness. Aquaculture, Volume 357, Number 3 (August 2012), pp. 158-168, <http://ejournals.ebsco.com/direct.asp?ArticleID=4178B5BD05DA1236D955&gt;
URL: http://ejournals.ebsco.com/direct.asp?ArticleID=4178B5BD05DA1236D955

What caused the oyster mortality event on Tasmania’s East Coast in 2004?

I suspect that the oyster mortality event on Tasmania’s East Coast in 2004 is due to low DO and hyposalinity.

Aquaculture
Volume 357, Number 3 (August 2012)
Immune parameter changes of hemocytes in green-lipped mussel Perna viridisexposure to hypoxia and hyposalinity
Authors: Youji Wang, Menghong Hu, S.G. Cheung, P.K.S. Shin, Weiqun Lu, Jiale Li
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no affiliations available
Source: Aquaculture, Volume 357, Number 3 (August 2012)
Page Numbers: 22 – 29
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Abstract: Marine hypoxia owing to nutrient enrichment of water bodies by anthropogenic activities has become a global problem for several decades. Another marine environmental factor, salinity, plays an important role for marine organisms and fluctuates greatly in estuarine and coastal ecosystem, where hypoxia frequently occurs. The present study evaluated the interactive effects of hypoxia and salinity on immune functions of hemocytes in the green-lipped mussel Perna viridis, which widely distributes in estuarine and coastal waters of the Indo-Pacific region. Mussels were subjected to six combinations of oxygen levels (hypoxia: 1.5mg O2l-1, normoxia: 6.0mg O2l-1) and salinities (15‰, 22‰ and 30‰) for 168h. Mussel hemocytes were sampled after 24h, 48h, 96h and 168h exposure, for analysis of immune functions including hemocyte mortality, phagocytosis, esterase, reactive oxygen species (ROS) production, lysosomal content and total hemocyte counts using flow cytometric methods. Thereafter, all treatments were recovered to normoxic condition (6.0mg O2l-1) and salinity 30‰ for 24h to study the recovery of immune functions from the combined hypoxic and hyposaline stresses. Interactive effects of dissolved oxygen (DO) and salinity on all immune parameters were observed during the experiment. Generally, hemocyte mortality was higher at low salinity than that at high salinity levels; higher hemocyte mortality was also noted when mussels were exposed to hypoxia compared with normoxia. Phagocytosis at low salinities and hypoxia was decreased compared to normal DO and salinity treatment, respectively. The activity of esterase and ROS production at low salinity and hypoxia were reduced, respectively. Lysosomal content and total hemocyte counts were lower at low salinity and hypoxia compared to other treatments, respectively. After 24h recovery, hypoxia and salinity effects were still significant among previous treatments, indicating immune functions of P. viridiscould not recover from combined stresses in a short time.
Citation: Youji Wang, Menghong Hu, S.G. Cheung, P.K.S. Shin, Weiqun Lu, Jiale Li . Immune parameter changes of hemocytes in green-lipped mussel Perna viridisexposure to hypoxia and hyposalinity. Aquaculture, Volume 357, Number 3 (August 2012), pp. 22-29, <http://ejournals.ebsco.com/direct.asp?ArticleID=4C8FB8F8CD619D88FE81>
URL: http://ejournals.ebsco.com/direct.asp?ArticleID=4C8FB8F8CD619D88FE81

Small turtles pose a particularly high salmonella risk.

In the United States, selling turtles with a carapace less than 4 inches in length has been banned by the US Food and Drug Administration (FDA) since 1975. Despite the FDA’s ban, small turtles continue to be sold in areas that are difficult to regulate, including stores, flea markets, and fairs, and from roadside or street vendors.

Australia has done quite the opposite, brining in laws to allow the sale of small turtles!

Not only is it poor welfare for the little turtles, but also, it is not a such a good idea as we learn of such lessons in the US about the increased zoonotic risks.

Read more below:

From: “Dr. David Scarfe” ;
Date: 30 June 2012 22:55:48 AWST
Subject: AquaVetMed: CDC Warnings on Salmonella from Pet Turtles

CDC issues new warning about salmonella from pet turtles
June 30, 2012

Atlanta, GA, USA –The Centers for Disease Control and Prevention and the Pennsylvania Health Department are investing an outbreak of salmonella associated with exposure to small pet turtles. Small turtles are illegal, but they are still available from many less-reputable dealers. Sale of turtles with carapaces smaller than four inches has been prohibited in the U.S. since 1975 due to their risk of transmitting salmonella, but the CDC says “they are still available for illegal purchase through transient vendors on the street, at flea markets, and at fairs.”

This black-market wildlife trade has resulted in 132 reported cases of human salmonella infections across 18 states between August 2010 and September 2011. More than 60 percent of those cases were in children younger than 10. Of the 56 patients interviewed, 36 reported that they had been exposed to turtles. Fourteen of those patients identified “turtles too small to be legally traded,” the CDC reported in its Morbidity and Mortality Weekly Report.

Further investigation found that the water in turtle tanks in the patients’ homes tested positive for this particular strain of salmonella. As a result of this new outbreak, the CDC is warning that “turtles are not appropriate pets in households with young children or other high risk individuals,” such as pregnant women, the elderly and people with weak immune systems.

According to the report, small turtles pose a particularly high salmonella risk because they are tiny enough for children to place them in their mouths and handle them like toys. This is just the most recent outbreak of salmonella carried by small turtles. An outbreak in 2007 infected 44 people in five states. A 3-week-old baby girl in Florida died in March 2007 after being exposed to her family’s pet turtle.

The U.S. Food and Drug Administration also cautions against owning pet turtles, warning that salmonella can cause “diarrhea, fever, stomach pain, nausea, vomiting and headache.”

The CDC offers several tips for reducing the risk of turtle-associated salmonellosis, including thoroughly washing hands and any surfaces that turtles come into contact with. The agency recommends handling all turtles as if they could be contaminated with salmonella and warns that a negative salmonella test does not mean a turtle is not infected, as they do not “shed” the bacteria consistently.

As a result of this latest outbreak, the CDC says that increased enforcement against the sale of small turtles and increasing existing penalties could help decrease the likelihood of future infections.

For more CDC information and advice on Reptiles, Amphibians, and Salmonella go to http://www.cdc.gov/Features/SalmonellaFrogTurtle.

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Aquaculture gains top level recognition as a contributor to future food production.

Kofi Annan left a deep impression on world aquaculture leaders when spoke this morning, June 12 2012, on how aquaculture can contribute to feeding nine billion people by 2050.

Read more…

The Fish Vet is back.

After a month of intensive study at the Aquavet II course and visiting multiple public aquaria in western USA, Dr Loh is back with loads more knowledge and experience. Topics covered included cultured, display and laboratory:- molluscs, crustacea, finfish, elasmobranchs, corals and more. Check out The Fish Vet’s Facebook fanpage to see all the pictures taken during the recent trip.

Now that things are back to normal, consultations are now available.

Bacteriology 101 – cute video.

Check out this cute short clip on bacterial diseases in aquatic systems, how it arises and how we can fight it.

How and why collect blood in aquatic creatures?

Running blood tests that can generate information on the health of the animals including states of inflammation (e.g. bacterial infection), viral infection, their immunocompetence and more.

I believe there would be great value in aquaculture farms adopting this tool on a weekly basis as part of their normal routine. Traditional histopathology and bacteriology testing takes 4-7 days at the earliest to produce a result. Although haematology should not replace the traditional diagnostic testing, the single day turnaround time for results would allow the health advisors to check on the status of the fish health and to be able to quickly detect early signs of diseased states which will be amenable for early intervention. Because, “To be fore-warned, is to be fore-armed”.

Check out some pictures demonstrating sites for bloood/haemolymph collection here.

Following blood collection, check out this link for the best way to prepare a blood films.

Every fish farm should be routinely sampling and examining blood.