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Inbreeding and disease in tropical shrimp aquaculture: a reappraisal and caution

Inbreeding and disease in tropical shrimp aquaculture: a reappraisal and caution | Aquaculture Directory | Scoop.it

NACA recommends that anyone involved in shrimp aquaculture - particularly hatcheries but also anyone procuring PL - read a paper by Roger Doyle, recently published in Aquaculture Research which discusses the link between inbreeding and disease in tropical shrimp aquaculture:

 

"The disease crisis facing shrimp aquaculture may be propelled, in part, by an interaction between management practices that cause inbreeding, and the amplification by inbreeding of susceptibility to disease and environmental stresses. The study describes and numerically simulates gene flow from Penaeus (Litopenaeus) vannamei hatcheries that employ a ‘Breeder Lock’ to discourage use of their PL as breeders, through ‘copy hatcheries’ that breed the locked PL, to inbred shrimp in farm ponds. Re-analysis of published data shows that inbreeding depression under stress is exceptionally strong in shrimp. Inbreeding is currently overlooked as a problem because: (1) procedures recommended for well-managed hatcheries do not consider their implications for the copy hatcheries that supply most farmed shrimp (estimated 70%), (2) inbreeding in hatcheries is often reported as zero even though zero is the mathematical expectation of the usual estimator (Fis, fixation index) whatever the true genealogy of the broodstock. Simulation shows, however, that inbreeding can be estimated with Wang's trioML estimator, that Fis can differentiate Breeder Locked from copy PL and that simple tests can verify the lock status of PL. The importance of inbreeding should be re-evaluated in the context of disease and environmental stress. Unrecognized inbreeding may increase the incidence, prevalence and lethality of WSSV, IHHNV, EMS (AHPND) and other diseases."

 

DOI: 10.1111/are.12472


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John Bostock's curator insight, May 24, 1:39 AM

Interesting and challenging paper.

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Triploid and diploid Atlantic salmon show similar susceptibility to infection with salmon lice Lepeophtheirus salmonis - Frenzl - Pest Management Science - Wiley Online Library

Triploid and diploid Atlantic salmon show similar susceptibility to infection with salmon lice Lepeophtheirus salmonis - Frenzl - Pest Management Science - Wiley Online Library | Aquaculture Directory | Scoop.it

Sea lice infection is the most expensive disease factor for Atlantic salmon sea-cage farming. For triploid salmon to be accepted as a commercial possibility, investigation of susceptibility of triploid salmon to sea lice infection is a fundamental milestone. The susceptibility of diploid and triploid salmon to infection with Lepeophtheirus salmonis was examined in a tank trial in Scotland, a tank trial in Norway and a cage trial in Scotland.Results

Following a single infection challenge, results indicated a significant correlation between fish size and the number of attached sea lice. Triploid fish were larger than diploids at the smolt stage. In the tank trials, no difference was found between infection levels on diploids and triploids after a single infection challenge. The tank trial in Scotland continued with a second infection challenge of the same fish, which also showed no infection differences between ploidies. A borderline correlation between first infection and re-infection intensity was found for PIT-tagged diploid salmon examined after each challenge. No significant difference in louse infection between diploid and triploid salmon (~2 kg) was found in the cage trial undertaken under commercial conditions.

Conclusion

This study concludes that triploid Atlantic salmon are not more susceptible to sea louse infection than diploid fish.


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