Genetics of Shellfish on a Human‐Dominated Planet

The ecology, evolution, impacts and management of host–parasite interactions of marine molluscs

“…This may result in inbreeding depression, which lowers survivorship and fitness of the inbred individuals (e.g., Bierne et al, 1998;Launey and Hedgecock, 2001) and may diminish the genetic 'health' of wild populations if the selectively bred and wild oyster populations interbreed (Wang and Ryman, 2001). Further although the selectively bred line(s) may exhibit superior performance when exposed to a particular parasite for which resistance has been selectively bred, genotype by environment interactions may result in this line being sub-optimal under alternative 'environmental' or 'biological' conditions (e.g., Mallet and Haley, 1983;Rawson and Hilbish, 1991;Camara and Vadopalas, 2009;Hedgecock, 2011;Degremont et al, in press this volume). For example, Sydney rock oysters selectively bred for disease resistance appear to be less resilient to enhanced pCO 2 than wild oysters (Thompson et al, 2015).…”

“…Selective breeding programs, often aimed at accelerating growth or enhancing resistance to particular diseases, can result in reduced genetic variation among cultivated as compared to wild molluscan populations and in some instances may result in inbreeding depression (e.g., Bower, 1992;Evans et al, 2004;NRC, 2004a;Gaffney, 2006;Hare et al, 2006;Camara and Vadopalas, 2009;Hoffman et al, 2009;Hedgecock, 2011;Rohfritsch et al, 2013; in press also in this volume). This may render cultivated populations more susceptible to diseases for which they have not been selectively bred for resistance against.…”

“…As more molluscs are cultured across the globe, potentially without good genetic practices (inbreeding, small brood stock numbers), populations of wild molluscs, especially those that have significantly depressed population sizes, such as Ostrea lurida and O. edulis, may be affected by interbreeding with captively-bred populations that may lack local adaptations and genetic variability to respond to existing, let alone novel introduced diseases and parasites (discussed related Sections here, and in Gaffney, 2006;Camara and Vadopalas, 2009;Hedgecock, 2011; in press this volume).…”

“…As disease epidemics have threatened the viability of molluscan aquaculture industries, they have increasingly turned to cultivation of animals selectively bred for disease resistance and rapid growth (e.g., Ragone Calvo et al, 2003;Dove et al, 2013;Degremont et al, in press this volume). Selective breeding programs in many instances take advantage of natural variation in the susceptibility of individuals to disease, and the heritability of this trait (discussed in Elston and Ford, 2011;Hedgecock, 2011;Camara and Vadopalas, 2009).…”

Sustainable large‐scale production of European flat oyster (Ostrea edulis) seed for ecological restoration and aquaculture: a review

“…Triploid oysters may increase (in some cases and species) the growth rate (Guo et al . 1996), may allow the protection of the hatchery product and may decrease the genetic impact of hatched oysters and natural populations (Hedgecock 2011). However, differences in survival rates between diploids and triploids are not clear due to interactions with diseases or other stressors and the difference of ploidy level for each situation and oyster species (Nell 2002).…”