Bivalve Life History and Genetics
Dennis Hedgecock (panel moderator), University of Southern California
Abstract
Use of nonnative species, reductions in biodiversity, and gene flow between domesticated farmed and wild stocks are potential genetic impacts of bivalve aquaculture. Although most shellfish culture in the Pacific Northwest is based on naturalized, nonnative species (the native geoduck being the notable exception), there are currently strict regulations on international and interstate transport of shellfish. As the aquaculture industry is not currently a vector of introductions, little or no research is needed on this issue. On the other hand, interactions of wild and farmed shellfish stocks deserve greater attention and research support. Aquaculture in general, and bivalve culture in particular, lack domesticated strains and rely on hatchery propagation of wild stocks. The legendary high fecundity of bivalve mollusc females can typically spawn tens of millions of eggs at one time, which creates a risk that hatchery-propagated shellfish stocks could dilute the genetic diversity of wild populations and possibly elevate the frequencies of harmful mutations. Continued farming of wild, native species will raise rather than lower these risks over time. Moreover, farming wild animals is a less efficient food production system than one based on domesticated stocks, which make possible improved traits, increased production efficiency, and reduced environmental and energy footprints. Yet, use of genetically divergent domesticated stock might also increase risk of detrimental effects on the genetics of wild populations. Farming triploid bivalves, which are largely sterile, essentially eliminates genetic interactions with wild shellfish. However, since tetraploid bivalves are used to generate triploid seed and tetraploids are self-fertile, the bio-security of tetraploid stocks becomes a new issue for study. Research on developing and improving domesticated shellfish for aquaculture and on improved methods for eliminating interaction with wild populations (bio-security) should have high priority for research leading to sustainable management of shellfish resources.