Geoduck Genetics: What We Know, What We Don’t Know, and Why It Matters
Brent Vadopalas, School of Aquatic and Fishery Sciences, University of Washington
Abstract
Neutral population genetic analyses can be powerful tools for understanding the genetic connectivity among groups of organisms. There have been two investigations of genetic connectivity in geoduck clams. The first project used two types of genetic markers to look at genetic connectivity at different spatial scales primarily within Puget Sound. The second study expanded the spatial scale to include the Queen Charlotte Islands (QCI), SE Alaska (AK), Vancouver Island (VI), and Puget Sound (PS). A primary finding in both studies was the presence of extremely high genetic variability within aggregations of wild geoduck, with genetic structure only at the broadest spatial scale (QCI, AK, VI, and PS). For geoduck aquaculture in PS, a primary genetic issue is whether the high genetic variability observed in wild populations is at risk of being reduced by cultured geoduck. Such changes might occur if cultured geoduck mature and spawn during the course of the culture cycle, and if cultured and wild geoduck are genetically distinct. The first question was addressed by examining 1-5 year old cultured geoduck for evidence of maturation and spawning (gamete release) from three PS farms. The majority of 2- to 5-year-old geoduck spawned during March, April, and May, in concert with their wild counterparts. To assess genetic risk, it remains important to determine whether cultured geoduck are genetically distinct from wild populations. Seven key life-history traits — adult viability, fecundity (number of gametes), fertility (capacity to reproduce), age at maturation, reproductive success, juvenile survival/viability, and larval dispersal patterns — can influence genetic risk to wild geoduck. Should genetic risk be realized based on genetic differentiation of cultured and wild geoduck combined with these seven traits, some form of maturation control may mitigate genetic risks associated with geoduck aquaculture.