POPULATION GENETICS OF Apostichopus californicus ALONG THE PACIFIC COAST OF NORTH AMERICA

Commercial aquaculture production methods for the California sea cucumber (Apostichopus californicus) are being developed in response to high demand in overseas markets and wild stock declines. Because interbreeding of wild and farmed animals can lead to genetic risks, patterns in population structure in the wild is important to inform aquaculture practices, such as the site choice for collection of broodstock and transfer of seed across geographic areas. Here, we quantify population structure (1) at a small-scale, within Puget Sound, and (2) at a broad-scale, from Alaska to California. We used single-digest restriction site associated DNA (RAD) sequencing, the dDocent software package, and custom filtering scripts to identify 1680 single nucleotide polymorphisms (SNPs) across nine collection sites of A. apostichopus. Using these SNPs, we estimated population structure to be significant yet low, consistent with previous results. Additionally, we found strong evidence for isolation by distance, suggesting that dispersal is geographically limited and drives population differentiation. We detected population structure at both small and large geographic scales; even within Puget sound, the majority of pairwise population comparisons were significantly differentiated. We recommend that these estimates of population differentiation be considered in management decisions concerning movement of broodstock and seed, to limit artificial gene flow among differentiated populations.