Skate egg nursery areas support genetic diversity of Alaska and Aleutian skates in the Bering Sea

Abstract

Skate egg case nursery sites are specific locations on the ocean floor where some species of skates deposit egg cases to incubate for up to 5 yr until hatching. We examined genetic diversity within and among skate egg nursery sites of the Alaska skate Bathyraja parmifera and the Aleutian skate B. aleutica in the eastern Bering Sea to gain a better understanding of how skates utilize these areas. Restriction-site associated DNA (RAD) sequencing libraries were used to obtain single nucleotide polymorphism (SNP) datasets for B. parmifera (5285 SNPs) and B. aleutica (3309 SNPs). We found evidence for significant genetic differentiation among all B. parmifera and B. aleutica nursery areas, with 1 exception. B. parmifera from the spatially proximate Pribilof and Bering Canyons were genetically similar, suggesting that this may represent a large contiguous nursery area. Genetic differences between embryos at distinct developmental stages within nursery areas were not significant. Adult B. parmifera taken from the Bering Sea and Aleutian Islands were genetically distinct from embryo collections, implying that additional genetic types of B. parmifera may exist that were not represented by the nursery areas sampled in this study. Our data also showed evidence for low effective population sizes and low Ne/N ratios. Results indicate that nursery areas support genetically distinct components of each species, which underscores the importance of skate egg nursery areas for conservation of genetic diversity.