Abstract
Little is known about intraspecific variation within the deacon rockfish (Sebastes diaconus), a recently described species found in the northeast Pacific Ocean. We investigated population structure among fish sampled from two nearshore reefs (Siletz Reef and Seal Rock) and one offshore site (Stonewall Bank) within a <50‐km2 area off the Oregon coast. Fish from the three sample sites exhibited small but statistically significant differences based on genetic variation at >15,000 neutral loci, whether analyzed independently or classified into nearshore and offshore groups. Male and females were readily distinguished using genetic data and 92 outlier loci were associated with sex, potentially indicating differential selection between males and females. Morphometric results indicated that there was significant secondary sexual dimorphism in otolith shape, but further sampling is required to disentangle potential confounding influence of age. This study is the first step toward understanding intraspecific variation within the deacon rockfish and the potential management implications. Since differentiation among the three sample sites was small, we consider the results to be suggestive of a single stock. However, future studies should evaluate how the stock is affected by differences in sex, age, and gene flow between the nearshore and offshore environments.
Highlights
A high diversity of Sebastes rockfish occur in the northeast Pacific Ocean (Hyde & Vetter, 2007; Love, Yoklavich, & Thorsteinson, 2002)
Sex was again recorded, but the first two principal components (PCs) reflected obvious geographic structure among sampling re‐ gions (Andrews et al, 2018). Comparison of these findings suggests that the genetic difference estimated between male and female deacon rockfish is relatively strong within the Sebastes genus, but the potential cause is unknown until further biological information is available for the species
We found small but statistically significant otolith shape and ge‐ netic differences among deacon rockfish sampled off the Oregon coast, regardless of whether the three sample sites were analyzed independently or organized into nearshore and offshore groups
Summary
A high diversity of Sebastes rockfish occur in the northeast Pacific Ocean (Hyde & Vetter, 2007; Love, Yoklavich, & Thorsteinson, 2002). In Oregon, semipelagic nearshore rockfish are the primary target of the recreational fleet and these fisheries represent a vital economic component of coastal communities (Research Group, 2015a, 2015b) Despite their economic importance, our understanding of the basic biol‐ ogy of these semipelagic species is lacking, which in turn affects our ability to conduct accurate stock assessments (Dick et al, 2017). The need to precisely define stock boundaries in the management of rockfish was demonstrated by a recent population genetic study of three species sampled from Puget Sound and outer coastal waters (Andrews et al, 2018). The aim of this study was to use an interdisciplinary approach (Abaunza et al, 2013) to test for population structure and potential fish stocks among deacon rockfish off the Oregon coast based on otolith shape and genetic variation. To disentangle any potential interaction between sample location and sex, we analyzed genetic variation among the three sample sites using males and females separately
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