Graduate Thesis Or Dissertation
 

How Nearshore Currents affect Larval Dispersal and Genetic Connectivity of China Rockfish (Sebastes nebulosus) Along Oregon and Washington Coasts

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/mk61rr20c

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  • Connectivity of fish populations is a crucial question for fisheries conservation and the development of spatial management plans. Both adult and larval movement define the extent and direction of ecological and evolutionary overlap between geographic regions and, therefore, how we define stocks for management purposes. Within that context, my work focuses on the dispersal of a nearshore, demersal species, the China Rockfish (Sebastes nebulosus), which supports an economically important Northeast Pacific nearshore groundfish fishery. Our aim was to determine how larval transport affects genetic diversity and connectivity along the Oregon and Washington coasts. For the genetic analyses, we used restriction site-associated DNA sequencing (RADseq), known as 2b-RAD, to investigate population structure. Fin clip samples were collected along the Oregon and Washington coasts. A total of 2,199 single nucleotide polymorphisms (SNPs) were identified from 255 individuals. We found that there is no population structure among populations in the Oregon and Washington coast. Pairwise FST (<0.05), comparatively among localities, and average FST results indicate that populations in Oregon and Washington have high levels of connectivity and should be considered as one population for management considerations. All the genetic diversity came from within individuals, not among populations. Overall results from oceanographic ROMs modeling indicate seasonal variability in levels of connectivity. Model results indicate that during 2009-2018, particles released in Southern Oregon, as far south as Port Orford in Oregon, Northern Oregon, and as far north as the Olympic Coast National Marine Sanctuary (OCNMS) in Washington area are all at one point or another, connected. Highest connectivity from the southern end of the modeled region (southern and northern Oregon sites) to the northern site occurred during the northward flow of currents in the winter. Highest connectivity from the northern half (Washington and northern Oregon) to the southern sites occurred after the spring transition. Nevertheless, these results suggest that nearshore oceanographic currents could be useful for identifying patterns of genetic connectivity among species with similar life history to that of the China Rockfish. Since China Rockfish are nearshore dwellers and have a very limited adult home range, we expected to find low genetic diversity at a localized level (i.e., within a specific area like a marine reserve or MPA); and high genetic connectivity across the entire two-state study area, suggesting that larvae are mostly dispersed by nearshores ocean currents. These results are consistent with what we know of marine populations that have low FST values and indicates little genetic differentiation, i.e., high level of genetic connectivity, and confirm that the combination of genetic techniques with oceanographic modeling can help inform stock boundaries and fisheries management in a low FST marine species. Overall, there is connectivity among the three sites examined (genetically and oceanographically). In terms of stock definition and assessments, the population of China Rockfish in Oregon and Washington would be considered one population, or one stock, since they have such high levels of connectivity, and it should be managed as one population, which is of particular importance at this point for the Pacific Fishery Management Council that is currently in the process of redefining some stocks for management purposes.
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  • Pending Publication
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  • 2023-01-06 to 2024-02-07

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