Young-of-the-year rockfish (Sebastes spp.) settlement dynamics in Oregon estuaries Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/qf85nd73d

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  • In the Pacific Northwest, several species of rockfishes (Sebastes spp.) are under extreme conservation measures due to low population levels. Although currently at healthy population levels, one species of interest is the black rockfish (S. melanops), which has been shown to utilize estuarine habitat during its early life history stages. Black rockfish constitute a large portion of the recreational harvest in the Pacific Northwest, and are also a commercially fished species along the majority of the west coast. Annual recruitment in rockfishes has been shown to be extremely variable, and a better understanding of the factors behind successful recruitment and the subsequent settlement process would assist in prioritizing management and conservation efforts for this and other species. The overall goal of my study was to investigate the role that natural and anthropogenic influences play in the estuarine settlement dynamics of northeast Pacific rockfishes, using black rockfish as the primary study species. Genetic identifications confirmed that the majority of the young-of-the-year (YOY) rockfish captured during this study were S. melanops, with small numbers of S. caurinus and S. emphaeus present as well. Results from trapping surveys indicated that YOY black rockfish utilize multiple estuaries on the Oregon coast from spring through late fall, and may be present in highly developed estuaries through their first winter before moving to deeper habitats, as shown by late season increases in catch-per-unit-effort (CPUEs) and the capture of multiple age-1 juveniles in the estuary. Catches were higher in the more developed estuaries on the coast, suggesting that the presence of structure is an extremely important component to the settlement process in this species and that the continued development of Oregon estuaries may not adversely affect YOY rockfish settlement. Two years of dive surveys on a standardized set of artificial reef structures in Yaquina Bay showed that a settlement index of YOY rockfish within the estuary could reflect larger trends in the YOY population and suggest that habitat saturation is not a factor that affects the settlement process of YOY rockfish in estuaries. This study provides strong evidence of widespread use of estuarine habitat on the Oregon coast by black rockfish during their first year of life, and provides additional support that structure is an important component to the settlement process, and has set the groundwork for investigating inter-annual variation in the estuarine settlement of rockfish.
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