Substrate associated recruitment of juvenile Sebastes in artificial reef and natural habitats in Puget Sound and the San Juan Archipelago, Washington

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Substrate associated recruitment of juvenile Sebastes in artificial reef and natural habitats in Puget Sound and the San Juan Archipelago, Washington

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Title: Substrate associated recruitment of juvenile Sebastes in artificial reef and natural habitats in Puget Sound and the San Juan Archipelago, Washington
Author: Buckley, Raymond M
Abstract: Habitat pathways and temporal and spatial parameters of substrate associated recruitment have never been reported for juvenile quillback rockfish (S. maliger) in any ecosystem, and have never been described for juvenile copper (S. caurinus) and splitnose (S. diploproa) rockfish in Washington waters. In 1991-1994, juvenile quillback rockfish recruited only during July-August each cohort-year, correcting biannual recruitment errors in the literature for Puget Sound; first recruitment was apparently to offshore benthic habitats, with subsequent migrations to nearshore benthic macrophytes. Copper rockfish recruited during July-September each cohort-year; first recruitment was to surface and shallow water macrophytes attached to benthic substrates, with subsequent migrations to benthic macrophytes. During November-January, juvenile quillback and copper rockfish in natural macrophyte habitats migrated offshore associated with benthic drift macrophytes; juveniles in artificial and natural reef habitats migrated to deeper water associated with crevices in the substrates. Juvenile splitnose rockfish recruited during June-August each cohort-year; first recruitment was to surface drift macrophyte and seagrass habitats, which were vacated by December. Apparently co-occurring pelagic juvenile copper and splitnose rockfish selectively recruited to attached and detached vegetation habitats, respectively.Development of internal micro-tagging procedures for juvenile Sebastes enabled the first estimation of instantaneous natural loss rate (mortality and emigration) for this genus, without non-immigration assumptions. The estimate of Z$\sb{\rm 258d}$ = 0.0106 for juvenile quillback rockfish on an artificial reef recruitment habitat, was lower than for a coastal pelagic species, the only other estimate for juvenile Sebastes. Nearshore artificial reef substrate manipulations functioned as juvenile rockfish recruitment habitats, providing preferred nursery and refuge habitats and enhancing local recruitment. Efficacies of artificial reef recruitment habitats located adjacent to, and isolated from, established artificial reefs, were affected by variability in levels of juvenile rockfish recruitment, biogenic habitat parameters, and ecological maturity of the substrates. Micro-tagged juvenile rockfishes remained on artificial reef recruitment habitats during the cohort-year, contrasting emigrations from natural macrophyte habitats. Increased densities of juvenile rockfish on artificial reef recruitment habitats late in the cohort-year indicated emigrations from natural habitats. Juvenile rockfish had average daily growth rates of 0.11-0.13 mm total length in both natural and artificial reef recruitment habitats.
Description: Thesis (Ph. D.)--University of Washington, 1997
URI: http://hdl.handle.net/1773/5373

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