Publication Date

Summer 2024

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Richard Starr; Scott Hamilton; BirgitteMcDonald

Abstract

Rockfishes (Sebastes spp.) are ecologically and economically important fishes in the continental shelf and slope regions of the Eastern Pacific Ocean. All species within the Sebastes genus have a buoyancy organ, the swim bladder, which is sensitive to rapid changes in pressure that occur when fish are caught and brought up to the surface. Although all rockfishes have swim bladders, pressure-related injuries (barotrauma) affect rockfish species differently. I determined whether swim bladder morphology can explain differences in barotrauma among semi-pelagic (Blue and Olive rockfish) and benthic (Gopher and Vermilion rockfish) species that occupy different habitat zones. Seven different swim bladder morphological features were quantified and related to external barotrauma injuries observed upon capture. Benthic Vermilion rockfish displayed a greater incidence of barotraumatic injuries and had thicker swim bladder membranes with a higher tearing threshold than the semi-pelagic species. Conversely, the swim bladders of Blue rockfish were significantly thinner and more elastic, and experienced fewer barotraumatic injuries, than both benthic species. Despite responding differently to barotrauma, many swim bladder measurements were similar between Olive and Gopher rockfish. The number and severity of barotraumatic injuries decreased with increasing body size in Blue rockfish, consistent with a significant increase in tearing threshold and membrane thickness with total length. This research furthers the understanding of pressure-related injuries among rockfish species, while informing fishery managers about the impacts of swim bladder morphology on discard mortality rates.

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