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Creator:: Gallagher, Charmaine Marie, Sylvia, Gil, and Hannah, Robert W.
Abstract:: Oregon ocean shrimp annual harvest relies on the successful recruitment and growth of age one shrimp. Changes in oceanic conditions appear to have major impacts on recruitment, spatial abundance and growth rates. Successful recruitment has been identified with the timing and strength of the spring transition generating oceanic conditions favorable...
Resource Type:: Research Paper

Creator:: Charnov, Eric L. and Hannah, Robert W.
Abstract:: Long-term data sets that quantitatively confirm basic ecological theory are rare for field populations. Highly variable recruitment often causes wide temporal variation in population age distribution and basic theory for adaptive sex ratio often predicts ‘sex ratio tracking’ to match the fluctuating age distribution. Using sex-changing shrimp as a model...
Resource Type:: Article

Creator:: Krutzikowsky, Vicki Hoover, Hannah, Robert W., Sylvia, Gilbert, and Morrissey, Michael
Abstract:: We hypothesized that bycatch may affect the quality of the shrimp by causing breakage. A double-rigged commercial shrimp vessel was chartered for test fishing. One net employed a Nordmore grate BRD and the other served as a control. Bycatch was measured from each net. The shrimp catch was kept separate...
Resource Type:: Presentation

Creator:: Hannah, Robert W. and Matteson, Keith M.
Abstract:: We evaluated the effect of barotrauma on the behavior of nine species of Pacific rockfish Sebastes spp. after hook-and-line capture and release using a video-equipped underwater release cage. Sampling was conducted across a range of bottom depths (12-194 m), mostly where barotrauma resulting from an expanded swim bladder and gaseous...
Resource Type:: Article

Creator:: Hannah, Robert W.
Abstract:: Changes in the spatial distribution of U.S. west coast bottom-trawl effort in relation to areas of prime habitat for rockfish Sebastes spp. were evaluated between 1992 and 2001. Prime trawlable rockfish habitat (PTRH) was defined based on the spatial distribution of high rockfish catches from logbook data for 1992–1995. Bottom-trawl...
Resource Type:: Article

Creator:: Parker, Steven J., McElderry, Howard I., Rankin, Polly S., and Hannah, Robert W.
Abstract:: Fishes with closed swim bladders regulate buoyancy during depth changes by secreting and resorbing swim bladder gases. Forced ascent during fishery capture results in barotrauma caused by rapid expansion and exsolution of gases from body fluids. Pressure changes in hyperbaric chambers were used to examine changes in swim bladder integrity...
Resource Type:: Article

Creator:: Parker, Steven J., Rankin, Polly S., Hannah, Robert W., and Schreck, Carl B.
Abstract:: The lingcod Ophiodon elongatus is a benthic marine fish commonly caught by groundfish trawlers and discarded due to low catch limits. Managers must account for the mortality of bycatch to assess population status accurately. Our objectives were to estimate the actual mortality of trawl-discarded lingcod (50- 84 cm) and describe...
Resource Type:: Article

Creator:: Hannah, Robert W., Parker, Steven J., and Matteson, Keith M.
Abstract:: We evaluated the effect of capture depth and fish size on the ability of several Pacific rockfishes Sebastes spp. to resubmerge after hook-and-line capture and surface release. We observed fish as they were released into a bottomless floating enclosure, and we recorded submergence success within a 5-min time limit. Submergence...
Resource Type:: Article

Creator:: Hannah, Robert W., Parker, Steven J., and Buell, Troy V.
Abstract:: We tested the potential of a selective flatfish trawl to reduce bycatch of slope rockfish in the upper continental slope bottom-trawl fishery (250–500 m) on the U.S. West Coast. The trawl we tested differed from typical slope trawls in that it was a low-rise, two-seam trawl with a severely cut...
Resource Type:: Article

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