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Newport, OR, United States

Karpov K.A.,Karpov Marine Biological Research | Law P.M.,50 Harbor Boulevard | Valle C.F.,665 Lampson Avenue | Fox D.,040 Southeast Marine Science Drive
California Fish and Game | Year: 2010

When designing a monitoring program, it is important to determine how much sampling is needed prior to data collection. Programs with too little statistical power produce ambiguous results and public debate that cannot be resolved. However, prospective power analysis requires an estimate of sample variance. In this paper, data from strip transect surveys using remote operated vehicle (ROV) of fish on temperate subtidal rocky reefs were used to establish the relationship between density and variance needed for power analysis. The relationship was used to select the optimal sample unit (transect) size and estimate the total sampling effort needed to measure specific changes in density between two sampling study areas. In general, smaller transects were more efficient than larger transects. The smallest transects (50 m2) were most efficient, but the difference between 50-m2 transects and 100-, 200-, and 400-m2 transects was relatively small (11% to 28%). The largest transects (800 m2), however, required 57% more sampling area than 50-m2 transects. The total sampling area needed to detect a significant difference in density increased with decreasing effect size, as expected. Also as expected, some species (e.g. copper rockfish) required more sampling effort than others (e.g. vermilion rockfish). These results demonstrate that pre-existing data may be used to establish relationships between means and variances, and to determine the optimal transect size and the amount of sampling effort needed to measure statistically significant differences in fish density between study areas. Source

Pribyl A.L.,Oregon State University | Pribyl A.L.,National Oceanic and Atmospheric Administration | Kent M.L.,Oregon State University | Kent M.L.,NIWA - National Institute of Water and Atmospheric Research | And 2 more authors.
Transactions of the American Fisheries Society | Year: 2011

Pacific rockfish experience high discard mortality when captured owing to a condition called barotrauma, which is caused by the change in pressure during capture. This condition appears to be species specific at the macroscopic level; however, little is known about the microscopic tissue-level effects of barotrauma. Determining whether tissue-level injuries are also species specific or influenced by factors such as life history and phylogenetic relatedness can improve our management of discard mortality. We evaluated the responses of six species of Pacific rockfish (black rockfish Sebastes melanops, blue rockfish S. mystinus, yellowtail rockfish S. flavidus, quillback rockfish S. maliger, canary rockfish S. pinniger, and yelloweye rockfish S. ruberrimus) captured from varying depths to forced decompression at the histological level (heart ventricle, rete mirabile, head kidney, liver, gill, and eye) as well as the macroscopic level. At the macroscopic level we focused on injuries caused by barotrauma, namely, everted esophaguses, exophthalmia, ocular emphysema, and ruptured swim bladders. Yellowtail and quillback rockfish experienced the fewest macroscopic injuries. Depth of capture influenced the presence of exophthalmia in quillback rockfish and ocular emphysema in quillback and yelloweye rockfish. Tissue injuries as a result of forced decompression included emphysema in the heart ventricle, emboli in the vessels of the rete mirabile, and emboli in the vessels of the head kidney. No injuries were observed at the histological level in the liver, gill, or eye owing to barotrauma. We could not detect a difference in the tissue-level response to barotrauma among the six species, suggesting that all species are susceptible to high internal gas pressure during forced decompression. © American Fisheries Society 2011. Source

Cope J.M.,National Oceanic and Atmospheric Administration | Devore J.,Pacific Fishery Management Council | Dick E.J.,Southwest Fisheries Science Center | Ames K.,Pacific Fishery Management Council | And 7 more authors.
North American Journal of Fisheries Management | Year: 2011

The Magnuson-Stevens Fishery Conservation and Management Act (MSA) requires active management of all stocks at risk of overfishing or otherwise in need of conservation andmanagement. In the Pacific Fishery Management Council groundfish fishery management plan, about two-thirds of the more than 90 managed stocks are currently without traditional assessments to help define stock status in relation to management targets. Stock complexes are often employed for management purposes in such situations. The guidelines issued in respons to the 2006 MSA amendments defined a complex as a group of stocks with similar geographic distributions, life histories, and vulnerabilities to fisheries. This work uses productivity-susceptibility analysis (PSA) to measure the vulnerabilities of 90 managed groundfish stocks, 64 of which are currently managed within stock complexes. These stock complexes are reevaluated by first using a partitioning cluster analysis to group the stocks by depth and latitude. Vulnerability reference points are then established based on the PSA results to determine vulnerability groups of low, medium, high, and major concern within each ecological group. This method is a simple and flexible approach to incorporating vulnerability measures into stock complex designations while providing information with which to prioritize stockand complex-specific management. © American Fisheries Society 2011. Source

Johnson S.L.,040 Southeast Marine Science Drive | Power J.H.,U.S. Environmental Protection Agency | Wilson D.R.,040 Southeast Marine Science Drive | Ray J.,040 Southeast Marine Science Drive
North American Journal of Fisheries Management | Year: 2010

We tracked three groups of steelhead Oncorhynchus mykiss smolts implanted with acoustic transmitters to determine whether the degree of hatchery domestication or the juvenile rearing environment (hatchery raceway versus natural stream) influenced migration timing and survival in the Alsea River and estuary, Oregon. Two groups consisted of age-1 smolts reared in concrete raceways. One hatchery-reared group (traditional brood group) was derived from the traditional Alsea River broodstock initially developed in the 1950s. The second hatchery-reared group (new brood group) was derived from naturally reared Alsea River adult steelhead that were captured and spawned at the hatchery beginning in the winter of 2000-2001. The third group (naturally reared group) consisted of age-2 naturally reared smolts captured in a downstream migrant trap located in a tributary stream near the hatchery. We placed transmitters in 74 traditional brood smolts, 76 new brood smolts, and 72 naturally reared smolts. Thirty-one acoustic receivers were located throughout the Alsea River and estuary and in the ocean offshore of the river mouth to monitor smolt movement. We found no significant difference between groups in their survival to the head of tide or to the mouth of the estuary. Most smolts from all three groups were detected at the head of tide (87% of fish from the traditional brood group, 78% from the new brood group, and 84% from the naturally reared group). However, survival was poor in the lower estuary for all three groups; we estimated that only 37% of the traditional brood group, 45% of the new brood group, and 47% of the naturally reared group survived to the ocean. The timing of migration through the river was highly variable in all three groups, and we found no significant differences in the rate of downstream movement from the release site to the head of tide. Mean residence time within the estuary was similar for all groups, although smolts from the naturally reared group showed less variability in estuary residence time than hatchery-reared smolts. © Copyright by the American Fisheries Society. Source

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