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Oceanographic effects on the dynamics of food habits and growth condition of some groundfish species of the Pacific Northwest

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dc.contributor.advisor Sampson, David B.
dc.creator Lee, Yong Woo
dc.date.accessioned 2007-12-10T15:45:02Z
dc.date.available 2007-12-10T15:45:02Z
dc.date.copyright 2002-07-29
dc.date.issued 2002-07-29
dc.identifier.uri http://hdl.handle.net/1957/7315
dc.description Graduation date: 2003
dc.description.abstract Marine fish are subject to direct and indirect oceanographic variations operating at short and long time scales. In this study feeding habits and long-term growth condition of several groundfish species of the Pacific Northwest are examined to understand the relationship between variations in the fish's biological and life history components and the ocean environment. Stomach samples of three rockfish species, yellowtail rockfish (Sebastes flavidus), widow rockfish (S. entomelas), and canary rockfish (S. pinniger), which were collected seasonally off the Pacific Northwest in 1998 and 1999, provided quantitative information on the food habits of the species during and directly after the 1997-98 El Nino event. The diets of these co-occurring species were markedly different from each other. Unusual southern zooplankton species were found in the diets of all three species possibly due to the influence of the El Niflo event. The diet of S. flavidus in 1998 summer (El Nino) was contrasted with results from a previous study based on 1980 summer samples (non-El Nino), and found to be different. An assessment of long-term changes in fish growth condition was conducted using data from Oregon market samples, in which the fish weights are generally measured for aggregations of fish rather than individuals. Non-linear regression can be applied to this type of data to estimate the length-weight parameters and to detect long-term changes in growth condition. The reliability of the estimation method was tested using Monte Carlo simulation. The results demonstrate that the estimation method provides reasonably accurate estimates and is sufficiently powerful to detect small changes in the length-weight relationship. Using Oregon market sample data collected over several decades and the non-linear regression method, growth condition indices were developed and examined for five fish species: Dover sole (Microstomus pacificus), petrale sole (Eopsetta jordani), canary rockfish, yellowtail rockfish, and widow rockfish. No particular trend or close association with environmental variables was evident in the long-term growth condition indices for any of the species, but interannual and seasonal variations in condition were clearly evident. Possible reasons for the lack of long-term trends in condition and the lack of any close association with the environmental variables are discussed. en
dc.format.extent 1839796 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.subject.lcsh Fishes -- Northwest, Pacific -- Growth en
dc.subject.lcsh Sebastes -- Ecology -- Northwest, Pacific en
dc.subject.lcsh Upwelling (Oceanography) -- Northwest, Pacific en
dc.subject.lcsh El Niño Current en
dc.subject.lcsh Sebastes -- Food -- Northwest, Pacific en
dc.title Oceanographic effects on the dynamics of food habits and growth condition of some groundfish species of the Pacific Northwest en
dc.type Thesis en
dc.degree.name Doctor of Philosophy (Ph. D.) in Fisheries Science en
dc.degree.level Doctoral en
dc.degree.discipline Fisheries and Wildlife en
dc.degree.grantor Oregon State University en
dc.contributor.committeemember Lesser, Virginia
dc.contributor.committeemember Peterson, William
dc.contributor.committeemember Gregory, Stanley
dc.description.digitization Master files scanned at 600 ppi (256 Grayscale) using Capture Perfect 3.0 on a Canon DR-9080C in TIF format. PDF derivative scanned at 300 ppi (256 B&W), using Capture Perfect 3.0, on a Canon DR-9080C. CVista PdfCompressor 3.1 was used for pdf compression and textual OCR. en

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