Graduate Thesis Or Dissertation

 

A critical examination of the ageing method for sablefish (Anoplopoma fimbria) from the U.S. west coast using edge analysis and oxytetracycline Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/j098zd792

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  • This thesis evaluates the current break-and-burn ageing method for the southern stock (U.S. west coast) of sablefish (Anoplopoma fimbria). Differences in growth rates between the northern (north of Vancouver Island, BC) and southern stocks (south of Vancouver Island, BC) and results from a radiometric study conducted on fish from the southern stock suggest that the ageing method, developed from fish from the northern stock, may not be appropriate for fish in the southern stock. An edge analysis, using fish landed in Oregon, confirmed the formation of one hyaline zone annually. The timing of the deposition of the hyaline zone, May through September, is unique for fish from temperate waters. Sablefish tagged and injected with oxytetracycline (OTC) did not indicate ageing error significant enough to warrant the development of a new ageing method but some amendments to the current ageing method are recommended: do not excessively split marks in the transition zone (the area on the otolith that corresponds to the change from early fast growth to older slow growth); if multiple marks originate from the same spot on the ventral edge of the otolith, concentrate on the narrowing opaque zones when determining which marks to count as annuli; and assign age ranges or discard otoliths that display odd growth patterns. These amendments may increase the accuracy and precision of sablefish age estimates. Neither final age nor any of the auxiliary catch data (sex, size, depth, and latitude at recapture) contributed significantly to the ageing error. It is also recommended that the thin section method of preparing otoliths be used in future sablefish OTC studies.
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