Kodiak Alaska Tanner Crab Chionoecetes Bairdi Research

Author : Kally Spalinger
Publisher :
ISBN 13 :
Total Pages : 48 pages
Book Rating : 4.:/5 (132 download)

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Download or read book Historical Abundances of Tanner Crab Chionoecetes Bairdi for Kodiak, Chignik, South Peninsula, and Eastern Aleutian Districts from Standardized Large-mesh Trawl Surveys, 1988–2021 written by Kally Spalinger and published by . This book was released on 2022 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Alaska Department of Fish and Game (ADF&G) is updating long-term average abundance indices of mature male Tanner crab Chionoecetes bairdi used to determine regulatory fishery thresholds in the Kodiak, Chignik, South Peninsula, and Eastern Aleutian Districts. Since 1988, trawl survey area-swept abundance estimates have been determined annually, using the same vessel and net configuration. Initial thresholds were established in 1999, when only 11 years of consistent trawl survey estimates were available. To provide for a longer time series, 4 different methods were used to reconstruct historical male abundances from 1973–1998. The trawl survey has been conducted annually since then, adding an additional 23 years of estimates to the survey time series. Trawl survey stations have been added, removed, modified, and in some years a station may not have been sampled due to unforeseen circumstances, leading to total abundance estimates based on different background information. To develop a single source of comparable abundance estimates, stations and station areas used for area-swept estimates have been standardized from 1988–2021. For each district or section standard stations were assigned to a high or low CPUE (number of crab caught per kilometer towed) stratum. Estimated abundance of each stratum was calculated by applying the mean CPUE of sampled stations, weighted by station size, to the overall area of the stratum. Strata abundances were summed by district or section. This allows the entire area of the survey to be considered, even when a station was not sampled. There are currently 34 years of consistent, standardized trawl survey data that contribute to understanding the productivity of these stocks. Annual area-swept abundance estimates of mature male and female Tanner crab abundance show substantial fluctuations of over 10 million crab within a 3-year period. Long-term (1988–2021) average abundance indices of mature males were determined and compared to previous long-term average abundance indices in use through 2022. Of the 12 management units considered, the mature male long-term average increased in 4 management units and decreased in 8. Long-term average abundance indices of mature females were also determined using the standardized 1988–2021 data. However, no comparisons to previous averages were made because the population reconstruction done in 1999 did not consider females.