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Method of Adjusting Crab Catch per Pot for Differences in Soak Time and Its Application to Alaskan Tanner Crab (Chionoecetes bairdi) Catches
Author(s) -
Somerton David A.,
Merritt Margaret F.
Publication year - 1986
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8659(1986)6<586:moaccp>2.0.co;2
Subject(s) - fishery , fish <actinopterygii> , statistics , zoology , mathematics , biology
The Alaska Department of Fish and Game (ADFG) establishes harvest guidelines for the tanner crab (Chionoecetes bairdi) based in part on the mean catch per pot (CPP) obtained on preseason surveys. Because CPP changes with soak time, it must be adjusted to reflect a standard soak time to avoid biased estimates of mean CPP. We propose a method for doing this based on a model describing the change over time in the number of crabs within a pot. The model can be expressed as R t = (A ‐ B)/(A t ‐ B t); R t is the catch on day 1 divided by the catch on day t; A and B are parameters. After the model is fitted to the daily catches from several pots, the predicted R t values can be used later as correction factors to estimate day‐1 catches from day‐t catches. When the model was fitted to experimental CPP data for tanner crab, the estimated day‐1 catches were closer to the observed values than estimates obtained with two methods currently used by ADFG.