Evaluation of Mature Size for Tanner Crab from the Kodiak District Large-mesh Trawl Survey, 1996-2019
Author: Michael Knutson
Publisher:
Published: 2022
Total Pages: 16
ISBN-13:
DOWNLOAD EBOOKSize at male maturity is a valuable metric for sustainable management of many species. It is used to protect the reproductive viability of stocks and is often incorporated directly into commercial fishing regulations, as is the case with Tanner crab (Chionoecetes bairdi) in the Kodiak District. This metric had been estimated previously for this stock, but size at maturity can change with environmental conditions or increases in harvest pressure. This study utilized the allometric ratio between chela height and carapace width, a widely accepted nonlethal method, to classify maturity status using two different approaches. A logistic regression model was then developed to estimate the size at 50% maturity. The traditional method of classifying crab utilizing a single allometric ratio for the entire range of carapace widths estimated a mature size of 110.78 mm, within the range of previously estimated mature sizes. The recently developed method of classifying mature status using a ratio that is allowed to vary across the distribution of carapace widths estimated a slightly lower size at maturity at 109.59 mm; however, this method performs better at assigning maturity status to crab at the upper and lower end of the carapace width range. There does not appear to be compelling evidence that the current regulatory size at maturity (114 mm) needs to be adjusted because it still accurately represents the size at 50% maturity for this stock.
