Author: Benjamin Daly

Publisher:

Published: 2020

Total Pages: 54

ISBN-13:

The Alaska Department of Fish and Game (ADF&G) harvest strategy for Bering Sea Tanner crab has evolved over the past 40 years in response to fluctuations in biomass, advancements in understanding of Tanner crab biology, and continued improvements in assessment modelling approaches. Although the intent of all harvest strategy changes was to improve the stability of this fishery and minimize closures, this fishery has been closed 5 out of the last 10 seasons and currently has the most complicated strategy of all the Bering Sea Aleutian Islands (BSAI) crab stocks. In collaboration among ADF&G, the University of Washington, the National Oceanic and Atmospheric Administration (NOAA), and the commercial crab industry, we take a holistic approach using the most current scientific methods to evaluate and advance a new harvest strategy that explicitly incorporates conservation and economic goals. Specifically, we used a Management Strategy Evaluation (MSE) via 100-year forecast simulations to examine the ability of 15 harvest strategies to provide sustainable harvest. Additionally, we recomputed historical total allowable catches (TACs) to further understand harvest strategy performance using “real” data (i.e., not simulated data in the MSE forecast simulations). Of the 15 strategies, 7 were discarded due to conservation concerns (e.g., high probability of total fishery mortality exceeding federal overfishing limits), and two were discarded due to economic concerns (e.g., low projected catch). Because male-only policies ignore the contribution of females to the reproductive potential of the population, we focused our recommendation on polices that include consideration of mature female biomass. Of those 4 remaining policies, we recommend a harvest policy that includes a threshold for opening the fishery of 25% of the long-term (1982-2018) average of mature male biomass, a minimum (5% or 10%) and 20% maximum exploitation rate on mature male biomass adjusted for relative mature female biomass, and a 50% maximum exploitation rate on exploitable, industry-preferred size legal male abundance. Our analysis suggests these policies balance the tradeoff between conservation and economic considerations.