Comparison of reference points estimated using a size-based method for two high-latitude crab species in the United States and Canada

Abstract

We briefly reviewed the decision rules currently used for managing two major high-latitude crab stocks, snow crab (Chionoecetes opilio) and Dungeness crab (Cancer magister), in the United States and Canada and compared them with model-based reference points, harvest rate, and biomass proportion relative to virgin biomass, developed using species- and area-specific parameters. The model followed a size-based approach, which incorporated Beverton–Holt and Ricker stock–recruitment models and estimated mean and median reference points. The recruitment was also perturbed to generate distributions of reference points. The Beverton–Holt stock–recruitment model provided a lower harvest rate than that of the Ricker model. Harvest rates were lower for combined sexes spawning biomass than for female-only spawning biomass. Increasing the minimum size at first capture and decreasing the handling mortality resulted in increased harvest rates. Changes in fishery duration and timing of fishery open date did not change the harvest rate appreciably. The harvest rates for the Canadian snow and Dungeness crabs were mostly higher than those estimated for the Bering Sea and Southeast Alaska stocks. Reliable estimates of a number of life history parameters are lacking for both species, and hence, the results of this exercise need to be treated in a precautionary manner.

Influence of temperature on embryo developmental cycles and mortality of female Chionoecetes opilio (snow crab) on the Scotian Shelf, Canada

“…The total mortality estimate for females from larvae to instar 8 (Z p = 1.65, SD = 0.06) is consistent with the magnitudes of previously computed rates for the EBS snow crab, although higher (see Zheng, 2003 and references cited within, Siddeek et al, 2004). Total mortality from larvae to adult crab was lower (Z i = 1).…”

An adaptive management approach to an octocoral fishery based on the Beverton-Holt model

“…It has been used in studying the population dynamics of vertebrates and invertebrates, including both colonial and solitary corals (e.g., Jensen 2000; Barrowman et al 2003;Goffredo et al 2004;Siddeek et al 2004;Tsounis et al 2007). The model assumes steady state and balanced recruitment and mortality.…”

Establishing Stock Status Determination Criteria for Fisheries with High Discards and Uncertain Recruitment

“…One approach to avoid “moving targets” for stock rebuilding plans is to assume that bycatch rates will remain constant over the course of the rebuilding plan, thereby maintaining a constant rebuilding target when using MSY|fixed_discards as the basis of the min–max approach (e.g., the approach utilized for various species of crab in the U.S. North Pacific; Siddeek ; Siddeek et al. ; Siddeek and Zheng ). However, when bycatch rates are volatile and differ substantially from year to year, assuming constant bycatch could lead to projected yield streams that may not support stock rebuilding.…”

“…The approach has been widely utilized across an array of species (e.g., Pacific rockfish and crab stocks; Clark ; Siddeek ; Siddeek et al. ) and is often cited as the basis for SPR proxies worldwide. Although the approach is extremely useful when stock–recruit uncertainty limits the ability to calculate MSY, the results are still context dependent and should not be universally applied without case‐specific applications (Clark ).…”