Demographic and risk analyses of spiny dogfish (Squalus suckleyi) in the Gulf of Alaska using age- and stage-based population models

摘要

Demographic models are useful tools for assessing data-limited species and may be an appropriate alternative to cohort analyses for sharks due to their long-lived, slow-growing nature. In this study, age- and stage-based demographic analyses were conducted to examine the intrinsic rebound potential (r) and potential risk of fishing for spiny dogfish (Squalus suckleyi) in the Gulf of Alaska. Monte Carlo simulations were conducted to incorporate input parameter uncertainty. For an unfished population, r was estimated to be 0.020.03 year~(-1). Fishing mortalities (F) of F=0.04 and 0.03 (age- and stage-based models respectively), resulted in r=0, indicating that populations fished at higher F are not sustainable. Harvest strategies targeting juveniles (age-based model) and subadults (stage-based model) caused the highest risk of the population falling below defined thresholds (BMSY, B40% and B50%) after 20 years. The age- and stage-based models provided similar estimates of r and sustainable fishing mortality, suggesting that the stage-based model is an appropriate substitute for the age-based model in this case. S. suckleyi and the closely related S. acanthias are often harvested around the world and this modelling approach could be useful to the management of these species and other sharks where data is limited.