Stochastic population dynamics of beaked redfish (Sebastes mentella)

No abstracts are to be cited without prior reference to the author.

The beaked redfish in the Barents Sea is at historical low abundance levels as a result of previous overexploitation and is considered as vulnerable by the Norwegian red list. The management of the population is currently based on survey data that only indicate abundance trends, and no analytical assessment is done. Using a Bayesian modelling framework, we have fitted an agestructured stochastic population model to catch and survey data. The model accounts for observation errors, separates natural mortality from fishing mortality, estimates important population dynamical parameters, and provides age‐specific estimates of abundances for ages 6–18 years between 1992 and 2009. Our results indicate that the population increased from 317 (95% CI 188,523) to 824 (316,1723) million individuals during 1992–1997, and gradually decreased to 227 (109,433) million individuals in 2009. The last strong cohorts were born in the late 1980s and early 1990s and the population have subsequently shifted the age distribution from being dominated by young individuals to being dominated by old individuals. Using estimated parameters, assuming no harvesting, generating recruits from a Ricker stock–recruitment curve, and conditioning on the current estimated age distribution, we constructed a population prediction interval by stochastic simulations of the adult population size 100 years forward in time. The population prediction interval indicates that the adult population is expected to decrease to a minimum of 83 (33,343) million individuals in 2014. If harvest is terminated, subsequent years are predicted to demonstrate an increase in adult abundance because of increased contribution to recruitment from the strong cohorts born in the late 1980s and early 1990s.