Early life-stage and adult productivity dynamics derived from a state-space stock assessment model for data-limited Thorny Skates (Amblyraja radiata Donovan, 1808) in NAFO Divisions 3LNO and Subdivision 3Ps

Thorny skate fisheries in the Northwest Atlantic are of heightened management interest because of the vulnerability of the species to fishing and their severe declines in the Gulf of St. Lawrence down to the Gulf of Maine. North of these regions in NAFO Divisions 3LNO and Subdivision 3Ps, thorny skate are the most abundant skate species and there has been directed fishing for this stock since the 1980’s. However, there is no stock assessment model to evaluate the impacts of fishery catches or to provide future catch advice to fisheries managers. We present a state-space stock assessment model which integrates length-based survey indices and total fishery catch information to estimate population dynamics, including changes in natural mortality rates. However, this is a data limited stock so our assessment model makes simplifying assumptions which we test with sensitivity analyses. We also conduct simulation analyses of the model. These results indicate that the model estimates are robust to assumptions and reliable in simulations, although we found some bias which should be acknowledged and better understood if the model is used for management advice. Our model indicates that the stock declined rapidly between 1986 and 1995 but increased since then and in 2019 the SSB was about half of the average value in 1984–1986 prior to the decline. • We present a stock assessment model for thorny skate in NAFO Divisions 3LNO and Subdivision 3Ps. • The stock declined rapidly between 1986 and 1995 but increased since then. • Harvest rates have been less than 2 % since 2011. • Projections indicated little growth of SSB during 2020–2024 for status quo catches. • Results indicate two time periods with higher M: 1) 1991–1995 and 2) 2009–2014 for ages 1–3.