Assessment of NAFO Subdivision 3Ps thorny skate (Amblyraja radiata)

Abstract

Bottom temperatures in NAFO Subdiv. 3Ps remained above normal between 2009 and 2019, but no data are available for 2020. Zooplankton data were also unavailable for 2019 and 2020. Satellite imagery indicated that the timing and magnitude of the spring phytoplankton bloom were normal in 2020, after two consecutive years of early onset and above-normal production. Ongoing warming trends, together with an increased dominance of warm water fishes, indicate that this ecosystem continues to experience structural changes. Thorny Skate in Subdiv. 3Ps and adjacent Div. 3LNO are considered to constitute a single stock, which is managed by Canada in Subdiv. 3Ps and by NAFO in Div. 3LNO. Life history characteristics of Thorny Skate result in low intrinsic rates of population growth; thereby leading to low resilience to fishing mortality. In Subdiv. 3Ps, reported landings by Canada and France totaled 1,059 t in 2018, and 969 t in 2019, approximately double the previous six year average catch (497 t over 2012–2017). The Canadian DFO research survey abundance index for Subdiv. 3Ps was relatively stable from 1993–2019, while the survey biomass index indicated a gradually increasing trend. Similar trends were observed in Div. 3LNO. There was no spring survey in 2020. The relative estimate of fishing mortality for Thorny Skate in Subdiv. 3Ps has been below the long-term average (1996–2019) since 2010. Relative fishing mortality in Div. 3LNO also remains low. In Subdiv. 3Ps, the abundance of Thorny Skates ≤21 cm in total length has been below average during 2018–2019. Overall, the stock recruitment index for the entire stock area in Subdiv.3Ps and Div. 3LNO has also fluctuated without trend, but has been below the long term average over 2018-2019. The Thorny Skate stock in Subdiv. 3Ps and Div. 3LNO is currently above Blim. The probability that the current biomass is above Blim is >95%. The stock biomass has been generally increasing since the mid-1990s, indicating that the stock has been able to sustain the range of catches over this period.