Science Advisory Report 2023/038

*This advice was developed in a peer review meeting in 2022 and should be interpreted within the context of the situation at that time.

Assessment of Northern Shrimp (Pandalus borealis) in Shrimp Fishing Areas 4-6 in 2021

Summary

• Resource status of Northern Shrimp was assessed based on DFO fall multi-species trawl survey data (Shrimp Fishing Areas [SFAs] 5-6), Northern Shrimp Research Foundation (NSRF)-DFO summer trawl survey data (SFA 4), and commercial catch data (exploitation rate index).
• Ecosystem status in 2J3K and 2H (SFAs 5-6) was considered by examination of available oceanographic conditions, biological community structure, predator-prey interactions, genetic composition of shrimp components, and some human impacts (including trends in fishery performance). Data on ecosystem status in SFA 4 are limited.
• It is recognized that Northern Shrimp are distributed broadly over the Northwest Atlantic Ocean, including SFAs 4-6, and that these areas are connected through larval dispersal. Rates of exchange of adults are less understood. Preliminary research demonstrates localized genetically-distinct pools that may be linked to smaller-scale oceanographic profiles (i.e., gyres). These linkages need to be considered to interpret dynamics within and among assessment areas.

Environment & Ecosystem

• The NL Climate Index indicated that 2021 was one of the warmest years on record, continuing the ongoing warming trend since 2018.
• The spring phytoplankton bloom was earlier than average in 2021, continuing a trend towards earlier blooms since the mid-2010s. The zooplankton community structure in recent years has returned to a state of higher proportion of larger copepod species (Calanus finmarchicus) which could potentially have a positive impact on energy transfer to upper trophic levels.
• Under current ecosystem conditions (i.e., low shrimp stock sizes, low ecosystem productivity, shifting back to finfish dominated structure, low shrimp per capita net production, and generally high predation pressure in SFA 6 and southern SFA 5) fishing is unlikely to be a dominant driver of shrimp stocks in SFA 6 and southern SFA 5, but it is likely a dominant driver in northern SFA 5. Ecosystem conditions in SFA 4 could not be determined.
• Given the relative impact of predation in recent years in SFA 6 and southern SFA 5, small changes in catches have the potential to be more influential on stock trajectory than they may have been in the mid-2000s. Similar analyses for northern SFA 5 do not show a consistent increase in relative impact of predation, but indicate the likely impacts from fishing have been more important than predation in recent years. There is no information on the relative impact of predation in SFA 4.

SFA 6 Pandalus borealis

• The annual commercial catch per unit effort (CPUE) declined considerably between 2015/16 and 2017/18 to the lowest levels in two decades and has increased since 2019/20, but remains below the long-term mean.
• The number of stations sampled by the DFO multi-species survey in 2021 had significant reductions. Simulated resampling of historic survey data, using 2021 survey coverage, suggest that the 2021 biomass estimates may slightly overestimate the stock status in SFA 6.
• Fishable biomass and female spawning stock biomass (SSB) indices have declined since 2020, by 20% (to 94,300 t) and 3% (to 72,900 t) respectively, and remain amongst the lowest levels in the survey time series.
• The exploitation rate index ranged between 5.5% and 21.5% from 1997 to 2021/22 and was 6.0% in 2021/22. If the total allowable catch (TAC) is fully taken in 2021/22, then the exploitation rate index will be 8.1%.
• The female SSB index is in the critical zone of the Integrated Fisheries Management Plan (IFMP) Precautionary Approach (PA) Framework for the sixth consecutive year, with a 22% probability of being in the cautious zone.
• The rebuilding plan states a maximum exploitation rate of 10% while the stock is in the critical zone. If the 2021/22 TAC of 9,534 t is maintained and taken in 2022/23, the exploitation rate index would be 10.1%.

SFA 5 Pandalus borealis

• Standardized large-vessel CPUE had varied without trend at relatively high levels for more than a decade but has been near the long-term mean since 2017/18.
• The number of stations sampled by the DFO multi-species survey in 2021 had significant reductions. Simulated resampling of historic survey data, using 2021 survey coverage, suggest that the biomass estimates in SFA 5 in 2021 show no consistent bias.
• Fishable biomass and female SSB indices have declined since 2020, by 12% (to 71,000 t) and 17% (to 42,800 t) respectively, and are amongst the lowest levels in the survey time series.
• The exploitation rate index ranged between 7.8% and 29.3% from 1997 to 2021/22 and was 11.1% in 2021/22. If the TAC is fully taken in 2021/22, then the exploitation rate index will be 20%.
• Female SSB index is in the healthy zone within the IFMP PA Framework, with 42% probability of being in the cautious zone. If the 16,080 t TAC is maintained and taken in 2022/23, then the exploitation rate index will be 22.7%.

SFA 4 Pandalus borealis

• Large-vessel standardized CPUE varied without trend over 1989–2020/21 but has been at or above the long term mean for the past 5 years.
• The NSRF-DFO shrimp survey in 2021 survey indicated an increase in biomass estimates, but the large magnitude of the increase is influenced by two large, localized sets. It is uncertain how much of this estimated increase from 2020 is due to changes in local shrimp productivity, sampling variation, or movement of shrimp into SFA 4 from neighbouring areas.
• Fishable biomass and female SSB indices have increased significantly since 2020, by 156% (to 151,000 t) and 162% (to 113,000 t) respectively, and are amongst the highest levels in the survey time series.
• The exploitation rate index ranged between 7.0% and 36.7% from 2005/06 to 2020/21 and was 5.8% in 2021/22. If the TAC had been taken, the exploitation rate index would have been 6.6%.
• In 2021, the female SSB index was in the healthy zone within the IFMP PA Framework, after four years in the cautious zone, with 8% probability of being in the cautious zone.

This Science Advisory Report is from the February 15-17, 2022 regional peer review on the Assessment of Northern Shrimp in SFAs 4-6. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2023/038 (PDF, 1,269 KB)

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