Science Advisory Report 2019/027

An Assessment of Northern Shrimp (Pandalus borealis) in Shrimp Fishing Areas 4–6 and of Striped Shrimp (Pandalus montagui) in Shrimp Fishing Area 4 in 2018

Summary

• Resource status of Northern Shrimp in SFAs 5 and 6 was assessed based on DFO fall multi-species trawl survey data (1996–2018). Resource status for Northern Shrimp and Striped Shrimp in SFA 4 was assessed based on Northern Shrimp Research Foundation (NSRF)-DFO summer trawl survey data (2005–2018).
• Trawl survey data for SFAs 4–6 provided information on shrimp distribution, length frequencies and biomass. Trends in fisheries performance were inferred from total allowable catch (TAC), commercial catch to date, fisher catch per unit effort (CPUE) and fishing patterns.
• Research on larval dispersal modeling within SFAs 4–6 indicated strong downstream larval connectivity and that a majority of recruits in a particular SFA may come from SFAs farther north. It also indicates low larval shrimp retention in SFAs 4 and 5, and higher larval retention in SFA 6.

Environment

• Early life history and adult stages of shrimp depend on phytoplankton (indirect) and zooplankton (direct) prey for feeding and nutrition. The key physical drivers indicate reduced primary and secondary inputs of the ecosystem (e.g., biomass) in recent years and changes in zooplankton community structure that may impact the transfer of energy to higher trophic levels across SFAs. 
• Ocean physical conditions generally exhibited cold anomalies near the surface and warm anomalies near the bottom in SFAs 4–6. As a consequence, the area of the bottom thermal habitat (2–4°C), typically inhabited by Northern shrimp, was above the climatological averages.

SFA 6 Pandalus borealis

• TAC was reduced by 63%, to 10,400 t, from 2016/17 to 2017/18 and further, by 16%, to 8,730 t in 2018/19.
• The annual commercial CPUE declined considerably in recent years to the lowest levels in two decades and has remained low.
• Over 1996 to 2018 the fishable biomass index averaged 393,000 t and in 2018 the fishable biomass index was 89,600 t, a 3% increase from 2017 and the second lowest level in the time series.
• Over 1996 to 2018 the female spawning stock biomass (SSB) index averaged 246,000 t and in 2018 the SSB index was 66,800 t, a 27% increase from 2017 but still amongst the lowest levels in the time series.
• The exploitation rate index ranged between 5.5% and 21.5% from 1997 to 2018/19, and has averaged 15.7% in the last five years. If the TAC is fully taken in 2018/19 then the exploitation rate index will be 10%.
• The female SSB index is currently in the Critical Zone of the integrated Fisheries Management Plan (IFMP) Precautionary Approach (PA) Framework with greater than 99% probability.
• The IFMP states that the exploitation rate should not exceed 10% while the female SSB index is in the Critical Zone. Should the 2018/19 TAC of 8,730 t be maintained and taken in 2019/20 the exploitation rate index will be 9.7%.

SFA 5 Pandalus borealis

• TAC was reduced by 14%, to 22,000 t, from 2016/17 to 2017/18 but was increased by 17% to 25,630 t in 2018/19.
• Standardized large-vessel CPUE over the last five years has varied without trend at relatively high levels.
• Over 1996 to 2018 the fishable biomass index averaged 133,000 t and in 2018 the fishable biomass index was 80,100 t, a 43% decrease from 2017 and the second lowest level in the time series.
• Over 1996 to 2018 the female SSB index averaged 64,800 t and in 2018 the SSB index was 38,400 t, a 31% decrease from 2017 and the second lowest level in the time series.
• The exploitation rate index varied without trend with a median value of 15% from 1997–2018/19. If the TAC is fully taken in 2018/19 then the exploitation rate index will be 18.2%.
• Female SSB index is in the Cautious Zone within the IFMP PA Framework with 51% probability. If the 25,630 t TAC is maintained and taken in 2019/20, then the exploitation rate index will be 32%.

SFA 4 Pandalus borealis

• PA reference points have been revised from the previous assessments in accordance with adjustments to a reduced survey area to exclude the Hatton Basin Marine Refuge, which is no longer surveyed. The PA framework itself has not changed.
• TAC was increased by 5%, to 15,725 t, from 2016/17 to 2017/18 and was unchanged in 2018/19. The TAC has been fully taken.
• Large-vessel standardized CPUE varied without trend near the long-term mean (1989–2017/18).
• Over 2005 to 2018 the fishable biomass index averaged 103,000 t and in 2018 the fishable biomass index was 42,100 t, a 46% decrease from 2017 and the lowest level in the time series.
• Over 2005 to 2018 the female SSB index averaged 63,700 t and in 2018 the SSB index was 32,200 t, a 39% decrease from 2017 and the lowest level in the time series.
• The average exploitation rate index was 17.4% for 2014–2017 and was 35.7% in 2018/19.
• Female SSB index in 2018 was in the Cautious Zone within the IFMP PA Framework with a 7% probability of having been in the Critical Zone.

SFA 4 Pandalus montagui

• The Pandalus montagui by-catch limit of 4,033 t has not been taken in the past six years.
• Over 2005 to 2018 the fishable biomass index averaged 27,800 t and in 2018 the fishable biomass index was 54,400 t, a 23% increase from 2017 and the highest level in the time series.
• Over 2005 to 2018 the female biomass index averaged 21,600 t and in 2018 the female biomass index was 46,500 t, a 33% increase from 2017 and the highest level in the time series.
• If the by-catch limit had been taken, the exploitation rate would have been 7.4% in 2018/19.
• There is no IFMP PA Framework for this resource.

This Science Advisory Report is from the February 12-13, 2019 Northern and Striped Shrimp Assessment. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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