Research Document 2020/045

Eastern Scotian Shelf Shrimp (Pandalus borealis): 2018–2019

By Cassista-Da Ros, M. and Cosham, J.

Abstract

The DFO-Industry survey stratified mean biomass estimate increased 1% to 23,449 mt (± 4,724 mt, 95% Confidence Interval (CI)) from the 2017 estimate of 23,382 mt (± 6,376 mt, 95% CI). The 2018 Spawning Stock Biomass (SSB, females) point estimate increased 2% to 12,599 mt, and remains below the Upper Stock Reference (USR, 14,558 mt). Based on the Precautionary Approach as it is applied to Eastern Scotian Shelf (ESS) Shrimp, the stock is considered to be in the Cautious Zone. An unchanged Total Allowable Catch (TAC) value in 2018 (2,600 mt) was applied to limit further reductions in total and spawning stock biomasses. This precautionary TAC helped to reduce both total and female exploitation to 10% and 12%, respectively. Commercial Catch Per Unit Effort (CPUE) indices declined by 16% and 4% for the Gulf and Maritimes (Standardized Nova Scotian) fleets, respectively. The trap fishery CPUE index declined by 1%, relative to 2017. The distribution of commercial catch was consistent with an increase in total biomass, with an increase in the number of areas with catch levels from <150 mt to >450 mt. Commercial and survey sample length frequency distributions, combined with modal analysis of survey data, suggest that the fishable stock is currently supported by the more abundant year-class originating between 2013 and 2014. Trends in shrimp size indices were consistent with expectations based on life history and growth rates for shrimp at moderate abundance (i.e., no evidence of slower growth or delayed sex transition that have occurred for this stock during periods with more abundant cohorts/high density). Unlike 2017, the 2018 belly-bag index of Age 1 abundance was found to be moderate. The 2013 year-class, which was first identified by a high belly-bag index in 2014 (second highest in the time series), was evident in the 2017 and 2018 main trawl survey and commercial samples, continuing to suggest good survival and growth of this cohort. Ecosystem characteristic indices suggest that present conditions on the ESS are favorable for shrimp. Bottom temperatures derived from the June shrimp survey are lower in 2018 compared to 2017. There is some stability in indices of abundance of sympatric species, which suggest that the environment is becoming more favorable for cold water species. The overall mean indicator, summarizing 24 indicators, is in the yellow for 2018 after 2 years in the red zone, largely due to positive changes in abundance, combined with increasing indices contributing to production and ecosystem characteristic categories. Small increases in the total and spawning stock biomass indices are consistent with the expectation that the 2013 year-class has recruited to the fishable component of the stock.

Research Document 2020/045 (PDF, 10 742 KB)

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