Research Document 2020/044

Eastern Scotian Shelf Shrimp 2016–2017

By Broome, J., Covey, M., Nickerson, K., and Hardie, D.

Abstract

The DFO-Industry survey stratified mean biomass estimate declined 14% to 25,584 mt (± 5,079 mt, 95% Confidence Interval [CI]) from the 2015 estimate of 29,642 mt (± 7,324 mt, 95% CI). The 2016 Spawning Stock Biomass (SSB, females) point estimate declined 11% to 13,223 mt, and is now below the Upper Stock Reference (USR, 14,558 mt). Based on the precautionary approach as it is applied to Eastern Scotian Shelf Shrimp, this places the stock in the Cautious Zone. A 28% reduction in the 2016 Total Allowable Catch (TAC) (from 4,500 in 2015 to 3,250 mt) was applied to reflect reduced total and Spawning Stock Biomass. The precautionary TAC reduction helped to reduce both total and female exploitation to 12% and 16%, respectively. Commercial Catch Per Unit Effort (CPUE) indices declined by 4% and increased by 3%, for the Gulf and Maritimes (Standardised Nova Scotian) fleets, respectively. The trap fishery CPUE index declined by 22%, relative to 2015. The distribution of catch was consistent with a declining resource, where areas representing all catch rate levels have been reduced. Commercial and survey sample length frequency distributions, combined with modal analysis of survey data, suggest that the fishable stock is currently supported by the less abundant year classes originating between 2009–2012. 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). Similar to 2015, the 2016 belly-bag index of Age 1 abundance was found to be very low. The 2013 year class, which was first identified by high belly-bag index in 2014 (2nd highest in the time series), was evident in 2015 and 2016 main trawl survey and commercial samples, continuing to suggest good survival and growth of this cohort. The 2013 year class is expected to begin recruitment to the Spawning Stock Biomass in 2018. Ecosystem characteristic indices suggest that present conditions on the Eastern Scotian Shelf are not favorable for shrimp. Bottom temperatures derived from the June shrimp survey remained at high levels in 2016. Low or decreasing indices of abundance of sympatric species continue to suggest that the environment is becoming less favourable for coldwater species. The overall mean indicator, summarizing 24 stock indicators, remained yellow for 2016 largely due the ongoing downturn in abundance, combined with declining indices contributing to production and ecosystem characteristic categories. Continued declines in the total and Spawning Stock Biomass indices are consistent with the expectation that the 2007–2008 year classes have reached the end of their life-span, and that the succeeding year classes (2009–‍2012) are not highly abundant..

Research Document 2020/044 (PDF, 1,939 KB)

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