Research Document 2020/072
Information in support of establishing new Limit Reference Points for Northern Shrimp (Pandalus borealis) and Striped Shrimp (Pandalus montagui) stocks in the Western Assessment Zone and updating the existing Limit Reference Points for the Eastern Assessment Zones
By Walkusz, W., and Atchison, S.
Abstract
The Precautionary Approach (PA) is a general philosophy to managing threats of serious or irreversible harm where there is scientific uncertainty. An implementation of this approach, in the form of the PA Framework, serves as a foundation for the establishment of Limit Reference Points (LRPs), below which productivity is sufficiently impaired to cause serious harm to a fishery. Fisheries and Oceans Canada (DFO) has committed to implementing a PA Framework (DFO 2006) in the management of the Northern (Pandalus borealis) and Striped (P. montagui) shrimp fisheries located in Hudson Strait and Ungava Bay (Western Assessment Zone; WAZ). To support these efforts, this document provides directions for establishing of LRPs and suggests the Upper Stock Reference Points (USRs) for these stocks. This document also discusses updated LRPs and suggests USRs for the Northern and Striped Shrimp fisheries in Davis Strait (Eastern Assessment Zone; EAZ). Two approaches to establishing the LRPs are considered herein: 30% and 40% of the geometric mean of female spawning stock biomass (SSB).
In the WAZ, based on a 6-year time series, new LRPs based on a 30% scenario were calculated as 3,100 and 9,200 t for Northern Shrimp and Striped Shrimp, respectively. The 40% scenario in the WAZ would result in new LRPs of 4,100 and 12,300 t for Northern Shrimp and Striped Shrimp, respectively. New proposed USRs in the WAZ, based on a 6-year time series and calculated at 80% of the geometric mean of SSB, would be 8,200 and 24,600 t for Northern Shrimp and Striped Shrimp, respectively.
Similarly in the EAZ, two scenarios for calculating updated LRPs were also considered (i.e., 30% and 40% of the geometric mean of SSB). Based on a longer, 11-year time series, updated LRPs based on a 30% scenario were calculated as 11,800 t (increase from 6,800 t) and 2,300 t (no change) for Northern Shrimp and Striped Shrimp, respectively. The 40% scenario in the EAZ would result in updated LRPs of 15,800 t (increase from 6,800 t) and 3,100 t (increase from 2,300 t) for Northern Shrimp and Striped Shrimp, respectively. The updated USRs, based on 80% of geometric mean of SSB, in the EAZ are proposed at 31,600 t (increase from 18,200 t) for Northern Shrimp and 6,100 t (no change) for Striped Shrimp. The updated reference points for the EAZ reflect a longer time series (11 years versus 3 years as previously explored) and expanded spatial coverage to reflect current assessment extent.
The intent of this document is to serve as a source of supporting information to provide advice to DFO Resource Management, consistent with the Department’s PA Framework in support of the sustainable management of these fisheries.
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