Research Document 2018/052

Assessment of the NAFO Division 4T southern Gulf of St. Lawrence Atlantic herring (Clupea harengus) in 2016 and 2017

By McDermid, J.L., Swain, D.P., Turcotte, F., Robichaud, S.A., and Surette, T.

Abstract

Atlantic Herring (Clupea harengus) in NAFO Division 4T, referred to as the southern Gulf of St. Lawrence (sGSL), consists of two spawning components, spring spawners (SS) and fall spawners (FS). This document presents the most recent information on trends in abundance, distribution, and harvest for the SS and FS herring components. This includes catch-at-age and catch-per-unit-effort (CPUE) indices, fisheries-independent acoustic indices, catch rate index from the experimental gillnet survey, mesh selectivity, and catches in the multi-species bottom trawl survey of the sGSL. The data and indices are reported for the sGSL for the SS and regionally-disaggregated (North, Middle, and South regions) and overall for the FS where applicable.

SS were assessed using a virtual population analysis (VPA) which allowed for time-varying catchability to the gillnet fishery. The model estimated that SS spawning stock biomass (SSB) has been in the critical zone of the Precautionary Approach (PA) framework since 2004. The median SSB at the start of 2018 is estimated to be approximately 12,000 t, 65% of the limit reference point (LRP = 19,250 t). The instantaneous rate of fishing mortality (F) on aged 6 to 8 year old SS herring exceeded the removal reference level (F0.1; F = 0.35) until 2012. Under various recruitment scenarios (low, mixed, or high recruitment), SSB is expected to decrease at any catch options over 500 t for the next two years. By 2027, the probability of exceeding the LRP was most favorable under the high recruitment scenarios and low catches (<1,500 t), however under the low recruitment scenarios even with no catch there was only a 13% probability of SSB exceeding the LRP.

FS were assessed as regionally-disaggregated populations using a VPA which allowed for time-varying catchability to the gillnet fishery. Estimated SSB has been declining in all three regions in recent years, though it increased in the South over the last two years. Summed over all three regions, SSB at the start of 2018 is estimated to be approximately 112,000 t with a 97% probability of being within the cautious zone of the PA framework (SSB is below the upper stock reference (USR = 172,000 t)). Averaged over all regions, F of aged 5 to 10 exceeded F0.1 (F=0.32) from 1994 to 2011, but remained below since 2012. The median projected value of SSB at the start of 2020 remained below the USR at all catch levels between 10,000 and 50,000 t, with the probability of being below the USR varying from 90% at 10,000 t to 99% at 50,000 t. The probability that F of aged 5 to 10 FS will exceed F0.1 in 2019 is estimated to increase from 0% at catches of 10,000 t to 99.6% at 50,000 t.

Complete document (PDF, 9,770 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.