Science Advisory Report 2024/064

Assessment of Atlantic Herring in NAFO Division 3KLPs to 2021

Summary

Overview

• During this assessment, stock status indices were updated for Bonavista Bay-Trinity Bay and Fortune Bay using data from the spring research gillnet program; the results of a similar short-term program in Placentia Bay were also presented. Results of recent acoustic surveys in White Bay-Notre Dame Bay, Bonavista Bay-Trinity Bay, St. Mary’s Bay-Placentia Bay and Fortune Bay were reviewed. There was not enough recent data to provide an update for Conception Bay-Southern Shore.
• Inshore acoustic surveys of northeast and south coast herring stock complexes were used to produce biomass indices from 1983 to 2001. These surveys were reinstated in 2019 and the results were presented at this assessment.
• The ecosystems in the Newfoundland and Labrador (NL) bioregion continue to experience overall low productivity conditions, with total biomass well below pre-collapse (1980s) levels. While offshore ecosystem indicators (e.g., biomass trends, stomach content weights) in recent years appear to be improving, current levels are still below those of the mid 2010s. The overall picture for herring, with declines in the late 1980s and early 1990s and reduced productivity since, is generally consistent with the trends observed in offshore surveys.
• The NL climate experiences important fluctuations at decadal time scales, with potential impacts on ecosystem productivity and herring recruitment. Since 2018, a warming trend has been observed, with 2021 being one of the warmest years on record. Since the mid‑2010s, there has been a general trend toward earlier spring blooms, returning to the long‑term mean. Over the same time period there has been a change in the zooplankton community composition characterized by low abundance of large, energy-rich Calanus spp. copepods and high abundance of small copepod taxa in NAFO Divisions 3KLPs.
• There was an overall decline in average length-at-age of herring since the 1980s. Within this pattern of decline, there was an increase for most age classes from 2020 to 2021 with the notable exception of age 4s (2017 year class), which saw a sharp decrease. Length at 50% maturity (L50) of the 2017 year class was at a time-series low in 2021 while age at 50% maturity (A50) increased, returning to the relatively high levels observed through the late‑2000s.

White Bay – Notre Dame Bay

• The commercial catch at age in 2021 had a high proportion of young (age 3–5) spring spawners. The acoustic survey biomass index for 2020 (13,219 t) was similar to what was observed in the last survey in 1998 but much lower than the 1980s; samples collected during the survey were comprised of small herring indicating potential strong recruitment.

Bonavista Bay – Trinity Bay

• Catch rates in the spring research gillnet program in Bonavista Bay-Trinity Bay increased substantially in 2021, after being well below the reference period (1990–2005) mean for the previous five years. This increase was driven by high catch numbers of age 4 herring, which also composed a high proportion of the commercial catch in 2021. The stock status index increased after decreasing in 2019 and 2020. The recruitment index (age 4 herring) was at a time-series high for both spring and fall spawners in 2021.
• The biomass index for Bonavista Bay-Trinity Bay derived from the fall 2019 acoustic survey (26,589 t) was similar to levels observed in the 1990s; however, the value from the fall 2021 survey (9,970 t) was the lowest value in the time series.

St. Mary’s Bay – Placentia Bay

• Catch rates in the recent short-term research gillnet program in Placentia Bay were below the reference period mean from 2018 to 2021, but were slightly higher than those observed in the early 2000s. Age 4 herring comprised over 30% of the catch in 2021 and the recruitment index (age 4 herring) was above average for both spring and fall spawners.
• The biomass index from the winter 2021 St. Mary’s Bay-Placentia Bay acoustic survey (2,407 t) was the second lowest in the time series, slightly higher than what was observed in 2000 (2,000 t). Both of these surveys took place in March and may have missed the over‑wintering aggregations which were typically observed during past surveys completed in January-February.

Fortune Bay

• Catch rates in the spring research gillnet program in Fortune Bay increased slightly in 2020 but declined in 2021, remaining well below the reference period mean. The catch at age continued to be dominated by a single year class (2012) in 2019 and 2020, however age 4 herring (2017 year class) comprised over 30% of the catch in 2021. The stock status index declined in 2021 after a slight increase in 2020. The recruitment index (age 4 herring) in 2021 was above average.
• The biomass index for Fortune Bay (5,425 t), derived from the winter 2020 acoustic survey, was higher than the last survey index value in 2001 (3,452 t) but significantly lower than the two previous (18,885 t and 30,408 t in 1997 and 1999, respectively).

This Science Advisory Report is from the October 4-5, 2022, regional peer review on the Assessment of NAFO Subdivisions 3KLPs Herring virtual meeting. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2024/064 (PDF, 1,322 KB)

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