Assessment of the west coast of Newfoundland (NAFO division 4R) herring (Clupea harengus) stocks in 2021

Abstract

Based on preliminary data, landings of herring from the west coast of Newfoundland (NAFO Division 4R) totaled 4,862 t in 2020 and 3,074 t in 2021, with an annual total allowable catch (TAC) of 20,000 t. The fishery experienced difficulties due to a high incidence of herring below the legal size. The proportion of spring-spawners in the landings increased from a time-series low of 1.6% in 2014 to 89.6% in 2021. The proportion of spring spawners in the summer and fall acoustic surveys also increased from an average of 7.3% for the 2009-2017 period to an average of 44.6% in 2020 (summer: 44.8%, fall: 40.6%) and 51.5% in 2021 (summer: 229 %, fall: 75.4%). Landings of spring-spawning herring in 2020 and 2021 were mainly composed of fish of the 2013 year-class (age 7-8), and to a lesser extent of fish of the 2017 year-class (age 3-4). The acoustic survey biomass estimates of spring-spawning herring in 2020 and 2021 were mainly composed of fish of the 2017 year-class (age 3-4). Landings of fall-spawning herring in 2020 and 2021 were mainly composed of fish aged 9 years and over. The acoustic survey biomass estimates of fall-spawning herring were dominated by the 2016 year-class in 2020 (age 4) and 2021 (age 5). The 2021 summer acoustic survey was dominated by fish aged 8 years and over. The mean fork length at which 50% of individuals were mature (L50) was respectively 24.5 cm and 25.4 cm for spring and fall spawners. These values are higher or near the current minimum size limit of 24.76 cm in the commercial fishery. The L50 of both spring- and fall-spawning stocks has varied around the long-term average since the 2000 year-class. Both spring- and fall-spawning herring stocks show a downward trend in mean length-at-age and weight-at-age since the beginning of the 1990s. Since 2014, the relative condition index of the two spawning stocks is below the series’ average. The condition of both herring spawning stocks is positively related to the abundance of large-bodied copepod species. The acoustic surveys estimated the highest biomass indices since the beginning of the survey in 2021 for spring spawners (122,145 t, 95% CI: ± 20,803 t) and in 2020 for fall spawners (226,005 t, 95% CI: ± 35,507 t). These values represent minimum estimates of the amount of fish available at the time of the survey. The ratio of the biomass fished over the highest biomass index estimated in the acoustic surveys was considered to be a proxy for the maximum exploitation rate. In 2020 and 2021, the maximum exploitation rate was respectively 1.1% (1.0-1.2%) and 2.4% (2.0-2.9%) for spring spawners, and 1.7% (1.4-2.0%) and 0.2% (0.1-0.2%) for fall spawners. If the 20,000 t TAC had been taken in 2020-2021, the maximum exploitation rates would have resulted in 4.5-15.6% (4.2-19.1%) for spring spawners and 1.2-6.8% (1.0-8.0%) for fall spawners. Available evidence up to 2021 (low exploitation rates, commercial and acoustic survey catch-at-age, age- and length-at-maturity) indicates that maintaining the TAC at status quo should not pose a significant short-term risk to herring stocks in 4R.