Science Advisory Report 2014/056

Assessment of the West Coast of Newfoundland (Division 4R) Herring Stocks in 2013

Summary

• Based on preliminary data for 2013, herring catches from the west coast of Newfoundland (NAFO Division 4R) totalled 19,364 t for a TAC of 20,000 t. The quotas allocated to the large seiner and fixed gear fleets were nearly reached whereas the quota for small seiners was slightly surpassed.
• Herring catches on the west coast of Newfoundland currently consist of older fish. In 2013, the catch at age was dominated by fish aged 8+ years. For fall spawners, age 5 herring seem relatively more abundant than in recent years.
• A significant decrease in the condition index of both spawning stocks has been observed over the past three years. These two stocks have also been characterized by a clear downward trend in mean weight at age since the early 1980s.
• For spring spawners, the proportion of mature fish at length has varied little over the years. For fall spawners, the lowest proportions of mature fish at length were observed in the 1980s and 2000s, and the highest in the 1990s and 2010s.
• Based on the acoustic survey, the total biomass index for spring-spawning herring varied between 7,448 t and 14,624 t between 2009 and 2011, then plummeted to only 335 t in 2013. In 2002, spring-spawning herring represented 29.6% of the total herring abundance compared to 0.4% in 2013.
• The acoustic survey shows that the total biomass index for fall-spawning herring has remained between 85,014 t and 121,888 t since 2009.
• An environmental model suggests that the variations in the condition index, weight at age (1990-2012) and recruitment (1990-2002) of spring and fall stocks are primarily associated with fluctuations in zooplankton dynamics and physical conditions. The analysis does not reveal that spawning biomass has a significant impact on recruitment.
• Recruitment predictions based on the environmental model for the 2003 to 2012 period suggest that recruitment of both stocks dropped in the mid-2000s. This decline was more evident in spring spawners.
• According to the environmental model, the spring-spawning stock biomass varies depending on fishing mortality, recruitment (environmental effect) and the predation mortality index, whereas the fall stock fluctuates according to recruitment and the predation mortality index. The model shows that the biomass of both stocks has declined in the last ten years.
• The vast majority of herring catches now consist of fall spawners. In recent years, catches of about 20,000 t have been supported by older fish. Given the age structure of the stocks, the current catch level should not be increased for 2014 or 2015. Moreover, with the decline in older fish and no significant recruitment, it is unlikely that the current catch level can be sustained in the medium term.
• Given the ever-decreasing spring-spawning stock, it is recommended that the management measures implemented in the late 1990s remain in place.

This Science Advisory Report is from the June 11, 2014 Assessment of the 4R herring stocks in 2013. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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