Research Document - 2016/005
Summary of the 2013 and 2014 Herring Acoustic Surveys in North Atlantic Fisheries Organization (NAFO) Divisions 4VWX
By R. Singh, A. Dalton, A. Clay, and G.D. Melvin
Abstract
Automated acoustic recording systems deployed on commercial fishing vessels have been used since 1997 to document the distribution and relative abundance of Atlantic herring from industry vessel surveys and fishing excursions in the Bay of Fundy and coastal Nova Scotia area within Northwest Atlantic Fisheries Organization (NAFO) divisions 4VWX. In 2013 and 2014, regularly scheduled surveys at approximately 14 day intervals were again conducted on the main herring spawning components, and the spawning stock biomass for each component estimated by summing these results. In 2013, seven structured surveys were conduct in Scots Bay, with six conducted in 2014. Five usable structured surveys were conducted on German Bank in both 2013 and 2014. Two structured surveys were completed in the Trinity Ledge area in both 2013 and 2014. There were no structured surveys conducted in 2013 or 2014 for Spectacle Buoy. In most cases, these surveys provided good coverage of the spawning areas consistent with established protocols.
In 2013, the biomass estimate decreased to approximately 72% of the 2012 estimate for the combined survey areas of Scots Bay, Trinity Ledge and German Bank (known as the Southwest Nova Scotia/Bay of Fundy (SWNS/BoF) (4X) stock). The 2014 estimate for the same overall areas rebounded to 98% of the 2012 estimate; both the 2012 and 2014 biomass estimates are slightly (6% and 4%, respectively) above the long term average since 1999. These estimates provide mixed indications with regards to the SWNS/BoF stock. The German Bank spawning biomass estimate has decreased at an average annual rate of 8% since 2011. The Trinity Ledge spawning biomass remained below the long term average, which is consistent with the trend in the area since 2006. Most of the recent fluctuation in the SWNS/BoF spawning complex is occurring in the Scots Bay area, as the biomass in 2013 was less than half of the previous year before reaching a high in 2014 since the acoustic surveys began in 1999.
Biomass estimates from surveys of the coastal Nova Scotia spawning components for the Little Hope/Port Mouton, Halifax/Eastern Shore and Glace Bay areas were also examined. Three (2013) and four (2014) surveys were completed for Little Hope, four (2013) and six (2014) surveys for Halifax/Eastern Shore and one (2013) for the Glace Bay area. In Little Hope, a substantial increase in the spawning biomass estimate was observed in 2013 (74,532t) over the four-year low documented in 2012 (12,756t). While the 2014 spawning biomass (46,077t) was approximately 62% of the 2013 level, it is still above the most recent five-year average of 37,664t. The total spawning biomass estimate for the Halifax/Eastern Shore area demonstrated increases in both 2013 (6,870t) and 2014 (9,586t), reaching near the recent five-year average of 10,664t, but remaining well below the long term average since 1998 (28,857t). Glace Bay showed virtually no fish in the one survey completed in 2013 (50t).
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