Summary of the 2015, 2016, and 2017 Herring Acoustic Surveys in NAFO Divisions 4VWX

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. During the years 2015 to 2017, 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 was estimated by summing these results. Six structured surveys were conducted in Scots Bay in 2015, six in 2016, and eight in 2017. Five usable structured surveys were conducted on German Bank in both 2015 and 2016. There were four (plus two) surveys on German Bank in 2017. The September 17 survey was initially excluded because it was nine days after the previous one; however, this resulted in a 28-day gap before the next acceptable survey. Subesquently, at the 2018 assessment meeting, this survey was included. One acceptable structured survey was completed in the Trinity Ledge area in 2015, followed by three in 2016 and four in 2017. There were no structured surveys conducted in 2015 or 2016 for Spectacle Buoy; however, three fall surveys were completed in 2017. In most cases, these surveys provided good coverage of the spawning areas consistent with established protocols. In 2015, the biomass estimate decreased to approximately 4% of the 2014 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 2016 estimate for the same overall areas decreased 29% of the 2015 estimate, while in 2017 the biomass increased (20%) above the 2016 estimate. The 2014 and 2015 estimates were above the long-term average since 1999, while the 2016 and 2017 biomass estimates are below the long-term average. 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 9% since 2011. The Trinity Ledge 2017 spawning biomass has increased substantially to be above the long-term average; however, since 2006, the estimates have been well below the average. The recent large fluctuation in the SWNS/BoF spawning complex is occurring in the Scots Bay area; however, the long-term trend is upward. 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. Four (2013), six (2014), and six (2017) surveys were completed for Little Hope, as well as, four (2015), seven (2016), and 10 (2017) surveys for Halifax/Eastern Shore. No surveys were completed in the Glace Bay area. In Little Hope, a substantial increase in the spawning biomass estimate to a historic high was observed in 2015 (145,395 t), a three-fold increase over the 2014 estimate. There was a 57% decrease in the estimate in 2016 (61,408 t) followed by an 8% increase in 2017 to 66,815 t. The estimate is above the long-term average of 38,659 t. The total spawning biomass estimate for the Halifax/Eastern Shore area demonstrated a seven-fold increase from 9.586 t (2014) to 68,564 t (2015). While the biomass decreased to 54,352 t (2015) and 58,681 t (2017), it is above the recent five-year average of 39,602 t, and above the long-term average since 1998 (33,606 t). No survey was completed in Glace Bay during the 2015–2017 period.