Using inshore fishery acoustic data on Atlantic herring (Clupea harengus) spawning aggregations to derive annual stock abundance indices

Abstract

Acoustic data collected during fishing activities has been used to obtain nightly biomass and exploitation rate estimates for Atlantic herring (Clupea harengus) spawning components. Beginning in 2002, fishery based acoustic data were collected on the five major fall spawning aggregations in the sGSL and nightly biomass was estimated. Derivation of an annual seasonal index of herring biomass from fishery nightly biomass estimates have been problematic because of uncertainties associated with the behaviour of herring which accumulate prior to spawning, as well as a significant proportion of missing observations. We have developed a model which addresses these issues using nightly biomass estimates derived from acoustic data collected between 2002 and 2012 from the Fisherman's Bank fall spawning component gillnet fishery in the Southern Gulf of St. Lawrence. We conclude that these estimates identify annual changes in biomass and exploitation rate in this fishery. The method is generally applicable where the fishermen's search pattern covers the range of available fish schools during a fishing trip. Using inshore fishery biomass estimated from acoustic data to derive annual stock assessment indices could lead to the introduction of the proven reserve concept and empirical reference points to be incorporated into fishery management decisions, thus making the advisory process more transparent and responsive to local herring abundance.