Efficacy of using multiple acoustic systems to quantify Atlantic herring (Clupea harengus) aggregation metrics before and after fishing events.

Abstract

The use of midwater trawls to harvest Atlantic herring (Clupea harengus) in the Gulf of Maine has been a controversial topic for many years. A majority of the concern revolves around the potential physical disruption of Atlantic herring aggregations and the potential impact on ecological processes and other industries (e.g., other fisheries and eco-tourism) that rely on these aggregations. Preliminary acoustic data collection in fall 2008 using a combination of Simrad ES60 echosounders (38 and 120 kHz) and a Simrad SP90 omni-directional sonar (20–30 kHz) showed promise for quantifying herring aggregation metrics. In this presentation, we report on a pilot study conducted in the summer of 2009 that uses these acoustic systems to quantify and describe herring aggregations before and after midwater trawling with a pair of fishing vessels. We used a systematic grid design to survey an area continuously for 24 h both before and after pair trawl fishing over multiple fishing trips. We report on the efficacy of using acoustic systems to quantify the potential impacts of fishing on herring aggregations and discuss the next steps to fully evaluate these potential impacts at spatial and temporal scales relevant to the fishery.