Behaviour in a bottom trawl: Moving forward to limit catches of Atlantic cod

Abstract

The iconic Atlantic cod (Gadus morhua Linnaeus, 1758) has inspired a substantial body of fishing-gear research across its geographical range, with recent efforts predominately to reduce catches of this species in fisheries where their populations are fragile. Despite their iconic status and long history of study compared to other species, our understanding of cod behaviour during the capture process in a bottom trawl remains frustratingly limited.Much of our understanding is derived indirectly through catch results, supported to a limited extent by direct observations of cod in situ or held in laboratories. In this paper, we describe four research challenges and directions that we consider critical to advance our knowledge of cod behaviour, and ultimately, to improve the selectivity of bottom trawls to reduce catches of cod. These include the resurrection of behavioural research to directly observe and measure their reaction and sensory capabilities, and improved interpretation of their behaviour in response to a bottom trawl. It is also our view that progress in limiting catches of cod should emphasize stimulating avoidance in advance or at the mouth of an approaching bottom trawl, rather than retrospectively attempting to do so after they have entered the trawl mouth.