Catching better quality fish with novel codend technology: Precision Seafood Harvesting

Abstract

Our study describes the design and operation of a novel codend developed in New Zealand to reduce fish damage during trawling, haul back and unloading. The Modular Harvesting System (MHS) is a membrane-like fabric tube with escapement holes that replaces the mesh codend of a trawl. The terminal section of the MHS is non-porous, which allows fish to be lifted aboard in a fluid environment. During its development, the MHS was deployed on a variety of vessels (18–82 m, 300–5400 kW) across various fisheries in New Zealand. The hydrodynamic (water flow) and hydrostatic (pressure) environment created by the MHS was investigated via computational modelling, in situ flow measurement (acoustic Doppler current profiling), accelerometry and videography of fish behaviour. The graded flow reduction and open geometry of the MHS was observed to reduce the impact of factors that cause physical damage and fatigue to the catch in mesh codends. Accelerometry measurements demonstrated the MHS moved less and maintained a more stable position during trawling than conventional codends. The low damage capture environment afforded by the MHS enabled fishers and vessel owners to evolve their fishing strategies and modify onboard handling equipment to derive maximum value from their limited quota.