Jumbo squid behaviour in response to a rigid grid in the Chilean hake trawl fishery

Observations via underwater filming were obtained to improve understanding of the behavior and selection process of jumbo squid (Dosidicus gigas) in response to a rigid grid in the Chilean hake (Merluccius gayi gayi) trawl fishery in central Chile. The individual fates of jumbo squid were examined to study the efficiency of the selection system. The number of escaped versus captured specimens was quantified. During the selection process, we observed obstacles that impeded the escape process, leading to retention of jumbo squid and limiting the selectivity effectiveness. The analysis showed that 69.8% of jumbo squid escaped the net and 75.5% faced obstacles that generated retention in the sorting process. Longer retention times led to a saturation of the selection system. The target species was successfully selected by the sorting system, in which 87.1% of Chilean hake entered the codend through the grid. We discuss the need to redesign components of the selection system to improve efficiency.