Cuttlefish and squid egg deposition patterns on artificial devices and trap-like gears: implications for offspring survival and population management

Abstract

Abstract We investigated the effect of trap-like gear deployment on the survival of European squid Loligo vulgaris and common cuttlefish Sepia officinalis eggs laid on various surfaces of these gears. In parallel, a detailed assessment of the two species’ egg deposition patterns on such gears was performed with respect to both the fishing season and their preferences for artificial spawning substrates. Hemp ropes with floats were the most preferred spawning substrate for squid, whereas cuttlefish mostly deposited their egg clusters on the plastic mesh of rectangular pots. Almost no egg laying was observed on traps where netting frame was coated with antifouling paints (copper oxide or zinc pyrithione). A high proportion of squid egg mops and cuttlefish egg clusters were shown to either be lost or to die after a period of continuous operation (i.e. hauling and retrieval at frequent intervals), which exceeded egg incubation periods. It is thus advised that coastal fishers either completely avoid operating static gears, which act as artificial spawning substrates on the spawning fields or use gears with materials that are repellent for these animals to approach and lay their eggs, such as nets coated with antifouling substances.