Using artificial devices for identifying spawning preferences of the European squid: Usefulness and limitations

Sustainable management of exploited stocks demands, among others issues, to identify the spawning spatio-temporal patterns and eventually to protect the spawning grounds of the target species. Squid seems to aggregate at this crucial period of the life-history, which implies increasing vulnerability to fishing. Unlike those of other loliginid species, the spawning preferences of the European squid are largely unknown because finding egg clutches of this species in the wild is challenging. Validated records from research programs are virtually inexistent but unsystematic records from, for example fisherman, suggest that squid spawns regularly on artificial structures. Here, we report for first time a description of the spatio-temporal pattern of squid spawning on artificial devices (ADs). Thirty ADs were deployed over one year at a marine reserve (Cabrera National Park). ADs were distributed covering the three main types of benthic habitat, and ranging from 5 to 50 m depth. ADs were sampled monthly. Three main patters have been evidenced: (i) squid would prefer sandy bottoms for spawning, (ii) spawning would peak in spring, and (iii) squid would expand their spawning areas to shallower waters during the coldest months. It is debatable to extrapolate these patterns to those actually takes place in natural conditions. However, given the heavy fishing effort exerted on squid and data scarcity, the precautionary approach supports to take data from ADs as a starting point for advising sustainable management. Assuming that spawning at ADs and at the wild are correlated, the first pattern may be related to the faster marine currents that prevail on sandy bottoms or the smaller abundance of potential predators in these habitats. The second pattern may be related with the typical phytoplankton–zooplankton cascade that, in the Western Mediterranean, takes place just preceding spring. While the third pattern is in accordance with the hypothesis that squid may undergo a spawning migration.