Life-history, ecology and fishery of Sepia officinalis in the western Mediterranean

Abstract

Cephalopods constitute important resources for different Mediterranean fisheries such as trawl, artisanal and recreational fleets. Cuttlefish (Sepia officinalis) has been caught there from ancient times on and holds an important seasonal artisanal fishery in the Balearic Islands (western Mediterranean). This fishery takes advantage of the reproductive migration to coastal waters of large, mature individuals, even though the species is also taken by bottom trawlers throughout the year. In this study we used data from the following sources to analyze different aspects of cuttlefish biology, ecology and fishery in the western Mediterranean: 1) monthly biological and size samplings of individuals caught by artisanal boats (2007-08); 2) size samplings on board ofcommercial bottom trawlers (2001-11); 3) biological and size samplings on spring scientific surveys (2001-11); and 4) official fishery statistics from 1965 to the present. The main objectives of this study are twofold. First, use all this information to generate a comprehensive insight on the life cycle of this species linking ecology and life-history traits to seasonal fishery trends. Secondly, analyze interannual variations on landings and the relationship with different environmental parameters (e.g. moon, temperature, climatic indices). Biological (N=950 individuals) and size frequency samplings were used to estimate different species and population parameters such as length-weight relationships, sex- ratio, population structure and dynamics, gonadosomadic index and fecundity. The vast majority of individuals caught by the artisanal fishery between January and July were sexually mature, which confirms the reproductive migration to coastal waters during spring. The clear seasonal trend observed in cuttlefish landings also tallies with this migration, since catches show a marked peak in March-April. Although landings display a sawtooth like pattern from 1965 to 2011 with historical maximums in 1991 and 2005, there is a general increasing trend with time, especially from mid-1990s