Brief review on the ecology in the north African population of arrow squid Todarodes sagittatus (Cephalopoda : Ommastrephidae)

An isolated population of Todarodes sagittatus inhabits the shelf and slope waters of North African coast from 11°45' to 26°N within the depth range 65-1100 m. This population has a 1-yr life cycle and spawns year-round, with a clear winter peak. Hatched larvae rise to the subsurface layers above the continental slope and grow there up to 12-15 cm ML. Then immature squid (10-25 cm ML) forage from May to August over the continental shelf from 18° to 25° N (depth range 100-300 m ). In this period they formed fishery concentrations. In August-October, when maturation begins, squid concentrations disperse, mature squids (males of 20-28 cm ML, females of 25-35 cm ML) descend to 400--800 (1100) m depth. Squid abundance and density of the summer foraging aggregations vary by years as well as by depth ranges. Annual Soviet catches vary from 17 to 3725 mt (1980-1991) the highest value being of) 8,000 mt (1974). Squid biomass was estimated to be 10-30 thousand mt in years of low abundance to 80-120 thousand mt in years of high abundance.