The biology of the ommastrephid squid, Todarodes sagittatus, in the north-east Atlantic

Todarodes sagittatus (N=1131) were opportunistically sampled from commercia l and research trawling in Irish and Scottish waters between 1993 and 1998. Tl, ic results suggest that the species is common in deep waters (> 200 m) to the west of Ireland and Scotland, particularly in late summer and autum n. The size of squid caught was related to depth, with larger squid caught deeper, and is indicative of an ontogenetic, batymetric migration. Females were more common sex ratio 1,00:0.46), and attained a larger maximum size ( 520 min mantle length ML)) than males (426 min ML). Mature fernales (360-52 0 min ML) were caught in deep water ( > 500 m), between March and November. with a large catch of mature females taken off the west coast of Ireland i n August 1996. Mature males (300-426 mm) were found from August to November . Potential fecundity was estimated to range from 205,000-523,500 eggs fema le(-1). Putative daily increments in statoliths indicated a life cycle of s lightly over a year, with rapid growth of approximately 1.8 mm d(-1) during subadult and adult life. Fish were the most important prey of T. sagittatu s and 17 fish prey taxa were identified, of which pelagic species were the most important.