Age and growth of arrow squid Todarodes sagittatus (Cephalopoda: Ommastrephidae) sampled in summer in Atlantic Moroccan waters

Statoliths of arrow squid Todarodes sagittatus were sampled in a fishery region at 21°–24°N off the Atlantic Moroccan coast during July 1995. Most squid were immature. Age and growth of the squid were studied by examining the growth increments within statoliths of 76 specimens (mantle length, ML, ranging from 90 to 280 mm). Characteristics of the growth zones in the ground statoliths are described. The statolith structure was typical of that for other ommastrephid species. The maximum ages (Number of growth increments (NGI))were 231 d (280 mm ML) for females and 213 d (210–250 mm ML) for males. Females grew faster than males in weight (BW) and in length. Growth in length in this period of the life cycle was best described by the linear function, ML(mm) = 1.180 NGI (d) −13.265, for females (n = 40; r² = 0.709), ML (mm) = 1.057NGI(d) −9.344 for males (n = 36; r² = 0.634). Growth in weight was best described by the power function, BW(g) = 0.00002 NGI(d)^3.085, for females (n = 40; r² = 0.625), and BW(g) = 0.00003 NGI(d)^2.889, for males (n = 36; r² = 0.534). The daily growth rates were 1.3 mm d⁻¹ and 0.3–2.7 g d⁻¹. The investigated squid hatched from November to April with a peak in winter (December–February).