Life cycle, demography and reproductive investment in the myopsid squid Alloteuthis subulata

Abstract

Eleven monthly samples of the myopsid squid Alloteuthis subulata were collected from the English Channel with a small otter trawl in 1985-86. Squid were sexed and assigned a maturity stage. Measurements were made of mantle length and dry weight of gonad and somatic tissue. Maximum length of life for squid from this population is ca 1 yr. Immature squid are recruited into the population twice during the year, in spring and summer. Males and females start to mature at 30 to 40 mm mantle length. The demography of the population is complex, and more difficult to interpret for males. There were apparently 3 spawning groups of females in the year sampled. The length exponent for body weight is very low in both males and females. Males mature earlier than females and male gonad weight is poorly correlated with body weight in squid > 90 mm mantle length. Gonad weight increases logarithmically in relation to total body weight in females but gonad production is not appreciable until mantle length exceeds 100 mm. The gonad accounts for ca 25 O/O of the body mass of females at the maximum mantle length of 140 mm. This suggests that A. subulata, In common with some other cephalopods, has a low reproductive effort by comparison with the lifetime reproductive effort of species of benthic iteroparous mollusc.