Trends in age-at-recruitment and juvenile growth of cuttlefish, Sepia officinalis, from the English Channel

Abstract

Abstract The cuttlefish Sepia officinalis is an important fishery resource in the English Channel, and one of the largest stocks of cephalopods in the Northeast Atlantic. Cuttlefish live for approximately 2 years and catches consequently depend largely on recruitment. Early life stages were analysed for differences in juvenile growth and age-at-recruitment to the commercial fisheries. Recruits were sampled monthly between October 2000 and June 2003, and pre-recruits from the coastal waters of the UK and France in the summers of 2000 and 2002. Age (days) was determined from statoliths. Although most cuttlefish were recruited during autumn, there was some recruitment throughout the year. Age-at-recruitment varied significantly between season and cohort, but was consistently in the range 3–4 months, so although there was some hatching throughout the year, most cuttlefish hatched during summer. Fitted growth models indicated that the growth rates of pre-recruits (7–59 mm mantle length) were significantly higher in 2002 than in 2000. Spatial differences in growth rate were apparent in 2000, suggesting that pre-recruit growth may depend on local environmental conditions. Pre-recruits and recruits combined (7–106 mm mantle length) also showed significant variation in growth between hatching months and years. Hypotheses explaining the observed patterns of growth and recruitment are presented.