CEPHALOPOD BIOLOGY IN THE FISHERIES CONTEXT

The biology of exploited cephalopod stocks is reviewed. Individual growth rates are high, slowing drastically or becoming erratic at sexual maturity. Growth estimates depend on aquarium studies and population modal analysis. In some cases, ring markings in the statolith appear to be age-related, but at present there is no generally applicable method of age determination. Sexes are separate and fertilization is normally by direct mating. Rapid maturation is followed by a single spawning season and, with few exceptions, an early death. Methods for estimation of fecundity are poorly developed. Annual recruitment to the population is essential and depends critically on each year's breeding success and the survival of eggs and hatchlings. Many cephalopod species have a planktonic stage of variable duration but no specialized larval stages. Cephalopods are carnivorous animals with very high gross growth efficiency. They are also consumed in large quantities by higher trophic levels leading to suggestions that cephalopods are potentially capable of supporting significantly increased levels of exploitation. The difficulties of modelling these populations are recognized. © 1990.