Several ontogenetic growth models were fitted to size-at-age data of twelve species of squid from the recent suborders Myopsina and Oegopsina. These squid represent different habitats of the world ocean -from shelf to meso-and bathypelagic waters and from tropical to polar regions. Two main criteria were used in selecting the squid: large sample size (>150 individuals) and wide range of ontogenetic coverage (>2/3 of the whole ontogenesis). The growth models used were the exponential, Gompertz, Schnute and ad hoc two-stage models. They were fitted to size-at-age data using maximum likelihood for estimation and Akaike weights for identification. In all species, the 4-parameter Schnute or the 3-parameter Gompertz models provided the best fit. Size at the inflection point of the growth curve for most squid was smaller than size at 50% maturity, suggesting that maturation is not a major cause of the change in growth rate for these species. Mathematical and statistical procedures to calculate standard measures of growth, such as the instantaneous relative rate of growth, G, which are valid for all continuous growth models, are also presented.

Cephalopods have become an important global food source, but their sustainable management is challenged by unique life history characteristics associated with short lifespans and semelparous reproduction, high natural mortality rates, rapid and often nonasymptotic growth, and complex population structures. Weak stock-recruitment relationships together with the time-consuming work required for age validation and high-volume annual age determinations make traditional age-based modelling impractical. We propose that the best method for cephalopod assessment involves innovative depletion models, fitted with in-season data on catch numbers and fishing effort, to produce realistic estimates of stock biomass. A “fast lane” assessment approach is suggested that includes high-frequency data collection for separate, in-season stock assessments of each cohort to ensure sustainable exploitation of these short-lived resources. However, most cephalopod fisheries are data-poor and/or lack the infrastructure and resources needed to apply depletion methods; therefore, we also present alternative assessment methods that have been recently applied worldwide. We also offer suggestions for further research on the remaining challenges of cephalopod stock assessment and management.

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