Growth rate of larval Sardinops sagax from ecosystems with different levels of productivity

Otolith increment data were used to age larval Sardinops sagax from shelf waters between 118°E and 137°E off southern Australia. Maximum and mean growth rates up to an age of 30 days, estimated from a Laird-Gompertz model, were 0.62 and 0.48 mm day^-1, respectively. The growth rate of larval S. sagax from southern Australia was less than, or at most comparable to, those estimated from the substantially more productive upwelling systems of southwestern Africa, the central coasts of North and South America, and inshore of the Kuroshio system east of Japan. The lower productivity of the sardine habitat off southern Australia could be expected to manifest as fewer and/or less extensive patches of suitably dense plankton, or lower levels of sufficient food availability, which results in the lower growth rate of larvae. This probably causes higher mortality and, along with slower growth rates of post-recruit stages, may therefore contribute to the low stock size of sardines in southern Australia. Nonetheless, the similarities in growth rates of larvae within a single species over widely separated regions suggest such rates fall between predetermined bounds, limited by starvation at the lower end and an ontogenetic maximum at the other.