Age and growth of three species of clupeids from Kiribati, tropical central south Pacific

Abstract

The age and growth of three widely distributed tropical clupeids, Amblygaster sirm, Herklotsichthys quadrimaculatus and Spratelloides delicatulus at four sites in Kiribati were examined by otolith increment counts. Amblygaster sirm grew to 230 mm s.l. and 130 g and lived for up to 2 years at all sites. Herklotsichthys quadrimaculatus grew to 110 mm and 15 g and lived up to 1 year; white S. delicatulus grew to 66 mm and 2.5 g and lived for 4‐5 months. There was little difference in the rate of growth in length of any of the species at the sites, except for S. delicatulus at one site. All species grew rapidly in length at the expense of growth in weight during the early life‐stages when mortality is highest, hence reducing the time they spend in this life‐stage. The relationship between weight and age varied between the sites for H. quadrimaculatus and S. delicatulus, but these differences narrowed as fish size increased. Herklotsichthys quadrimaculatus also grew more rapidly in weight during the first 3 months than the other species. Growth comparisons between the three species showed that all grew in length at similar rates for the first 2 months. Spratelloides delicatulus became sexually mature at 2 months of age and subsequently grew more slowly than the other species. After 4 months A. sirm grew faster than H. quadrimaculatus. The rates of growth in length and weight of these species from Kiribati were compared with those from other regions of the Indo‐Pacific. There were significant differences: A. sirm grew to a larger size in Kiribati than elsewhere; H. quadrimaculatus grew at a similar rate at all sites during the first 2 months, but then the growth rate of Kiribati fish declined and they reached a smaller asymptotic size than elsewhere; S. delicatulus from Kiribati grew in length at similar rates to Solomon Islands fish, but were significantly lighter in weight at the same age. The relative growth performance of these short‐lived tropical species was compared to that of temperate clupeids. All species showed similar growth performance despite the slower growth rates of temperate species, which suggests that the clupeoids' phylogenetic conservatism in some life history traits extends to growth. Regional and local differences in growth rates of some tropical clupeids are as large as those found among most clupeid species.