Temporal patterns in size and condition at settlement in two tropical reef fishes (Pomacentridae: Pomacentrus amboinensis and P. nagasakiensis)

Abstract

Temporal variability in the size, age, and biochemical composition of newly settled fish of 2 tropical reef species, Pomacentratus amboinensis and P. nagasakiensis, were examined over 3 recruitment seasons in the northern Great Barrier Reef, Australia. Juveniles of both species were more variable in composition (CV: 322 to 35.8%) than size (CV: 51 to 5.3%) and age (CV: 7.2 to 8.4%) at settlement. Overall, P. amboinensis settled over a range of ages from 15 to 23 d, while the larval duration of P. nagasakiensis ranged from 16 to 24 d. The biochemical composition of both species varied among lunar recruitment pulses. Strong interannual differences in the composition (principally carbohydrate and protein) of P. amboinensis juveniles were detected. This variability in nutritional condition of newly settled fish has important implications lot future patterns of post-settlement growth and development P. amboinensis and P. nagasakiensis settling during a single lunar recruitment episode (pulse) differed in length, body depth, and weight. On average P. nagasakiensis were 2 mm longer and 0.03 g heavier at settlement than P. amboinensis. P. nagasakiensis attained this larger size at settlement by means of a higher average growth rate during the larval period. Juveniles of both pomacentrid species settling at the same tune were very similar in nutritional condition. Fish settling in the first pulse of the recruitment season weighed less and contained less lipid than recruits settling in the following month. This suggests that the effect of processes in the pelagic environment controlling the accumulation of energy reserves in juvenile stages of reef fish are not necessarily species specific.