Growth of juvenile Coral Reef Damselfish: Spatial and Temporal variability, and the effect of population density

Abstract

The growth rate of juvenile damselfish (Pornacentrus nagasakiensis) was estimated by daily ageing, using otoliths, and constructing length-at-age curves or, due to a close relationship between otolith radius and fish length, back-calculating the growth rates of individual fish. The growth of juvenile P. nagasakiensis was not detectably affected by population density, whether naturally established or manipulated. In one experiment, the presence of early recruits had no detectable effect on the growth of subsequent recruits, and postsettlement growth rates even increased slightly with subsequent pulses of settlement through the first half of the summer (as water temperature increased). However, in other (nonexperimental) samples, there may have been an interaction between prior recruitment and falling temperature that reduced growth rates. The rate of growth differed among habitats, but not in proportion to the densities established at settlement-as might be expected if preference for habitats conferring better growth had evolved. The growth of juvenile fish from different reefs within and between different regions of the Great Barrier Reef also showed some significant differences. In all analyses of variance, the residual natural variation accounted for most of the sums-of-squares, highlighting the great plasticity of fish growth.