Calcification in many invertebrate species is predicted to decline due to ocean acidification. The potential effects of elevated CO₂ and reduced carbonate saturation state on other species, such as fish, are less well understood. Fish otoliths (earbones) are composed of aragonite, and thus, might be susceptible to either the reduced availability of carbonate ions in seawater at low pH, or to changes in extracellular concentrations of bicarbonate and carbonate ions caused by acid-base regulation in fish exposed to high <i>p</i>CO₂. We reared larvae of the clownfish <i>Amphiprion percula</i> from hatching to settlement at three pH_NBS and <i>p</i>CO₂ levels (control: ~pH 8.15 and 404 μatm CO₂; intermediate: pH 7.8 and 1050 μatm CO₂; extreme: pH 7.6 and 1721 μatm CO₂) to test the possible effects of ocean acidification on otolith development. There was no effect of the intermediate treatment (pH 7.8 and 1050 μatm CO₂) on otolith size, shape, symmetry between left and right otoliths, or otolith elemental chemistry, compared with controls. However, in the more extreme treatment (pH 7.6 and 1721 μatm CO₂) otolith area and maximum length were larger than controls, although no other traits were significantly affected. Our results support the hypothesis that pH regulation in the otolith endolymph can lead to increased precipitation of CaCO₃ in otoliths of larval fish exposed to elevated CO₂, as proposed by an earlier study, however, our results also show that sensitivity varies considerably among species. Importantly, our results suggest that otolith development in clownfishes is robust to even the more pessimistic changes in ocean chemistry predicted to occur by 2100

Life-history theory predicts that small species will exhibit short life-spans and fast growth rates; however, previous studies indicate that a positive relationship between size and maximum age may not be universally applicable to coral reef fishes. Here, we investigate the growth and life-span of 5 small species of coral reef goby (family Gobiidae): Istigobius goldmanni, Asterropteryx semipunctatus, Amblygobius bynoensis, Amblygobius phalaena and Valenciennea muralis. All 5 species were relatively short-lived, with the oldest individual sampled ranging from 11 to 16 mo depending on species and sex. Rapid growth occurred over much of the size range of all 5 species and, in contrast to most reef fishes, relatively little or no time was spent at an asymptotic size. Patterns of growth were best described by a Broken Stick model for I. goldmanni, and by either a Broken Stick model or the von Bertalanffy growth function for the other 4 species. Summer-growing individuals had higher growth rates than winter-growing individuals, but this did not affect the overall patterns of growth. Sex-specific differences in growth were evident for I. goldmanni and A. semipunctatus, with males growing faster and attaining a larger maximum size than females. In contrast, there was no significant difference in growth between male and female A. bynoensis, A. phalaena and V. muralis. This pattern may be related to interspecific differences in intensity of sexual selection, mating system, and reproductive behaviour. Overall, the patterns of growth and life-span of these 5 small species conformed to traditional concepts of life-history theory.

No abstract

No abstract