The reef fish assemblage at Orpheus Island, Great Barrier Reef, was examined using visual censuses and the ichthyocide rotenone. Small 3.5 m 2 quantitative rotenone samples, using a fine-mesh net to enclose the site, were compared with visual-point censuses (prior to the placement of the net), random-point censuses and strip censuses. Furthermore, the fishes collected inside and outside the net were examined to determine the relative efficiency of enclosed versus open rotenone samples. Rotenone samples comprised 128 species in 28 families. Of these, only 49% of the species overlapped between the enclosed (inside net) and open (outside net) samples. Only 17.7% of the species in the enclosed rotenone sample were seen prior to collection. Rotenone samples reveal that visual censuses underestimated the abundance of small taxa. Overall, rotenone samples increased the estimated number of species by 40.4% and the total fish abundance by 50.1% (75.3% for fishes < 50 mm). Biomass increased by less than 1.0%. However, through relatively high energetic demands, high turnover rates and their role as potential prey, small fish taxa may play a greater role in reef processes than previously assumed. The limits of visual censusing techniques are highlighted, emphasising the value of small, enclosed, intensive rotenone samples for providing reliable quantitative samples of small taxa.

The 1998 global coral bleaching event was the largest recorded historical disturbance of coral reefs and resulted in extensive habitat loss. Annual censuses of reef fish community structure over a 12-year period spanning the bleaching event revealed a marked phase shift from a prebleach to postbleach assemblage. Surprisingly, we found that the bleaching event had no detectable effect on the abundance, diversity or species richness of a local cryptobenthic reef fish community. Furthermore, there is no evidence of regeneration even after 5-35 generations of these short-lived species. These results have significant implications for our understanding of the response of coral reef ecosystems to global warming and highlight the importance of selecting appropriate criteria for evaluating reef resilience.

The parrotfish Sparisoma viride is an abundant and ecologically important member of the tropical NW Atlantic reef fish fauna. Sagittal otoliths of 417 individuals were analysed to estimate age-based demographic variables at 4 localities (Lee Stocking Island, Barbados, Los Roques Archipelago and the San Blas Archipelago) spanning 14°of latitude. The sampling localities ranged from an area protected from trap-and net-based reef fisheries (Los Roques) to an area supporting a dense human population and sustained trapping and spearing for reef fishes including S. viride (Barbados). Examination of sectioned sagittal otoliths from each locality revealed regular increments in the sagittal matrix. A preliminary validation at San Blas was consistent with these increments being annual check marks. These increments provided estimates of age structure, maximum longevities and mortality rates for the 4 study populations of S. viride. Von Bertalanffy growth functions fitted to each size-at-age plot generated similar growth curves from 3 of these 4 localities. The exception was Lee Stocking, where fish grew faster and reached a substantially larger size than those from the other 3 localities. Further analysis of the growth curves demonstrated that the differences between Lee Stocking and the other localities were attributable to more rapid growth over the first 4 yr of life. Agebased growth curves derived from the Los Roques population were very similar to a size-based curve generated by an independent study on S. viride carried out in Bonaire, adjacent to Los Roques. Maximum longevities for all 4 of our populations varied from 7 to 9 yr. Mortality rates generated from catch curve analysis were also similar among localities and suggest that maximum life spans do not exceed 12 yr. This result differs from that obtained at Bonaire, where repeated censuses of tagged fish suggest 30 yr maximum longevity. Abundances of S. viride varied 3-fold among localities, being highest at Los Roques (protected from reef fishing), lowest at Barbados (high fishing) and Lee Stocking (low fishing). Thus our age-based study suggests that S. viride is a relatively short-lived fish with consistent demographic parameters over a range of localities, latitudes and fishing intensities.

The ocean surgeonfish Acanthurus bahianus is a common inhabitant of reefs throughout the west and central Atlantic. We examined geographic variation in its demography among 10 locations spanning 56°of latitude. These populations exhibit a great diversity of growth trajectories, as well as 3-fold variation in terminal size and maximum longevity. There are strongly contrasting patterns of habitat variation in demography at 2 sites: at Bermuda, fish settle inshore, grow to about asymptotic size and then, when 2 to 6 yr old, relocate permanently to outer reefs, where they can reach 32 yr. At Belize, fish settle and attain 10 yr on both inner and outer reefs, but grow faster and reach a ~50% greater asymptotic weight on inner reefs. Habitat differences in growth at Belize largely span the range of variation among NW Atlantic locations. A. bahianus exhibits the fastest growth known for an acanthurid, and the strongest spatial variation in demography known for a tropical reef-fish. Maximum age, adult survivorship, terminal size and absolute growth rate are inversely related to temperature. However, relative growth rate is not: in all populations a similar percentage of mean asymptotic standard length (L ∞ ) is achieved at 1, 2 and 3 yr, and then growth effectively ceases. Variation in longevity is related to temperature, and is largely independent of size. Variation in growth and size is related strongly to both habitat and temperature effects, and the rate of growth appears to set terminal size. High longevity at 3 isolated oceanic islands seems to reflect a temperature effect, rather than an island effect.