Search

Somatic growth dynamics are an integrated response to environmental conditions. Hawksbill sea turtles (Eretmochelys imbricata) are long‐lived, major consumers in coral reef habitats that move over broad geographic areas (hundreds to thousands of kilometers). We evaluated spatio‐temporal effects on hawksbill growth dynamics over a 33‐yr period and 24 study sites throughout the West Atlantic and explored relationships between growth dynamics and climate indices. We compiled the largest ever data set on somatic growth rates for hawksbills – 3541 growth increments from 1980 to 2013. Using generalized additive mixed model analyses, we evaluated 10 covariates, including spatial and temporal variation, that could affect growth rates. Growth rates throughout the region responded similarly over space and time. The lack of a spatial effect or spatio‐temporal interaction and the very strong temporal effect reveal that growth rates in West Atlantic hawksbills are likely driven by region‐wide forces. Between 1997 and 2013, mean growth rates declined significantly and steadily by 18%. Regional climate indices have significant relationships with annual growth rates with 0‐ or 1‐yr lags: positive with the Multivariate El Niño Southern Oscillation Index (correlation = 0.99) and negative with Caribbean sea surface temperature (correlation = −0.85). Declines in growth rates between 1997 and 2013 throughout the West Atlantic most likely resulted from warming waters through indirect negative effects on foraging resources of hawksbills. These climatic influences are complex. With increasing temperatures, trajectories of decline of coral cover and availability in reef habitats of major prey species of hawksbills are not parallel. Knowledge of how choice of foraging habitats, prey selection, and prey abundance are affected by warming water temperatures is needed to understand how climate change will affect productivity of consumers that live in association with coral reefs.

Baseline information on abundance and growth patterns of green turtles was collected at Culebra, Puerto Rico from 1987 to 1989. A total of 167 individuals was captured, measured, tagged, and released. Twenty-five were recaptured 32 times for a recapture rate of 19%. Of 7 sampling areas, Mosquito Bay and Culebrita harbored the highest abundance of turtles with 2.16 and 2.04 caught per net set, re- spectively. Carapace length (CL) ranged from 24.6 to 75.3 cm, averaging 46.34 cm. The observed size-class composition was indicative of a juvenile population. A U.S. Virgin Islands age-size model suggested that turtles ranged in age from 2 to 14 yr old. Turtles grew at an annual rate of 5.08 cm (CL) with the highest growth rates recorded in the 40-50 cm CL interval. At the observed rates, turtles may spend 10 yr growing through the recorded CL range. Principal components analysis indicated that 99% of the variance was explained by the first or size component, with CL exhibiting the fastest relative growth rates of 4 mor- phometric variables. Shape components explained the remaining variance, with carapace width influencing most the general appearance of turtles. Our findings established that Culebra supports a juvenile green turtle population, and along with those of the U.S. Virgin Islands, confirmed the presence of developmental habitats and maturing populations through the eastern portion of the Puerto Rican Bank.

A model based on current knowledge of recruitment of settling juveniles of coral-reef fishes suggests that adult social groups far removed from their nearest neighbors can expect to attract larger numbers of juveniles than groups that are close to nearest neighbors. For protogynous fishes in which females change to males when intragroup, female-to-male sex ratios rise above threshold values, selection should favor individuals occupying groups that attract many juveniles. The model predicts that social groups should, in consequence, be regularly dispersed and that, in effect, groups compete with each other to attract juveniles. Dispersion of social groups was measured in two populations of the protogynous fish Anthias squamipinnis. The location of all groups were plotted on maps of the reef. A set of nearest-neighbor analyses applied to the data all showed significant departures of observed nearest-neighbor distances from randomness, in the direction of regularity. At both sites, neighboring groups were separated by much unoccupied space. In one population, the substrate consisted of discrete coral aggregates scattered over open sand bottom, while in the second population groups occupied a relatively continuous vertical reef face. Although regular dispersion could, in theory, result from regular distribution of food patches, current evidence does not favor this explanation. It is more likely that regular dispersion results either from the reproductive advantage of occupying groups that are highly attractive to juveniles, as seen in the model, or from limited perceptual and locomotor abilities of juveniles at the time of settlement.