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Tagging studies are often used to measure survival and growth in wild populations. However, issues such as low returns of tagged animals, tag loss, and handling mortality can affect the precision and accuracy of demographic estimates if not accounted for. We conducted a mark-recapture study to measure the survival and growth of juvenile and adult wavy turban snails Megastraea undosa. Our study highlights several methodological advances, including a method for estimating a single growth function by analyzing the joint changes in length and weight of tagged animals; a simple method for estimating rates of tag loss when some animals are double tagged; and a way to estimate handling mortality by comparing encounter histories of animals immediately after tagging and after several weeks in the field. Tag loss was moderate (≈15% over a 100 d period) and handling mortality was substantial during the fall (≈55%), but negligible during the spring. If we did not account for tag loss and handling mortality, our estimate of survival would have been severely underestimated (≈46% lower over a 100 d period). After accounting for such effects, our study revealed that survival probably increased sharply with body size, but survival did not differ among seasons. These snails are slow-growing, mature after approximately 6 yr, and can routinely grow to >10 yr old. There is an emerging fishery for this species, and because our results suggest that the oldest snails have a very high reproductive value, measures that protect these large individuals are likely to be beneficial for the resilience of these populations.

Examining vital rates helps clarify how environmental characteristics, biological resources and human activities affect population growth. Carapace lengths were gathered for 241 Kemp’s ridley Lepidochelys kempii sea turtles that were marked and recaptured (n = 23) between 2011 and 2019 at a foraging location in northwest Florida, USA. There was a strong correlation between length, width and weight of captured turtles. Mean ± SD size of all captured turtles was 36.6 ± 7.6 cm. Mean recapture interval was 499 ± 475.4 d. Straight-line carapace lengths at initial capture ranged from 20.6 to 53.3 cm. Growth rates from 0.21 to 12.44 cm yr-1 (mean 3.15 ± 2.64 cm) were documented and were greatest for turtles in the 20.0-29.9 cm size class. Growth rates from northwest Florida were slower than those reported from other sites in the Gulf of Mexico. These results indicate that Kemp’s ridleys recruit from oceanic habitat into coastal bays in northwest Florida, where they remain until they reach adulthood. However, some adult-sized turtles may continue to use the nearshore habitat. A gradient in growth rates in the Gulf of Mexico may occur from faster growth in the south to slower growth in the north. Fine-scale variations in resources and environmental conditions may drive regional differences in growth rates, and research on what drives these differences is needed.

Selective mortality is an important process influencing both the dynamics of marine populations and the evolution of their life histories. Despite a large and growing interest in measuring selective mortality, studies of marine species can face some serious methodological and analytical challenges. In particular, many studies of selection in marine environments use a cross- sectional approach in which fates of individuals are unknown but the distributions of trait values before and after a period of selective mortality may be compared. This approach is often used because many marine species have morphological structures (e.g. otoliths in fishes, statoliths in some invertebrates) that contain a permanent record of trait values. Although these structures often contain information on multiple, related traits, interpretation of selection measures has been limited because most studies of selection based on cross-sectional data consider selection 1 trait at a time, despite known problems with trait correlations. Here, we detail how cross-sectional data can be analyzed within a multivariate framework and provide a practical guide for conducting these types of analyses. We illustrate these methods by applying them to empirical studies of selective mortality on early life history traits in 2 species of reef fish. These examples demonstrate that analyzing selective mortality in a multivariate framework can vastly improve estimates of selection and yield new insight into how combinations of traits can interact to influence survival. Accompanying the paper are 2 R scripts that can be used to perform the calculations described here and assist with visualizing selection on multiple traits.

Marine reserves can directly replenish heavily fished species. However, communitywide effects of reserves are less clear. Marine reserves directly reduce fishing mortality rates, but through the restoration of apex predators, reserves may have strong indirect effects on non-target species. We explored the effects of a large, fully protected marine reserve in the Bahamas on the community of coral-reef fishes. We examined the effect of the reserve on fish biomass by comparing the density and size of all fishes on similar reefs located inside and outside the reserve. Total biomass of fishes was approximately 7× higher in reserve sites, where biomass was strongly concentrated in species of higher trophic levels. Analysis based on the relative magnitude of individual species’ responses indicated that, on average, the largest species increased in biomass within the reserve, intermediate-sized species decreased, and the smallest species exhibited variable responses. Species’ responses to the reserve were also examined by pooling species into 9 trophic categories using consumptive relationships, which provided corroborating results. Large piscivores (e.g. sharks, large groupers) were on average larger and more abundant inside the reserve. Mid-trophic-level groups (e.g. small piscivores) had higher average biomass outside of the reserve, where the number of species and biomass of large predators was lower. Finally, some low-trophic-level groups (e.g. planktivores) had higher biomass within the reserve, while others (e.g. small herbivores) did not respond strongly. Overall, these results suggest that marine reserves can substantially alter the composition and structure of reef fish communities.