Marine reserves are increasingly recognized as having linked social and ecological dynamics. This study investigates how the ecological performance of 56 marine reserves throughout the Philippines, Caribbean, and Western Indian Ocean (WIO) is related to both reserve design features and the socioeconomic characteristics in associated coastal communities. Ecological performance was measured as fish biomass in the reserve relative to nearby areas. Of the socioeconomic variables considered, human population density and compliance with reserve rules had the strongest effects on fish biomass, but the effects of these variables were region specific. Relationships between population density and the reserve effect on fish biomass were negative in the Caribbean, positive in the WIO, and not detectable in the Philippines. Differing associations between population density and reserve effectiveness defy simple explanation but may depend on human migration to effective reserves, depletion of fish stocks outside reserves, or other social factors that change with population density. Higher levels of compliance reported by resource users was related to higher fish biomass in reserves compared with outside, but this relationship was only statistically significant in the Caribbean. A heuristic model based on correlations between social, cultural, political, economic, and other contextual conditions in 127 marine reserves showed that high levels of compliance with reserve rules were related to complex social interactions rather than simply to enforcement of reserve rules. Comparative research of this type is important for uncovering the complexities surrounding human dimensions of marine reserves and improving reserve management.coral reef | human-environment interactions | socioeconomic | social-ecological system | marine protected area H uman influences on marine ecosystems are pervasive (1) and strong (2-5). Marine reserves, which prohibit extractive activities such as fishing, are one of the key management measures used to mitigate anthropogenic impacts on marine systems. Marine reserves vary considerably in design, maintenance, and performance, in part because they are at the interface of complex social and ecological linkages. Social, economic, cultural, and political conditions can have profound influences on the ways that societies organize to use and manage resources, including the development, placement, and implementation of nature reserves (6). Ecologically, marine reserves often are isolated islands of low human use within larger areas of extensive and often intense resource extraction and habitat modification. The complexity of these social-ecological interactions may produce site-specific and surprising responses but may also be driven by predictable resource needs along gradients of human population and development (7).The success of marine reserves has both social and ecological dimensions, and recent multidisciplinary investigations are uncovering important roles for both (8-10). The empirical research that links ...

Profound ecological changes are occurring on coral reefs throughout the tropics, with marked coral cover losses and concomitant algal increases, particularly in the Caribbean region. Historical declines in the abundance of large Caribbean reef fishes likely reflect centuries of overexploitation. However, effects of drastic recent degradation of reef habitats on reef fish assemblages have yet to be established. By using meta-analysis, we analyzed time series of reef fish density obtained from 48 studies that include 318 reefs across the Caribbean and span the time period 1955-2007. Our analyses show that overall reef fish density has been declining significantly for more than a decade, at rates that are consistent across all subregions of the Caribbean basin (2.7% to 6.0% loss per year) and in three of six trophic groups. Changes in fish density over the past half-century are modest relative to concurrent changes in benthic cover on Caribbean reefs. However, the recent significant decline in overall fish abundance and its consistency across several trophic groups and among both fished and nonfished species indicate that Caribbean fishes have begun to respond negatively to habitat degradation.

A notable recent development in marine ecology has been the suggestion that the size of demersal populations is limited and that patterns in demersal abundance are determined by the settlement of pelagic larvae (recruitment). Here I examine some factors potentially limiting and determining population density in a small coral reef fish. An experimental study of the demography of juveniles of a small planktivorous damselfish, the humbug Dascyllus aruanus (Pomacentridae), was done at One Tree Reef, southern Great Barrier Reef, Australia. Recently settled fish were transplanted to replicate units of habitat at three lagoonal sites. The interactive effects of initial recruit density, the presence of adults, and supplemental feeding on the growth, survival, migration, and maturation of the recruits were examined over the following 10 mo. Migration was apparently rare and thus unimportant. Effects of the factors on the growth and survival of recruits were complex. Survival of recruits was generally inversely related to their density but enhanced in the presence of adults. Average survival also varied among locations. Mean growth was generally depressed at high recruit densities and in the presence of adults but was enhanced by supplemental feeding. Maturation was related to size and so was influenced by effects on growth. The results suggest that regulatory interactions and shortages of food may limit the size of adult populations via their effect on growth rates. Effects of the factors on survival were slight. Total abundance may thus be limited primarily by recruitment unless effects on growth are ultimately translated to effects on demersal mortality. As a result of the effects on survival, there was some modification of the initial pattern of recruit abundance. The importance of these effects in determining patterns of abundance in unmanipulated populations depends on variation in recruitment at similar scales. The number of recruits entering the adult population under different treatments was highly modified from the pattern of initial recruit density. The number of recruits that became mature by the end of the experiment was totally unrelated to their initial density. In addition, that number was reduced in the presence of adults, and was limited by the availability of food. The results suggest that complex effects of these factors on juvenile demography can modify recruitment patterns at small spatial scales. They also suggest that these factors may have different effects on the adult and total demersal populations. In general terms, both recruitment and postrecruitment processes influence patterns in abundance.

For species with metapopulation structures, variation in abundance among patches can arise from variation in the input rate of colonists. For reef fishes, variability in larval supply frequently is invoked as a major determinant of spatial patterns. We examined the extent to which spatial variation in the amount of suitable habitat predicted variation in the abundance of the damselfish Dascyllus aruanus, an abundant planktivore that occupies live, branched coral throughout the Indo-Pacific. Reef surveys established that size, branching structure and location (proximity to sand) of the coral colonies together determined the "suitability" of microhabitats for different ontogenetic stages of D. aruanus. Once these criteria were known, patterns of habitat use were quantified within lagoons of five Pacific islands. Availability of suitable habitat generally was an excellent predictor of density, and patterns were qualitatively consistent at several spatial scales, including among different lagoons on the same island, among different islands and between the central (French Polynesia and Rarotonga) and western (Great Barrier Reef, Australia) South Pacific. A field experiment that varied the amount of suitable coral among local plots indicated that habitat for settlers accounted for almost all of the spatial variation in the number of D. aruanus that settled at that location, suggesting that spatial patterns of abundance can be established at settlement without spatial variation in larval supply. Surveys of four other species of reef-associated fish revealed that a substantial fraction of their spatial variation in density also was explained by availability of suitable reef habitat, suggesting that habitat may be a prevalent determinant of spatial patterns. The results underscore the critical need to identify accurately the resource requirements of different species and life stages when evaluating causes of spatial variation in abundance of reef fishes.