We studied the influence ofpiscivorous fishes and prey refuges on assemblages of fishes occupying 52 model reefs in a large seagrass bed off St. Thomas, U.S. Virgin Islands. We conducted three experiments: two involving 6 reefs each, lasting 2 and 5 yr, and one involving 40 reefs, lasting 1 yr. Each experiment included replicate reefs in various combinations of five structural treatments: holeless controls, 12 and 24 small holes, and 12 and 24 large holes. Tagging studies indicated that the reefs were sufficiently isolated from each other to comprise statistically independent replicates, and that resident piscivores occupied home reefs. We observed 97 species on or near the reefs, representing all major foraging guilds, and each holed reef supported hundreds of individuals. We examined four categories offish: (1) large reef associates (too large for the small holes; most of these fish were both predators on smaller fish and prey for larger transient piscivores), (2) moray eels (piscivores that could fit into the small holes), (3) small reef associates (potential prey that could fit into the small holes), and (4) juvenile grunts (potential prey that sporadically were extremely abundant).We tested five a priori predictions of the general hypothesis that predation is an important process structuring reef-fish assemblages. The first two predictions dealt with the role of prey refuges. First, if reef holes function as prey refuges, then prey fish should be most abundant on reefs providing holes near their body diameters, because such holes would make the prey fish safest from predation. Seven of eight experimental comparisons supported this prediction, and five of them were statistically significant. Second, if refuge availability limits prey abundance, then prey fish should be more abundant on reefs with 12 holes than those with no holes, and should be more abundant on reefs with 24 holes than those with 12 holes. The first part of this prediction was verified by all nine experimental comparisons, seven of which were statistically significant. However, there were no strong differences between 12-hole and 24-hole reefs. Thus, between 0 and 12 holes per reef, holes limited local prey populations; between 12 and 24 holes per reef, the number of holes was not limiting. Several lines of evidence suggested that the latter pattern was due to temporary saturation of the study area with refuges when we added 40 reefs to 12 existing reefs.The remaining three predictions dealt directly with the community-level role of predation. First, predators should affect local prey abundance either chronically, in which case a negative relationship among reefs is predicted between the average abundances of predators and prey, or sporadically, in which case a negative relationship is predicted between the abundance of predators and the maximum number of co-occurring prey ever observed at each predator abundance. The former prediction was falsified, whereas the latter was verified. Observations of extreme type III survivorship of recruit coh...

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.

Acceptance of marine protected areas (MPAs) as fishery and conservation tools has been hampered by lack of direct evidence that MPAs successfully seed unprotected areas with larvae of targeted species. For the first time, we present direct evidence of large-scale population connectivity within an existing and effective network of MPAs. A new parentage analysis identified four parent-offspring pairs from a large, exploited population of the coral-reef fish Zebrasoma flavescens in Hawai'i, revealing larval dispersal distances ranging from 15 to 184 km. In two cases, successful dispersal was from an MPA to unprotected sites. Given high adult abundances, the documentation of any parent-offspring pairs demonstrates that ecologically-relevant larval connectivity between reefs is substantial. All offspring settled at sites to the north of where they were spawned. Satellite altimetry and oceanographic models from relevant time periods indicated a cyclonic eddy that created prevailing northward currents between sites where parents and offspring were found. These findings empirically demonstrate the effectiveness of MPAs as useful conservation and management tools and further highlight the importance of coupling oceanographic, genetic, and ecological data to predict, validate and quantify larval connectivity among marine populations.

An expedition to Salas y Gómez and Easter islands was conducted to develop a comprehensive baseline of the nearshore marine ecosystem, to survey seamounts of the recently created Motu Motiro Hiva Marine Park (MMHMP) – a no‐take marine reserve of 150 000 km2 – and to compare these results with Easter Island where the marine ecosystem is similar but has no marine protection.Live coral cover was surprisingly high at both Easter Island (53%) and Salas y Gómez (44%), especially considering their sub‐tropical location, high wave energy environments, and geographic isolation.Endemic and regionally‐endemic species comprised 77% of the fish abundance at Easter Island and 73% at Salas y Gómez. Fish biomass at Salas y Gómez was relatively high (1.2 t ha‐1) and included a large proportion of apex predators (43%), whereas at Easter Island it was almost three times lower (0.45 t ha‐1) with large predators accounting for less than 2% of the biomass, despite good habitat quality.The large cohort of small sharks and the absence of larger sharks at Salas y Gómez suggest mesopredator release consistent with recent shark fishing. The fish fauna at the seamounts between Easter Island and Salas y Gómez, outside of MMHMP, harboured 46% endemic species, including a new species of damselfish (Chromis sp. nov.) and probably a new species of Chimaera (Hydrolagus). Numerous seamounts adjacent to Salas y Gómez are currently not included in the MMHMP.This expedition highlights the high biodiversity value of this remote part of the Pacific owing to the uniqueness (endemicity) of the fauna, large apex predator biomass, and geographic isolation.Copyright © 2013 John Wiley & Sons, Ltd.

Lionfish (Pterois volitans and P. miles) have become a major concern in the western Atlantic and Caribbean since their introduction in the 1980s. Invasive lionfish can reach very high population densities on coral reefs in their invaded range, yet there are few data from their native range in the Indo-Pacific for comparison. We compiled data on the geographical distribution and density of Indo-Pacific lionfishes in their native ranges from published and unpublished underwater visual censuses and field collections. We found that lionfish in their native Indo-Pacific range are unevenly distributed, with higher densities in the Indian Ocean than in the Pacific. Lionfish densities increase significantly with increasing latitude, and are significantly higher in continental areas than around islands. In the Indo-Pacific, lionfishes are found not only on reefs but also on soft bottoms and in nearshore habitats such as seagrass beds and mangroves, and near estuaries. Native lionfish can be found at depths greater than 75 m. Because lionfish can be cryptic and secretive, we estimate that only ~1/8 of Indo-Pacific lionfishes are detected during general underwater visual censuses. In the Pacific Ocean, the relative abundance of lionfish in the catch of reef-fish larvae is of the same order of magnitude as the relative abundance of adult lionfish within reef fish assemblages. Overall the observed densities of lionfishes in the Indo-Pacific are much lower (max. 26.3 fish ha -1 ) than the densities reported in their invaded Atlantic range (max. 400 fish ha -1 ). We found no effects of fishing or pollution on the densities of lionfishes.