Comparative demography of commercially important species of coral grouper,Plectropomus leopardus and P. laevis,from Australia's great barrier reef and Coral Sea marine parks

Understanding the spatial and environmental variation in demographic processes of fisheries target species, such as coral grouper (Genus: Plectropomus), is important for establishing effective management and conservation strategies. Herein we compare the demography of Plectropomus leopardus and P. laevis between Australia's Great Barrier Reef Marine Park (GBRMP), which has been subject to sustained and extensive fishing pressure, and the oceanic atolls of Australia's Coral Sea Marine Park (CSMP), where there is very limited fishing for reef fishes. Coral grouper length-at-age data from contemporary and historical otolith collections across 9.4 degrees of latitude showed little difference in lifetime growth between GBRMP and CSMP regions. Plectropomus laevis populations in GBRMP reefs had significantly higher rates of total mortality than populations in the CSMP. Mean maximum lengths and mean maximum ages of P. laevis were also smaller in the GBRMP than in the CSMP, even when considering populations sampled within GBRMP no-take marine reserves (NTMRs). Plectropomus leopardus, individuals were on average smaller on fished reefs than NTMRs in the GBRMP, but all other aspects of demography were broadly similar between regions despite the negligible levels of fishing pressure in the CSMP. Similarities between regions in growth profiles and length-at-age comparisons of P. laevis and P. leopardus suggest that the environmental differences between the CSMP and the GBRMP may not have significant impacts on lifetime growth. Our results show that fishing may have influenced the demography of coral grouper on the GBR, particularly for the slower growing and longer lived species, P. laevis.     

Partially protected areas as a management tool on inshore reefs

Partially Protected Areas (PPAs) are a widely-used management tool, yet comparatively little is known about their effectiveness compared to more commonly studied No-Take Marine Reserves (NTMRs). Here, we examine the efficacy of two kinds of PPAs (with and without spearfishing) within the Great Barrier Reef Marine Park (GBRMP) that are subject to a range of fishing limitations, and assess their utility as a marine park zoning and fisheries management tool. Fish abundance, size, and habitat composition were compared inside PPAs and NTMRs on inshore reefs of the central GBR. Fish abundances were lower inside PPAs relative to adjacent NTMRs for primary fishing targets, with no detectable effects for secondary targets and non-targets, or for species richness. Fish assemblages differed amongst zones, but these variations were minor compared to regional variations in species composition. Partially Protected Areas supported 46%–69% of the relative abundance of total primary targets compared to adjacent NTMRs, with no evident increase in abundance in zones where spearfishing was prohibited. There were no reductions in the size of two key target species: coral trout (Plectropomus spp.) and stripey snapper (Lutjanus carponotatus) inside PPAs, and only stripey snapper had significant reductions in abundance inside PPAs compared to NTMRS. Habitat and biophysical characteristics (especially topographic complexity) were strong drivers of fish abundance, but the relative influence of zone was greater for target species compared to non-targets. This study provides novel data on PPAs and highlights their utility as a spatial management tool in contributing to conservation and fisheries management goals.

     

Development of reproductive potential in protogynous coral reef fishes within Philippine no-take marine reserves

Empirical evidence for increases in the reproductive potential (egg output per unit area) of coral reef fish in no-take marine reserves (NTMRs) is sparse. Here, we inferred the development of reproductive potential in two species of protogynous reef fishes, Chlorurus bleekeri (Labridae: Scarinae) and Cephalopholis argus (Epinephelidae), inside and outside of Philippine NTMRs. We estimated key reproductive parameters and applied these to species-specific density and length data from 17 NTMRs (durations of protection 0–11 years) and paired fished sites (controls) in a space-for-time substitution approach. For C. argus, we also used density and length data collected almost annually over 29 years from a NTMR and an adjacent control at Apo Island. The results suggest that C. bleekeri can develop 6.0 times greater reproductive potential in NTMRs than controls after 11 years of protection, equivalent to approximately 582,000 more eggs produced 500 m⁻² inside NTMRs. Enhancement of reproductive potential in C. argus was not evident after 11 years in the space-for-time substitution. At Apo Island NTMR, reproductive potential of C. argus increased approximately 6-fold over 29 years but NTMR/control ratios in reproductive potential decreased through time (from 3.2 to 2.4), probably due to spillover of C. argus from the NTMR to the control. C. argus was estimated to produce approximately 113,000 more eggs 500 m⁻² inside Apo Island NTMR at the 29th year of protection. Ratios of reproductive potential between NTMR and controls in C. bleekeri and C. argus were often greater than corresponding ratios in density or biomass. The study underscores the importance of species-specific reproductive life history traits that drive variation in the development of larval fish subsidies that originate from NTMRs.     

Reserves as tools for alleviating impacts of marine disease

Marine protected areas can prevent over-exploitation, but their effect on marine diseases is less clear. We examined how marine reserves can reduce diseases affecting reef-building corals following acute and chronic disturbances. One year after a severe tropical cyclone, corals inside reserves had sevenfold lower levels of disease than those in non-reserves. Similarly, disease prevalence was threefold lower on reserve reefs following chronic exposure to terrestrial run-off from a degraded river catchment, when exposure duration was below the long-term site average. Examination of 35 predictor variables indicated that lower levels of derelict fishing line and injured corals inside reserves were correlated with lower levels of coral disease in both case studies, signifying that successful disease mitigation occurs when activities that damage reefs are restricted. Conversely, reserves were ineffective in moderating disease when sites were exposed to higher than average levels of run-off, demonstrating that reductions in water quality undermine resilience afforded by reserve protection. In addition to implementing protected areas, we highlight that disease management efforts should also target improving water quality and limiting anthropogenic activities that cause injury.     

Effect of bêche-de-mer fishing on densities and size structure of Holothuria nobilis (Echinodermata: Holothuroidea) populations on the Great Barrier Reef

Decreasing catch rates for Holothuria nobilis (black teatfish) on the Great Barrier Reef (GBR) prompted management agencies to close the fishery for this species in October 1999. At the same time, we surveyed densities and size structure of H. nobilis populations in the main area fished on the GBR. Densities of H. nobilis on four reefs protected from fishing (approximately 20 ind. ha^-1) were about four times higher than those on 16 reefs open to fishing (approximately 5 ind. ha^-1). Each of four other reefs had been divided into an area protected from fishing and an open area. On the largest of these reefs (ca. 28 km long), densities of H. nobilis were nearly five times higher in the protected area compared to the area open to fishing. On three smaller reefs (<11 km long), however, densities were not significantly different between the open and protected area, and were similar to that on reefs completely open to fishing. The average weight of individuals was significantly reduced on fished reefs (1,763 g) compared to closed reefs (2,200 g). Thus, bêche-de-mer fishing led to a strong reduction of density and biomass of H. nobilis. The division of smaller reefs into open and closed zones appears not to provide sufficient protection, but reefs that are completely closed to fishing appear to provide some degree of protection. There were some indications that proximity to tourist attractions may enhance the effect of protection.     

Impacts and Recovery from Severe Tropical Cyclone Yasi on the Great Barrier Reef

Full recovery of coral reefs from tropical cyclone (TC) damage can take decades, making cyclones a major driver of habitat condition where they occur regularly. Since 1985, 44 TCs generated gale force winds (≥17 metres/second) within the Great Barrier Reef Marine Park (GBRMP). Of the hurricane strength TCs (≥H1—Saffir Simpson scale; ≥ category 3 Australian scale), TC Yasi (February, 2011) was the largest. In the weeks after TC Yasi crossed the GBRMP, participating researchers, managers and rangers assessed the extent and severity of reef damage via 841 Reef Health and Impact Surveys at 70 reefs. Records were scaled into five damage levels representing increasingly widespread colony-level damage (1, 2, 3) and reef structural damage (4, 5). Average damage severity was significantly affected by direction (north vs south of the cyclone track), reef shelf position (mid-shelf vs outer-shelf) and habitat type. More outer-shelf reefs suffered structural damage than mid-shelf reefs within 150 km of the track. Structural damage spanned a greater latitudinal range for mid-shelf reefs than outer-shelf reefs (400 vs 300 km). Structural damage was patchily distributed at all distances, but more so as distance from the track increased. Damage extended much further from the track than during other recent intense cyclones that had smaller circulation sizes. Just over 15% (3,834 km²) of the total reef area of the GBRMP is estimated to have sustained some level of coral damage, with ~4% (949 km²) sustaining a degree of structural damage. TC Yasi likely caused the greatest loss of coral cover on the GBR in a 24-hour period since 1985. Severely impacted reefs have started to recover; coral cover increased an average of 4% between 2011 and 2013 at re-surveyed reefs. The in situ assessment of impacts described here is the largest in scale ever conducted on the Great Barrier Reef following a reef health disturbance.     

No-take reserves protect coral reefs from predatory starfish

The crown-of-thorns starfish, Acanthaster planci, is a predator of corals that is a major management issue on coral reefs [1]. It occurs throughout the Indo–Pacific and shows boom–bust population dynamics with low background densities and intermittent outbreaks. Three waves of population outbreaks have affected Australia's Great Barrier Reef (GBR) since the 1960s. The waves of outbreaks appear to start 15°S [2] and progress southward through the central GBR (Figure 1A), causing major losses of living coral on many reefs across a large area and dwarfing losses from other disturbances such as storms or coral bleaching over the same period [3]. Humans can potentially influence starfish population dynamics by exploiting predators, though evidence to date is circumstantial. Extensive surveys in the GBR Marine Park (GBRMP) show that protection from fishing affects the frequency of outbreaks: the relative frequency of outbreaks on reefs that were open to fishing was 3.75 times higher than that on no-take reefs in the mid-shelf region of the GBR, where most outbreaks occur, and seven times greater on open reefs if all reefs were included. Although exploited fishes are unlikely to prey on starfish directly, trophic cascades could favour invertebrates that prey on juvenile starfish.     

Rapid increase in fish numbers follows creation of world's largest marine reserve network

No-take marine reserves (NTMRs) are much advocated as a solution to managing marine ecosystems, protecting exploited species and restoring natural states of biodiversity [1,2]. Increasingly, it is becoming clear that effective marine conservation and management at ecosystem and regional scales requires extensive networks of NTMRs [1,2]. The world's largest network of such reserves was established on Australia's Great Barrier Reef (GBR) in 2004. Closing such a large area to all fishing has been socially and politically controversial, making it imperative that the effectiveness of this new reserve network be assessed. Here we report evidence, first, that the densities of the major target species of the GBR reef line fisheries were significantly higher in the new NTMRs, compared with fished sites, in just two years; and second, that the positive differences were consistent for multiple marine reserves over an unprecedented spatial scale (>1,000 km).     

Kenyan coral reef lagoon fish: effects of fishing,substrate complexity,and sea urchins

Population density, number of species, diversity, and species-area relationships of fish species in eight common coral reef-associated families were studied in three marine parks receiving total protection from fishing, four sites with unregulated fishing, and one reef which recently received protection from fishing (referred to as a transition reef). Data on coral cover, reef topographic complexity, and sea urchin abundance were collected and correlated with fish abundance and species richness. The most striking result of this survey is a consistent and large reduction in the population density and species richness of 5 families (surgeonfish, triggerfish, butterflyfish, angelfish, and parrotfish). Poor recovery of parrotfish in the transition reef, relative to other fish families, is interpreted as evidence for competitive exclusion of parrotfish by sea urchins. Reef substrate complexity is significantly associated with fish abundance and diversity, but data suggest different responses for protected versus fished reefs, protected reefs having higher species richness and numbers of individuals than unprotected reefs for the same reef complexity. Sea urchin abundance is negatively associated with numbers of fish and fish species but the interrelationship between sea urchins, substrate complexity, coral cover, and management make it difficult to attribute a set percent of variance to each factor-although fishing versus no fishing appears to be the strongest variable in predicting numbers of individuals and species of fish, and their community similarity. Localized species extirpation is evident for many species on fished reefs (for the sampled area of 1.0 ha). Fifty-two of 110 species found on protected reefs were not found on unprotected reefs.     

Drivers of region-wide declines in architectural complexity on Caribbean reefs

Severe declines in the cover of live hard coral on reefs have been reported worldwide, and in the Caribbean region, the architectural complexity of coral reefs has also declined markedly. While the drivers of coral cover loss are relatively well understood, little is known about the drivers of regional-scale declines in architectural complexity. We have used a dataset of 49 time series reporting reef architectural complexity to explore the effect of hurricanes, coral bleaching and fishing on Caribbean-wide annual rates of change in reef complexity. Hurricane impacts greatly influence reef complexity, with the most rapid rates of decline in complexity occurring at sites impacted during their survey period, and with lower rates of loss occurring at unimpacted sites. Reef architectural complexity did not change significantly following mass bleaching events (in a time frame of <5 years) or positive thermal anomalies. Although the rates of change in architectural complexity were similar in and out of marine protected areas (MPAs), significant declines in complexity were observed inside but not outside of MPAs, possibly because reductions in fishing can lead to increased bioerosion by herbivores within MPAs. Our findings suggest that major drivers of coral mortality, such as coral bleaching, do not influence reef architectural complexity in the short term (<5 years). Instead, direct physical impacts and reef bioerosion appear to be important drivers of the widespread loss of architecturally complex reefs in the Caribbean.     

Coral reefs in the Southern Barents Sea: habitat description and the effects of bottom fishing

Fifteen Lophelia reefs from offshore to coastal areas off northern Norway were studied using video. Health status of the coral habitat (degree of physical impact, % cover of living tissue, colony size), occurrence of trawl marks and lost fishing gear, height of coral colonies and associated fauna were analysed from 44 video-lines. Fishing impact was more frequent on the offshore reefs (36.5% of the observed areas) than those in the coastal reefs (0.6%). The most visible effects of fishing were broken and displaced coral colonies. At some sites only small scattered fragments of live corals were observed, indicating recent impact. The mean colony height of Lophelia and gorgonian corals at impacted sites was around half the size of those at non-impacted sites. Both species richness and abundance was higher at non-impacted coral habitats compared to impacted. The actinarian Protanthea simplex and unidentified brittlestars were the only taxa with higher abundance on impacted compared with non-impacted habitats. The reefs at the offshore location were protected against bottom trawling in 2009 through the establishment of a marine protected area (MPA), but a general ban against trawling on known coral reefs had already been implemented in 1999. In the MPA, signs of regrowth were observed. Most of the observed damage probably occurred over 10 years earlier. Results show that live and non-impacted cold water coral reefs have an important ecological function by enhancing the local biodiversity and fish abundance. Preventing further damage to impacted reefs may lead to full recovery within a few decades.     

Regional versus latitudinal variation in the life-history traits and demographic rates of a reef fish,Centropyge bispinosa,in the Coral Sea and Great Barrier Reef Marine Parks,Australia

Environmental temperature is an important determinant of physiological processes and life histories in ectotherms. Over latitudinal scales, variation in temperature has been linked to changes in life-history traits and demographic rates, with growth and mortality rates generally being greatest at low latitudes, and longevity and maximum length being greater at higher latitudes. Using the two-spined angelfish, Centropyge bispinosa, as our focal species, we compared growth patterns, growth rates, longevity, mortality, asymptotic length and maximum length across 22 reefs that span 13° of latitude within the Great Barrier Reef Marine Park (GBRMP) and the Coral Sea Marine Park (CSMP), Australia. We found no predictable latitudinal variation in mortality rates, growth patterns, growth rates, asymptotic or maximum length of C. bispinosa at regional to biogeographic scales. However, C. bispinosa consistently exhibited reduced longevity at lower, warmer latitudes within the CSMP. The greatest differences in mean maximum length of C. bispinosa were between continental (GBRMP) and oceanic (central CSMP) reefs of similar latitude, with individuals being larger on average on continental versus oceanic reefs. The lack of predictable life-history and demographic variation in C. bispinosa across a 13° latitudinal gradient within the CSMP, coupled with differences in mean maximum length between continental and oceanic reefs at similar latitudes, suggest that local environmental conditions have a greater influence than environmental temperature on the demographic rates and life-history traits of C. bispinosa.     

Effects of Spearfishing on Reef Fish Populations in a Multi-Use Conservation Area

Although spearfishing is a popular method of capturing fish, its ecological effects on fish populations are poorly understood, which makes it difficult to assess the legitimacy and desirability of spearfishing in multi-use marine reserves. Recent management changes within the Great Barrier Reef Marine Park (GBRMP) fortuitously created a unique scenario by which to quantify the effects of spearfishing on fish populations. As such, we employed underwater visual surveys and a before-after-control-impact experimental design to investigate the effects of spearfishing on the density and size structure of target and non-target fishes in a multi-use conservation park zone (CPZ) within the GBRMP. Three years after spearfishing was first allowed in the CPZ, there was a 54% reduction in density and a 27% reduction in mean size of coral trout (Plectropomus spp.), the primary target species. These changes were attributed to spearfishing because benthic habitat characteristics and the density of non-target fishes were stable through time, and the density and mean size of coral trout in a nearby control zone (where spearfishing was prohibited) remained unchanged. We conclude that spearfishing, like other forms of fishing, can have rapid and substantial negative effects on target fish populations. Careful management of spearfishing is therefore needed to ensure that conservation obligations are achieved and that fishery resources are harvested sustainably. This is particularly important both for the GBRMP, due to its extraordinarily high conservation value and world heritage status, and for tropical island nations where people depend on spearfishing for food and income. To minimize the effects of spearfishing on target species and to enhance protection of functionally important fishes (herbivores), we recommend that fishery managers adjust output controls such as size- and catch-limits, rather than prohibit spearfishing altogether. This will preserve the cultural and social importance of spearfishing in coastal communities where it is practised.     

Abrolhos bank reef health evaluated by means of water quality, microbial diversity, benthic cover, and fish biomass data

The health of the coral reefs of the Abrolhos Bank (Southwestern Atlantic) was characterized with a holistic approach using measurements of four ecosystem components: (i) inorganic and organic nutrient concentrations, [1] fish biomass, [1] macroalgal and coral cover and (iv) microbial community composition and abundance. The possible benefits of protection from fishing were particularly evaluated by comparing sites with varying levels of protection. Two reefs within the well-enforced no-take area of the National Marine Park of Abrolhos (Parcel dos Abrolhos and California) were compared with two unprotected coastal reefs (Sebasti?o Gomes and Pedra de Leste) and one legally protected but poorly enforced coastal reef (the "paper park" of Timbebas Reef). The fish biomass was lower and the fleshy macroalgal cover was higher in the unprotected reefs compared with the protected areas. The unprotected and protected reefs had similar seawater chemistry. Lower vibrio CFU counts were observed in the fully protected area of California Reef. Metagenome analysis showed that the unprotected reefs had a higher abundance of archaeal and viral sequences and more bacterial pathogens, while the protected reefs had a higher abundance of genes related to photosynthesis. Similar to other reef systems in the world, there was evidence that reductions in the biomass of herbivorous fishes and the consequent increase in macroalgal cover in the Abrolhos Bank may be affecting microbial diversity and abundance. Through the integration of different types of ecological data, the present study showed that protection from fishing may lead to greater reef health. The data presented herein suggest that protected coral reefs have higher microbial diversity, with the most degraded reef (Sebasti?o Gomes) showing a marked reduction in microbial species richness. It is concluded that ecological conditions in unprotected reefs may promote the growth and rapid evolution of opportunistic microbial pathogens.     

Parrotfish Size: A Simple yet Useful Alternative Indicator of Fishing Effects on Caribbean Reefs?

There is great need to identify simple yet reliable indicators of fishing effects within the multi-species, multi-gear, data-poor fisheries of the Caribbean. Here, we investigate links between fishing pressure and three simple fish metrics, i.e. average fish weight (an estimate of average individual fish size), fish density and fish biomass, derived from (1) the parrotfish family, a ubiquitous herbivore family across the Caribbean, and (2) three fish groups of “commercial” carnivores including snappers and groupers, which are widely-used as indicators of fishing effects. We hypothesize that, because most Caribbean reefs are being heavily fished, fish metrics derived from the less vulnerable parrotfish group would exhibit stronger relationships with fishing pressure on today’s Caribbean reefs than those derived from the highly vulnerable commercial fish groups. We used data from 348 Atlantic and Gulf Rapid Reef Assessment (AGRRA) reef-surveys across the Caribbean to assess relationships between two independent indices of fishing pressure (one derived from human population density data, the other from open to fishing versus protected status) and the three fish metrics derived from the four aforementioned fish groups. We found that, although two fish metrics, average parrotfish weight and combined biomass of selected commercial species, were consistently negatively linked to the indices of fishing pressure across the Caribbean, the parrotfish metric consistently outranked the latter in the strength of the relationship, thus supporting our hypothesis. Overall, our study highlights that (assemblage-level) average parrotfish size might be a useful alternative indicator of fishing effects over the typical conditions of most Caribbean shallow reefs: moderate-to-heavy levels of fishing and low abundance of highly valued commercial species.     

Opening of an MPA to fishing: Natural variations in the structure of a coral reef fish assemblage obscure changes due to fishing

Marine Protected Areas (MPAs) are known to enhance diversity, density and biomass of coral reef fishes and to modify the size and trophic structures of these fish assemblages. Opening to fishing has the opposite effects, but on a much shorter time scale. The present study compares the evolution of the fish assemblages of two adjacent reef zones, both initially MPAs, one of them being afterwards opened to fishing. The study was conducted on Aboré Reef, a New Caledonian barrier reef (SW Pacific) which constituted a 148 km² marine protected area, of which 69 km² are within the lagoon. Two surveys of a coral reef fish assemblage, using underwater visual censuses, were performed, the first one was conducted in July 1993 following 5 years of protection from fishing, the second one was conducted in July 1995; part of the reef having been opened to fishing activity in September 1993. This study examined the effects of two factors on these fish communities: time (1993 vs. 1995) and zone (reefs protected from fishing vs. unprotected reefs); the interaction of these two factors indicating an effect of either protection or opening to fishing. Diversity (species/transect), density and biomass were tested for all species together (377 species), then according to diet, size and commercial use. There was a significant decrease over time of most values in both fished and unfished areas, the decrease being greater in the zone opened to fishing. The magnitude of decrease over time was within the range of known time variations from other studies in New Caledonia and other Pacific locations. However, this decrease was so large that it prevented the detection of effects linked to protection. Only some minor effects could be detected for 16 species with no specific pattern according to diet, size or use. The density and biomass of species of low commercial value were also affected by opening to fishing. Relative changes in diversity could be better detected than relative changes in density or biomass. This study demonstrates that on a short-term basis (2 years), natural variations can be of larger magnitude than changes that may be induced by management options, especially when fishing pressure is not very high.     

Long-term change in coral cover and the effectiveness of marine protected areas in the Philippines: a meta-analysis

Although coral declines have been reported from major reefs of the world, region-specific trends still remain unclear, particularly in areas with high diversity such as the Philippines. We assessed the temporal patterns of the magnitude and trajectory of coral cover change in the Philippines using survey data collected from 317 sites. We examined the rate of change in coral cover in relation to time, effects of bleaching and protection against fishing and assessed the efficacy of marine protected areas (MPAs) using meta-analysis. Results showed an overall increase in coral cover in the Philippines from 1981 to 2010. Protection from fishing contributed to the overall increase in the mean annual rate of change as the coral cover significantly increased within MPAs than outside. The significant differences in the rate of coral cover change through time were influenced by chronic anthropogenic stresses, coinciding with the timing of thermal stress and the establishment of MPAs. The rate of change in coral cover was independent of the level of protection and the age and size of MPA.     

Effects of region,demography, and protection from fishing on batch fecundity of common coral trout (Plectropomus leopardus)

Batch fecundity of female Plectropomus leopardus, a coral reef fish targeted by commercial and recreational fishing, was compared between reefs open to fishing and reefs within no-take marine reserves within three regions of the Great Barrier Reef (GBR), Australia. Length, weight, and age had positive effects on batch fecundity of spawners from northern and central reefs but negligible effects on spawners from southern reefs. Females were least fecund for a given length, weight, and age in the southern GBR. Batch fecundity of a 500-mm fork length female was 430 % greater on central reefs and 207 % greater on northern reefs than on southern reefs. The effects of length and age on batch fecundity did not differ significantly between reserve and fished reefs in any region, but weight-specific fecundity was 100 % greater for large 2.0 kg females on reserve reefs compared with fished reefs in the central GBR. We hypothesize that regional variation in batch fecundity is likely driven by water temperature and prey availability. Significant regional variation in batch fecundity highlights the need for understanding spatial variation in reproductive output where single conservation or fishery management strategies cover large, potentially diverse, spatial scales.     

Global assessment of the status of coral reef herbivorous fishes: evidence for fishing effects

On coral reefs, herbivorous fishes consume benthic primary producers and regulate competition between fleshy algae and reef-building corals. Many of these species are also important fishery targets, yet little is known about their global status. Using a large-scale synthesis of peer-reviewed and unpublished data, we examine variability in abundance and biomass of herbivorous reef fishes and explore evidence for fishing impacts globally and within regions. We show that biomass is more than twice as high in locations not accessible to fisheries relative to fisheries-accessible locations. Although there are large biogeographic differences in total biomass, the effects of fishing are consistent in nearly all regions. We also show that exposure to fishing alters the structure of the herbivore community by disproportionately reducing biomass of large-bodied functional groups (scraper/excavators, browsers, grazer/detritivores), while increasing biomass and abundance of territorial algal-farming damselfishes (Pomacentridae). The browser functional group that consumes macroalgae and can help to prevent coral–macroalgal phase shifts appears to be most susceptible to fishing. This fishing down the herbivore guild probably alters the effectiveness of these fishes in regulating algal abundance on reefs. Finally, data from remote and unfished locations provide important baselines for setting management and conservation targets for this important group of fishes.     

Effects of a Marine Reserve on Recruitment of Grunts (Pisces: Haemulidae) at Barbados, West Indies

The effects of a non-extractive marine reserve on the recruitment dynamics of haemulid fishes and their predators on Barbados coral reefs were studied using visual census and mark-recapture methods. Size and abundance of piscivores (including large adult grunts) known to prey on grunts were greater within the reserve than on adjacent reefs, whereas size and abundance of older juvenile grunts did not differ between protected and exploited reefs. Recruitment and early juvenile abundance were lower within the reserve and were inversely related to predator density (including adult conspecifics). Patterns in density of new recruits may also have been influenced by oceanographic patterns of supply of larvae. Thus, although protection has a significant positive effect on the size and abundance of large carnivorous fishes, higher predation pressure within a reserve may serve to reduce juvenile recruitment within the reserve. At some size/age, cumulative recruitment due to lower size-specific predation mortality results in higher density within the reserve. This increased density is maintained by the absence of fishing mortality within the reserve. Despite maintaining high spawning biomass of several large, commercially exploited species that may export larvae to downstream areas, the Barbados Marine Reserve appears to be a local sink for juvenile grunts.