Reef Fisheries Research Articles

Climate change and the future for coral reef fishes

AbstractClimate change will impact coral‐reef fishes through effects on individual performance, trophic linkages, recruitment dynamics, population connectivity and other ecosystem processes. The most immediate impacts will be a loss of diversity and changes to fish community composition as a result of coral bleaching. Coral‐dependent fishes suffer the most rapid population declines as coral is lost; however, many other species will exhibit long‐term declines due to loss of settlement habitat and erosion of habitat structural complexity. Increased ocean temperature will affect the physiological performance and behaviour of coral reef fishes, especially during their early life history. Small temperature increases might favour larval development, but this could be counteracted by negative effects on adult reproduction. Already variable recruitment will become even more unpredictable. This will make optimal harvest strategies for coral reef fisheries more difficult to determine and populations more susceptible to overfishing. A substantial number of species could exhibit range shifts, with implications for extinction risk of small‐range species near the margins of reef development. There are critical gaps in our knowledge of how climate change will affect tropical marine fishes. Predictions are often based on temperate examples, which may be inappropriate for tropical species. Improved projections of how ocean currents and primary productivity will change are needed to better predict how reef fish population dynamics and connectivity patterns will change. Finally, the potential for adaptation to climate change needs more attention. Many coral reef fishes have geographical ranges spanning a wide temperature gradient and some have short generation times. These characteristics are conducive to acclimation or local adaptation to climate change and provide hope that the more resilient species will persist if immediate action is taken to stabilize Earth’s climate.

Shifting dominance among Scarid species on reefs representing a gradient of fishing pressure

The present paper analyzes data collected between 2001 and 2002 on 81 reef fish species targeted by fishers at 5 sites in the Kingdom of Tonga (South Pacific). We first ranked the sites with respect to fishing pressure using two independent methods: (i) Tongan demography and reef surfaces available for fishing, and (ii) the differential effects of fishing on the whole set of 81 species grouped by their life history traits (LHT). We then focused on Parrotfish (Scaridae), which are heavily targeted in coral reef fisheries. We used the identified gradient of fishing pressure to study the effect of fishing on the community structure and test the hypothesis of “shifting dominance” amongst the 20 Scarid species present in the surveys. In addition to the classical effect of decreasing fish size in a family strongly targeted by fishers, the shifting dominance phenomenon includes a decrease in the abundance of the large-bodied and highly targeted species, favouring their replacement by smaller-bodied species from the same family, which are less impacted by fishing. In a context of interspecific competition amongst Scarids, the stress of fishing appears as a factor favouring the replacement of species with large maximum size, and LHT promoting low resilience, by smaller species with the opposite attributes. The discussion focuses on the various processes that can explain the shifting dominance phenomenon. The total density of resilient species, which increased along the gradient of increasing fishing pressure, can be used as an indicator of the over-exploitation of fish communities for reef fisheries management.

A framework for adaptive gear and ecosystem‐based management in the artisanal coral reef fishery of Papua New Guinea

1. Artisanal fishing on coral reefs in Papua New Guinea is an important livelihood activity that is managed primarily at the level of local communities. Pockets of overexploitation exist and are expected to increase with plans for increased commercialization. 2. This paper provides a current assessment of the artisanal multi-species coral reef fishery by examining selectivity of the dominant gear, namely line fishing, spearguns, and gill nets. Each gear has its own strengths and weaknesses in terms of use and conservation of resources, with no clear problem gear. 3. The three gears utilize different resources but there was moderate overlap in the species caught, particularly between gill nets and line fishing and marginally between lines and spearguns. Gill nets have the disadvantage of being destructive to coral and the advantage of catching commercial species. Line fishing catches an intermediate number of species but mostly large-bodied and predatory species that could potentially reduce predation and the mean trophic level of the fishery. Spearguns catch the highest numbers of species, including many non-commercial and herbivorous fish and could reduce the diversity of fish and encourage algal growth. 4. This information could be used in combination with scientific monitoring and traditional ecological knowledge to develop an adaptive management framework that uses local restrictions on the various gears to restore or balance the fishery and ecosystem. Restrictions could be selectively imposed: on gill nets when coral cover is low, line fishing when large-bodied predators are depleted, and spearguns when biodiversity is reduced and algal abundance high. Copyright © 2008 John Wiley & Sons, Ltd.

Exploring optimal fishing scenarios for the multispecies artisanal fisheries of Eritrea using a trophic model

This study represents the first attempt to assess the potential for fisheries in the artisanal Red Sea reef fisheries of Eritrea in an ecosystem context. We used an Ecopath with Ecosim model to integrate known aspects of the ecosystem and its inhabitants into a single framework, with the aim to gain a better insight into the structure and functioning of the ecosystem and to assess the impacts of fishing in these data-limited fisheries. Model outputs indicate that most of the primary productivity in the system is recycled through a detritus-based food web, implying a bottom-up energy flow control. Ecotrophic efficiencies were nevertheless higher at higher trophic levels, suggesting that top-down control mechanisms are also ecologically important. Notwithstanding a high degree of primary productivity, the fishery yields estimated for the coral reef ecosystem were relatively low, apparently because of lower ecotrophic efficiencies at the lower trophic levels. A retrospective simulation of trends in these fisheries using Ecosim showed that, given the existing fishing intensity as suggested by official statistics (0.114 tonnes km −2 year −1), fishery-induced decline in abundance and yield of reef-associated demersals of the magnitude (ca. 25%) suggested by a previous study are unlikely. However, the decline in yield observed in these fisheries could be reproduced in the simulation when the existing fishing level was assumed to be five-fold the official estimate, as suggested by anecdotal evidence on unreported catches. The simulation results show that an optimal fishing strategy could be achieved through a slight reduction in the annual catch of reef-associated fish (to 0.32 tonnes km −2 year −1) and an increase in the capture of near-reef pelagics and large pelagics (to 0.19 and 0.39 tonnes km −2 year −1, respectively) from the putative levels. We explored optimal fishing scenarios in view of both direct effects of fishing on target species and indirect effects of fishing on non-target organisms. Finally, this study demonstrates that, even if modeling is no substitute for rigorous assessment of individual fish stocks with more detailed data, it could improve our understanding of the impacts of fishing on the structure and functioning of coral reef ecosystems in such newly developing fisheries, particularly on groups that would otherwise be difficult to monitor.

Characterization and management of the commercial sector of the Pohnpei coral reef fishery, Micronesia

Commercial coral reef fisheries in Pohnpei (Micronesia) extract approximately 1,521 kg of reef fish daily (*500 MT year -1 ) from 152 km 2 of surrounding reef. More than 153 species were represented during sur- veys, with 25 species very common or common within combined-gear catch. Acanthurids contributed the greatest to catch volume, with bluespine unicornfish, Naso uni- cornis, and orangespine unicornfish, Naso lituratus, among the most frequently observed herbivores. Nighttime spearfishing was the dominant fishing method and inner lagoon areas were primarily targeted. A seasonal sales ban (March-April), intended to reduce pressure on reproduc- tively active serranids, significantly increased the capture volume of other families. Catch was significantly greater during periods of low lunar illumination, suggesting higher fishing success or greater effort, or both. The marketed catch was dominated by juveniles and small adults, based on fishes of known size at sexual maturity. Artificially depressed market prices appear to be catalyzing (potential or realized) overfishing by increasing the volume of fish needed to offset rising fuel prices. These results support the need for comprehensive fisheries management that pro- duces sustainable fishing and marketing practices and promotes shared management and enforced responsibilities between communities and the state. To be effective, management should prohibit nighttime spearfishing.

Shifting baselines in fishers' perceptions of island reef fishery degradation

We present the first quantified evidence of shifting environmental baselines from an island coral reef fishery (Rodrigues). As depletion of commercial fish species spreads out from the coast youngsters share few of their elders' memories of former abundance. Of three generations, the oldest reported more fish species as depleted ( p ≤ 0.001), including predators indicative of ecosystem health and of interest to tourists. They recalled larger catches of the most-cited species Epinephelus multinotatus and bigger fish ( p < 0.001). Generations also differed in their perceptions of island-level environmental change. Shifting baseline studies may be useful when planning Marine Protected Areas (MPAs) in data-poor countries prioritising sustainable development.

A quantitative comparison of recreational spearfishing and linefishing on the Great Barrier Reef: implications for management of multi-sector coral reef fisheries

This study compared the catch composition, catch per unit effort, and incidental impacts of spearfishers and linefishers engaged in a structured fishing program whereby fishing effort was standardized across time, space and skill level. It was found that (1) the catch composition of both groups of fishers overlapped considerably, (2) the numbers of target fish caught by spearfishers (156) and linefishers (168) were not significantly different, (3) the mean size of target fish caught by spearfishers (1.95 ± 0.1 kg, ±SE) was significantly larger than the mean size of target fish caught by linefishers (1.27 ± 0.06 kg), and (4) spearfishers retained 43% more biomass of target species than did linefishers (304 versus 213 kg, respectively). However, linefishers used ∼1 kg of bait for every 3 kg of target fish that were captured. Linefishers also caught far more undersized, undesirable, or protected fishes (i.e., bycatch) and caused far more pollution (i.e., lost gear) than did spearfishers. It is concluded that the overall impacts of recreational spearfishing and linefishing on fishery resources of the Great Barrier Reef are broadly equivalent (per unit of fishing effort), and that management regulations should be applied equitably across both fishing sectors. A management strategy of this type will simplify enforcement of fisheries regulations and avoid discrimination of particular fishers in local communities where both fishing methods are socially or culturally important.

Rapid shifts in catch composition in the artisanal Red Sea reef fisheries of Eritrea

Shifts in catch composition were registered in the Eritrean artisanal fisheries, which were launched into a renewed development after the end of the independence war in 1991. Our analysis of catch and effort data showed that total fishing effort as well as total annual catch increased more than two-fold from 1996 to 2002. Yet, overall CPUE remained unchanged upon the expansion of the fisheries, suggesting that the fisheries are still at an early stage of development. However, at lower taxonomic level, we found that the CPUE for emperors (Lethrinidae), snappers (Lutjanidae), and sharks (Elasmobranchii) decreased, while the CPUE for barracudas (Sphyraenidae), jacks (Carangidae), and tunas (Scombridae) increased. Thus, the species composition of the catches shifted toward a smaller proportion of high-value demersals (from ca. 70% in 1996 to ca. 30% in 2002), implying a change in the underlying fish community structure. Changes in CPUE could not be attributed to changes in spatial effort allocation, or to changes in gear or boats used, ruling out changes in fishing strategies as likely causes. Yet the decline in CPUE at low fishing effort does not necessarily reflect a proportional decline in fish abundance, and could possibly be caused by “hyperdepletion”. Nevertheless, the trends in CPUE are consistent with earlier findings that stocks of reef-associated demersal fishes are highly vulnerable to fishing and can decline even at the early stages of the fisheries. Therefore, the changes in CPUE could indeed represent true biomass changes, with potentially important ecological consequences. These effects could even become more severe if market conditions improve, leading to activation of latent fishing capacity, which was found to make up about 75% of the registered fleet.

Current and Future Sustainability of Island Coral Reef Fisheries

Overexploitation is one of the principal threats to coral reef diversity, structure, function, and resilience [1, 2]. Although it is generally held that coral reef fisheries are unsustainable [3-5], little is known of the overall scale of exploitation or which reefs are overfished [6]. Here, on the basis of ecological footprints and a review of exploitation status [7, 8], we report widespread unsustainability of island coral reef fisheries. Over half (55%) of the 49 island countries considered are exploiting their coral reef fisheries in an unsustainable way. We estimate that total landings of coral reef fisheries are currently 64% higher than can be sustained. Consequently, the area of coral reef appropriated by fisheries exceeds the available effective area by approximately 75,000 km(2), or 3.7 times the area of Australia's Great Barrier Reef, and an extra 196,000 km(2) of coral reef may be required by 2050 to support the anticipated growth in human populations. The large overall imbalance between current and sustainable catches implies that management methods to reduce social and economic dependence on reef fisheries are essential to prevent the collapse of coral reef ecosystems while sustaining the well-being of burgeoning coastal populations.

Discard composition and release fate in the snapper and grouper commercial hook‐and‐line fishery in North Carolina, USA

Abstract Minimum size limits may be ineffective for reef fishes because they often sustain barotrauma when caught from deep (&gt;20 m) waters. A study was undertaken in conjunction with hook‐and‐line commercial fishermen to calculate discard percentages and evaluate potential release mortality of eight economically important species: black sea bass, Centropristis striata (Linnaeus), red grouper, Epinephelus morio (Valenciennes), snowy grouper, Epinephelus niveatus (Valenciennes), gag, Mycteroperca microlepis (Goode and Bean), scamp, Mycteroperca phenax (Jordan and Swain), vermilion snapper, Rhomboplites aurorubens (Cuvier), white grunt, Haemulon plumieri (Lacepède) and red porgy, Pagrus pagrus (Linnaeus). Fishing with baited hook and line occurred in 2004 and 2005 in Onslow Bay, NC, in waters 19–150 m deep. Sub‐legal discard rates were 15% for vermilion snapper, 25% for red porgy, 7% for red grouper, 33% for gag, 35% for scamp and 12% for black sea bass. Although mortality based on post‐release behaviour was relatively low, higher mortalities estimated from models incorporating hooking location and depth of capture suggest that minimum size limits may not provide the population benefits intended by management in the North Carolina reef fishery.

Malthusian overfishing in Pulau Banggi?

Abstract We assess, based on fisheries and interview data collected on-site, whether Malthusian overfishing is occurring in Pulau Banggi, Sabah. Fisheries resources in Pulau Banggi have been perceived to be declining over the past 20 years, and characteristics of Malthusian overfishing are evident, although not at a magnitude comparable with other more heavily exploited artisanal fisheries in the Philippines. It appears that Pulau Banggi's reef fisheries are at an early stage of Malthusian overfishing, and this is therefore a critical time for addressing and mitigating drivers of overfishing to prevent inevitable and further decline of Pulau Banggi's reef fisheries.

Seasonality and historic trends in the reef fisheries of Pulau Banggi, Sabah, Malaysia

The reef fisheries of Pulau (meaning “island” in Malay) Banggi, Sabah are not managed, and lack baseline fisheries data despite forming part of a proposed marine park. Thus, a combination of qualitative and quantitative approaches was applied to obtain a baseline picture about the past and present state of the fisheries. Fish landings were monitored, and fisher interviews conducted to investigate seasonal effects and historical changes in Banggi’s reef fisheries. Monsoon winds were a major driver of seasonal differences in catch quantities for the hook and line, but not the gillnet fishery. Spatial distribution of fishing effort and target species also differed by season. Fishers consistently indicated that Banggi’s fisheries were declining, with a suggested three to four times decrease in catch rates over the last 20 years. Interestingly, it appeared that substantial decreases began in the year 2000. The responses of fishers to seasonal changes, and the resultant implications for management are discussed. Importantly, the need for immediate management policies to prevent further declines and to maintain sustainable reef fisheries is stressed.

Effectiveness of five small Philippines’ coral reef reserves for fish populations depends on site-specific factors, particularly enforcement history

Community-managed, no-take marine reserves are increasingly promoted as a simple, precautionary measure to conserve biodiversity and sustain coral reef fisheries. However, we need to demonstrate the effects of such reserves to those affected by the loss of potential fishing grounds and the wider scientific community. We surveyed changes in fish communities in five small marine reserves in the central Philippines and three distant Control sites over seven years. We conducted underwater visual censuses of 53 fish families within the reserve (Inside), with a kilometre of the boundary (Outside) and at Control sites. We found significant differences between fish communities Inside and Outside the reserve only at the two sites with strictest compliance with fishing prohibition, while there were significant differences to distant Control sites in all cases. The strongest responses to reserve protection were found in predatory fishes (groupers and breams) and in butterflyfish. Other abundant fish families showed weak effects of protection. For all taxa analysed, we found significant effects of reserve Site and Site × Treatment interactions. The detection of fish responses to reserves is complicated by potential spillover effects, site-specific factors, particularly compliance, and the difficulty of identifying appropriate control areas.

In vitro hybridization of coral trouts, Plectropomus leopardus (Lacepède, 1802) and Plectropomus maculatus (Bloch, 1790): a preliminary investigation

[Extract] Coral trouts of the genus Plectropomus are members of the serranid subfamily Epinephelinae, which are commonly known as groupers. Two of these species, Plectropomus leopardus (Lacepede, 1802) and Plectropomus maculatus (Bloch, 1790), are among the most popular and valuable of the groupers, and both species are major targets of reef fisheries which operate throughout the Indo-West Pacific region (Williams 2002; Sadovy, Donaldson, Graham, McGilvray, Muldoon, Phillips, Rimmer, Smith & Yeeting 2003). Much of the catch is exported to Hong Kong, where the retail price of live specimens ranges from US$50 to 75 per kg (Sadovy et al. 2003). This high value has resulted in a strong demand for coral trouts and an upward trajectory in their total annual harvest (Williams 2002; Sadovy et al. 2003). Fishing pressure has significantly decreased the abundance of coral trouts in parts of Australia and Southeast Asia (Sadovy et al. 2003; Evans & Russ 2004); thus, there is a need to develop more sustainable methods of supplying coral trouts to the market. Although there have been many previous attempts to culture these fish in Australia and Southeast Asia, most have been unsuccessful, largely due to problems associated with the acceptance of live feeds by early larval stages (Rimmer, Garrett & Samoilys 1994; Sadovy et al. 2003).

Open access in a spatially delineated artisanal fishery: the case of Minahasa, Indonesia

The effects of economic development on the exploitation of renewable resources are investigated in settings where property rights are ill defined or not enforced. This paper explores potential conservation implications from labor and product market developments, such as enhanced transportation infrastructure. A model is developed that predicts individual fish catch per unit effort based on characteristics of individual fishermen and the development status of their villages. The econometric model is estimated using data from a cross-sectional household survey of artisanal coral reef fishermen in Minahasa, Indonesia, taking account of fishermen heterogeneity. Variation across different villages and across fishermen within the villages is used to explore the effects of development. Strong evidence is found for the countervailing forces of product and labor market effects on the exploitation of a coral reef fishery.

Reef fisheries management in Kenya: Preliminary approach using the driver–pressure–state–impacts–response (DPSIR) scheme of indicators

This paper reviews the present state of reef fishing activities in Kenya and the tropics using the driver–pressure–state–impacts–response (DPSIR) framework. It identifies appropriate indicators that would evaluate the problem of overfishing and the use of destructive fishing gear, and discusses policy considerations for the Kenyan small-scale fishery. We conclude that the DPSIR framework works well at simplifying the complexity of reef fisheries management and serves to inform policy makers, scientists and general public on the relevance of indicators to monitor changes in the status of reefs.

No-take Marine Reserves and Reef Fisheries Management in the Philippines: A New People Power Revolution

The marine-conservation and reef fisheries-management program that exists today in the Philippines had humble beginnings in the 1970s at Sumilon and Apo islands. These islands have produced some of the best evidence available that no-take reserves, protected and managed by local communities, can play a key role in biodiversity conservation and fisheries management. Perhaps more importantly, they served as models for an extraordinary expansion of no-take reserves nationally in the Philippines in the past 2 decades. This expansion contributed substantially to a major shift in national policy of management of marine resources. This policy shift partially devolved responsibility from a centralized government bureaucracy to local governments and local communities. Local governments now comanage, along with the national government, marine resources out to 15 km from the coast. Giving some responsibility for management of marine resources to coastal people dependent upon those resources represents, in a very real sense, another "people power revolution" in the Philippines.

Socioeconomic factors that lead to overfishing in small-scale coral reef fisheries of Papua New Guinea

The coral reefs of Papua New Guinea are among the most species diverse in the world, support an important artisanal fishery, but lack an effective national conservation programme. Increased commercialization, population growth, promotion of fisheries development projects, and the live reef food fish trade are expected to increase demand for the country's reef fish. This paper examines how socioeconomic factors affect the condition of the artisanal multi-species coral reef fishery in six sites in Papua New Guinea. Catch characteristics such as diversity, trophic level and body size by landing site were examined along a fishing pressure gradient. Both exogenous factors such as markets and endogenous factors such as fishing pressure were related to the condition of fish catch. In general, the trophic level and lengths of fish captured in Papua New Guinea were relatively high, but were reduced on reefs with high fishing effort near fish markets. Fisheries showed signs of depletion above c. 25 fishing trips per km2 per day and the proximity of markets was a better indicator of overfishing than human population size. A cross-scale approach to fisheries management is required in Papua New Guinea to coordinate decentralized local management, limit the intrusion of extractive enterprises, and develop policies that seek to minimize exogenous pressures on marine resources.

A univariate and multivariate study of reef fisheries off northeastern Brazil

Abstract This work was part of a programme to assess the potential living resources within the Exclusive Economic Zone (EEZ) of Brazil that collected information on the catch composition and biology of the main species within the zone (REVIZEE). It aimed to identify and, using statistical tools, to assess the factors that influence the dynamics of the demersal fishery, targeting the rocky, coral reef and associated sandy seabeds of the continental shelf. Within the reef fishery of northeastern Brazil, snappers (family Lutjanidae), in particular Lutjanus chrysurus, L. synagris, L. analis, L. jocu, and, to a lesser extent, L. vivanus, are the main artisanal catch and contribute most to the similarity between groups. Among the factors considered, the spatial effect (geopolitical state as a factor) appeared to be the strongest attribute in isolating groups. Of the technological factors, trip duration better discriminated the catch composition than fleet category. However, given some exceptions mainly linked to favourable strong wind, trip duration categories were usually related to fleet dynamics, because motorized boats generally undertake longer trips. Such characteristics are important for management decisions, because fleets are likely to exploit different stages of the life cycle of a fish as well as different species while operating in different geographical areas. The catch analysis was characterized by a “lutjanid community” typical of rock, coral, and coral-sand habitats, and it is clear that this community is dominant in Brazil as well as in the more usually quoted regions such as the Bahamas, Antilles and along the coast from Yucatan to Panama.

Effects of fishing and protection on Brazilian reef fishes

The vast Brazilian coast harbors unique and diverse reef fish communities. Unfortunately, relatively little is known about the impact of fishing on these fish species, and few management or conservation efforts are being made to protect them. Here, we examine the effect of different levels of protection on the composition, abundance, and size structure of reef fish species along a 2500 km portion of the Brazilian coastline, noting in particular the relative abundance of endemics and the effect of protection on these species. Pairwise comparisons of sites with different protection status (more versus less protected) were used to determine the potential responses of reef fishes to the establishment of marine protected areas. Highly targeted species (top predators and large herbivores) were significantly more abundant and larger in size within sites with a higher degree of protection, indicating that they benefit from protection, while lightly fished and unfished species were not. These results are consistent with past work documenting the responses of species to protection. Here, we use our results in particular to suggest strategies and provide expectations for managing and protecting Brazilian reef fisheries. Because this biogeographic province lies entirely within the jurisdiction of a single nation, there may be unique and significant opportunities to effectively manage and conserve these fish species.