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Coral reefs have served as a source of many useful products for humankind for ages. The most important product is fish. Exploitation of reef resources during the early twentieth century did not have much discernible negative effects on coral reef ecosystems in some parts of Southeast Asia (e.g. some areas in central Philippines), probably because of the small numbers of people exploiting the resources. This situation has changed dramatically. Human-induced stresses exacerbated by occasional natural perturbations such as coral bleaching and infestations of crown-of-thorns starfish threaten the survival of coral reef ecosystems. It is estimated that 30% of coral reefs has already been severely damaged and close to 60% may be lost by 2030 (Wilkinson, 2004). The 20 000 km2 of Philippine coral reefs are no exception. Destructive fishing and sedimentation have taken a heavy toll of this fragile ecosystem. Only about 30% of coral reef stations surveyed remain in good to excellent condition (Gomez et aI., I994).

As well as serving valuable biodiversity conservation roles, functioning no-take fishery reserves protect a portion of the fishery stock as insurance against future over-fishing. So long as there is adequate compliance by the fishing community, it is likely that they will also sustain and even enhance fishery yields in the surrounding area. However, there are significant gaps in scientific knowledge that must be filled if no-take reserves are to be used effectively as fishery management tools. Unfortunately, these gaps are being glossed over by some uncritical advocacy. Here, we review the science, identify the most crucial gaps, and suggest ways to fill them, so that a promising management tool can help meet the growing challenges faced by coastal marine fisheries.

Coral reefs have traditionally supplied coastal human populations with fishery products. Reef fisheries constitute about 20% of the total marine production (1.64 million mt) in the Philippines, as of the late 1990s. Based on the total area of coral reefs, which is 25,000 km2, and the average fish yield of good reefs, estimated at 15 mt·km2·yr, the potential annual production of Philippine coral reefs would be about 350,000 mt. Since only 30% remains in good condition and 70% is in degraded condition, this estimated annual production have been reduced to about 177,500 mt as of the 1990s. Coral reef fisheries in the central Philippines comprise about 125 reef and reef-associated species distributed in 14 families. Aside from being over-fished, the Philippine coral reefs have been damaged by the use of destructive fishing methods. The high intensity of fishing (up to 50% of fish standing stock removed by fishing annually) has resulted in the depletion of fishery species. Protection of reefs occurs at a slow rate, indicating a need to increase efforts at establishing marine reserves and restoring degraded reefs to stabilize or enhance fish yields.

[Extract] The term "marine reserves" is defined in this chapter to simply mean "no-fishing" areas in the marine environment, that is, areas permanently closed to fishing. The goal in this chapter is to review some of the major issues of marine reserves as reef fisheries management tools. Other benefits of marine reserves, including maintenance of biodiversity and ecosystem structure and enhanced tourism, have been reviewed many times elsewhere (Table 1). Marine reserves are not being advocated here as the only, or even the optimum, method of reef fisheries management. In fact, it is vital to stress from the outset that other forms of fisheries and habitat management should be encouraged and attempted in areas open to fishing. In addition, in many developing nations, managing fisheries on coral reefs requires that the number of fishers be reduced considerably (Munro and Williams, 1985; Russ, 1991; Munro, 1996). Without such measures as finding alternative livelihoods for fishers and reducing rates of human population growth, most attempts at managing reef fisheries will probably be futile in many developing nations. In the past decade the topic of marine reserves as potential fisheries management tools has produced a burgeoning literature (Tables 1 and 2). There are at least two major reasons for this. First, scientists working in developing nations and/or on the management of coral reef fisheries (e.g., A. C. Alcala, J. A. Bohnsack, G. E. Davis, T. R. McClanahan, N. V. C. Polunin, and C. M. Roberts) have realized that there are probably few other viable management alternatives. In such situations it is almost socially immoral to try to impose fishing effort or catch restrictions on subsistence and artisanal fishers. You cannot tell a fisher in a developing nation ttlat they must throw a fish back into the ocean because it is too small, or that they must catch only four fish per day when they have eight family members to feed. Second, traditional fisheries management (effort, catch controls) has generally failed to prevent massive overfishing globally. The dismal state of most of 20 stocks of cod in the North Atlantic, exploited by the highly developed nations of Canada, the United States, and Europe, are good examples of this (Myers et al., 1996). Marine reserves are now seen as an insurance policy against such management failures, something Jim Bohnsack was advocating for reef fisheries a decade ago [Plan Development Team (PDT), 1990].

SummaryNo-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).

Age and growth parameters of Orectolobus hutchinsi were estimated using micro-radiographs of sectioned vertebrae from 182 wild caught individuals. Two fluorochrome marker dyes, calcein and oxytetracycline, were used to validate the timing and periodicity of vertebral band formation in nine individuals held in the laboratory for between 423 and 472 days. Growth bands were difficult to interpret and final counts were obtained from only 98 (53.8%) individuals ranging in total length (TL) from 63 to 146 cm. The timing of growth band formation in the vertebrae of captive animals had no predictable temporal pattern, with formation occurring during all seasons of the year, making age validation difficult. Growth band formation was hypothesised to be influenced by non-periodic changes in centrum or somatic growth rather than seasonal growth, as observed in many other elasmobranch species. Growth rates of nine O. hutchinsi held in captivity varied considerably, ranging from 3.5 cm year–1 to 13.8 cm year–1 in total length (mean = 7.03 cm year–1). Although the periodicity of vertebral band formation in captive animals did not support a synchronous annual pattern, captive growth rates matched those predicted when an annual band pattern was assumed for wild caught individuals. Von Bertalanffy growth parameters estimated from vertebral analysis assuming an annual banding pattern and a mean size of birth of 24.1 cm were: L∞ = 149.45 cm and K = 0.117 year–1 for both sexes combined. These results illustrate the fundamental importance of validating the periodicity of growth band formation in elasmobranch age and growth studies as it has considerable implications for the management of fisheries that exploit shark and ray species that may exhibit asynchronous growth band deposition.

Fish yields and catch rates recorded in the 1980s were compared with daily roving creel surveys carried out in 1997/98, 2000 and 2001 at Apo Island. Total annual fish yields were measured six times over the period 1980–2001. Total fish yield was 19–25 t km–2 year–1, with reef and reef-associated fish accounting for 15–20 t km–2 year–1, for five measurements. A sixth measurement, made in 1986, estimated 36.7 t km–2 year–1. Annual yield remained stable over the study period. Carangidae and Acanthuridae accounted for 26–47% and 16–27% of the catch, respectively. Non-reef catches declined over time, from 6.21 t year–1 in 1980/81 to 1–2 t year–1 in 2000 and 2001. Estimates of annual hook and line catch per unit effort (CPUE) increased from 0.13–0.17 kg man–1 h–1 in 1980/81, to 1–2 kg man–1 h–1 in 1997–2001. For target families, hook and line CPUE was consistently higher in 1997–2001 than in 1980–86. However, hook and line CPUE for Carangidae and Acanthuridae declined significantly between 1997 and 2001. Possible reasons for the long-term patterns of fish yields and catch rates are discussed. Differences in methods used in estimates, and changes in gears and fishing effort over the years, make comparisons difficult.

A mark–release–resighting (MRR) technique was used to estimate population size of the coral trout, Plectropomus leopardus, on coral reefs fringing Lizard Island, Great Barrier Reef, Australia. Fish were captured by hook-and-line fishing, and marked with individual freeze-brand numbers in August 1995. An underwater visual census (UVC) technique was used during September and October 1995 both for resighting of marked fish and to make an independent estimate of fish density and thus population size. The study area was 750 966 m2 . The UVC sampled 154 000 m2 (20.5%) of this area. Six different methods of analysis of MRR gave similar population size estimates (e.g. Petersen 12 873; 95% CI 9989–15 754) extrapolated to the 4.5 million-m2 reef area from datum to 20-m depth around Lizard Island. UVC gave a population size estimate (24 182; 95% CI 21 860–26 504) twice that of MRR. The lower estimate derived from MRR may be the result of tag-induced mortality, or of the relative difficulty in discriminating between marked and unmarked trout by UVC. This is only the second estimate of population size of coral trout on an area of the Great Barrier Reef.

From 1990 to 1993, samples of coral trout, Plectropomus leopardus, were collected at two coral reefs closed to fishing since 1987 in the central Great Barrier Reef (GBR). The age structure was dominated by a strong cohort which settled in early 1984 and which accounted for 54%, 45%, 42% and 36% of the experimental hook-and-line catches at Glow and Yankee reefs. Catch rates (fish person-1 hour-1) per age class per reef per year provide the first reliable estimates of the exponential rate of mortality of coral trout in zones of the GBR Marine Park closed to fishing. The annual mortality rate between the ages of 6 and 9 years was 0.115 (s.e. 0.040) at Glow reef and 0.189 (s.e. 0.100) at Yankee reef. The annual mortality rate between ages 6 and 9 years was 0.147 (s.e. 0.028) at the two reefs combined. Age-specific estimates of annual mortality ranged from 0.024 (age 7–8 at Glow) to 0.442 (age 6–7 at Yankee) but were unreliable because of small sample sizes. This is one of the first estimates of mortality rate of an exploited species in an area closed to fishing in the tropics.

Visual censuses were used to quantify the distribution and abundance of the Lutjanidae, Lethrinidae and Serranidae in three reef zones (windward reef slope, lagoon, back reef) of three reefs on the mid shelf and three reefs on the outer continental shelf in the central region of the Great Barrier Reef. Significant spatial variability was identified in the abundances of many species between locations (outer-shelf and mid-shelf communities), between reefs (high-abundance v. low-abundance reefs), and within reefs (characteristic communities within zones on individual reefs). Species of the Lutjanidae, Lethrinidae and Serranidae were found to occur in assemblages that were characteristic of major zones (windward reef slopes, lagoons and leeward back reefs), this pattern being consistent within and among shelf locations. Care will need to be taken in determining the appropriate spatial scales of sampling in any future experiments (e.g. manipulations of fishing pressure) to ensure that the effects of smaller-scale spatial differences are not confounded when larger-scale comparisons are made.

The age and growth of Lutjanus adetii and L. quinquelineatus from the central Great Barrier Reef were determined from studies of annuli in sectioned otoliths (sagittae). The period of annulus formation was validated by oxytetracycline labelling of externally tagged fishes. For L. adetii, validation was obtained from tagged fishes that were recaptured after a minimum of 12 months at liberty, the first time this has been achieved for a Lutjanus species. A single opaque and translucent zone was formed once a year, with the opaque band (annulus) being formed during the winter months. Otolith weight was strongly correlated with age for both species. There was significant differential growth between the sexes in length-at-age and weight-at-age for both species, with males growing larger than females. The oldest individuals found were a male L. adetii of 24 years of age and a female L. quinquelineatus of 31 years of age. The shape of the growth curves were steep for the first few years and then became asymptotic. The annual instantaneous rate of natural mortality (M) was 0.235 for L. adetii and 0.154 for L. quinquelineatus, representing an annual survivorship of 79% and 86%, respectively. The protracted longevity and low natural mortality rates imply that both L. adetii and L. quinquelineatus are vulnerable to overfishing despite their small size.

Age and growth of the inshore coral trout P. maculatus from the central Great Barrier Reef region was determined by studies of annuli in whole and sectioned sagittae. The periodicity of formation of the annulus was validated through tetracycline labelling of mark-recaptured fishes in the wild and of captive fishes in aquaria. Results obtained from three recaptured and five captive fishes showed that annuli are formed once a year during late winter and spring months. von Bertalanffy growth-curve parameters were L∞ = 60.00 cm SL, K= 0.206 and to = - 0.945 year. The oldest specimen examined was a 12-year-old male of 58 cm SL. The total rate of mortality (Z) was estimated to be 0.569.

The effects of predation by fishes, competition, and structural complexity of the substratum on the species composition and diversity of an epifaunal community in the marine subtidal region have been studied. Artificial substrata (panels) were used to monitor the establishment of the community and cages were used to exclude grazing fishes (mainly juvenile Penicipelta vittiger (Castelnau) (Monacanthidae)). Caged surfaces immersed for 7 mth were dominated by two species of colonial ascidian. On control surfaces, selective removal of newly settled ascidians by fishes prevented severe competition between the ascidians and other invertebrates, particularly arborescent and encrusting bryozoans. Fish grazing thus prevented monopolization of space by a dominant competitor, and resulted in a significantly higher community diversity and a significantly lower standing crop. On surfaces carrying models of arborescent bryozoan communities the foraging efficiency of fishes was reduced and the survival of colonial ascidians was enhanced. The settlement of a species of sponge was also enhanced on these complex substrata.

This paper describes an experiment designed to measure the standing crop and the per unit area rates of production of algal tissue and yield to large grazers of the epilithic algal community (EAC) inside and outside the territories of the herbivorous pomacentrid Stegastes fasciolatus (Ogilby) on an outercontinental shelf coral reef in the central Great Barrier Reef. Standing crop of the EAC was significantly higher inside(29.25 g C · m −2 ,95% C . L . = 2.59) than outside (18.45 g C · m −2 ,95% C . L . = 3.02) territories. Rates of production of algal tissue inside and outside territories were respectively 1.20 (95% C . L . = 0.23) and 0.69 (95 % C.L. = 0.22) g C · m −2 · day −1 . Rates of yield to large grazers inside and outside territories were respectively 0.98 (95% C . L . = 0.33) and 0.48 (95% C . L . = 0.39) gC · m −2 · day −1 .Neither production of algal tissue nor yield were significantly higher inside than outside territories because of high within-site variances. Rate of production of algal tissue did not differ significantly from yield both inside and outside territories. Grazing intensity measured as bite rates may be lower inside than outside territories but grazing intensity measured as rate of removal of algal tissue may be as high, if not higher, inside than outside territories.

This study describes the patterns of species richness and abundance of herbivorous grazing fishes (Acanthuridae, Scandae, Siganidae) in 5 zones (reef slope, reef crest, reef flat, lagoon, back reef) of 3 reefs on the mid-continental shelf and of 3 reefs on the outer continental shelf in the central region of the Great Barrier Reef. Herbivorous fishes (all 3 families considered together) occur in assemblages which are characteristic of several major zones and this pattern of zonation is consistent on the 6 reefs. Assemblages in deep, outer-slope zones are distinctive from those in shallow zones, There are distinctive assemblages of herbivorous fishes on reef flats, reef crests and over sandy areas in both lagoon and back reef zones. Similarity in these patterns of zonation between reefs suggests that they will be maintained through time. Families display distinctive patterns of zonation also, but patterns differ between families. Acanthurids and scarids generally have higher numbers of species and individuals on reef crests and in lagoons than on reef flats or reef slopes; siganids have higher numbers of species and individuals in lagoons and back reefs than in the other 3 zones studied, Variation in species richness and abundance of individual families between zones was, however, not consistent among reefs at the same shelf location. Different guilds of herbivorous fishes were distributed differently between zones. Suckers feeding on fine sediments were most abundant near windward and leeward edges of reefs; suckers feeding over sand were most abundant in back reefs and lagoons; large and small croppers and scrapers were more abundant in shallow zones (reef crest, reef flat, lagoon) than in deep zones (reef slope, back reef).

SummaryNetworks of no-take marine reserves (NTMRs) are widely advocated for preserving exploited fish stocks and for conserving biodiversity. We used underwater visual surveys of coral reef fish and benthic communities to quantify the short- to medium-term (5 to 30 years) ecological effects of the establishment of NTMRs within the Great Barrier Reef Marine Park (GBRMP). The density, mean length, and biomass of principal fishery species, coral trout (Plectropomus spp., Variola spp.), were consistently greater in NTMRs than on fished reefs over both the short and medium term. However, there were no clear or consistent differences in the structure of fish or benthic assemblages, non-target fish density, fish species richness, or coral cover between NTMR and fished reefs. There was no indication that the displacement and concentration of fishing effort reduced coral trout populations on fished reefs. A severe tropical cyclone impacted many survey reefs during the study, causing similar declines in coral cover and fish density on both NTMR and fished reefs. However, coral trout biomass declined only on fished reefs after the cyclone. The GBRMP is performing as expected in terms of the protection of fished stocks and biodiversity for a developed country in which fishing is not excessive and targets a narrow range of species. NTMRs cannot protect coral reefs directly from acute regional-scale disturbance but, after a strong tropical cyclone, impacted NTMR reefs supported higher biomass of key fishery-targeted species and so should provide valuable sources of larvae to enhance population recovery and long-term persistence.