Well-designed and effectively managed networks of marine reserves can be effective tools for both fisheries management and biodiversity conservation. Connectivity, the demographic linking of local populations through the dispersal of individuals as larvae, juveniles or adults, is a key ecological factor to consider in marine reserve design, since it has important implications for the persistence of metapopulations and their recovery from disturbance. For marine reserves to protect biodiversity and enhance populations of species in fished areas, they must be able to sustain focal species (particularly fishery species) within their boundaries, and be spaced such that they can function as mutually replenishing networks whilst providing recruitment subsidies to fished areas. Thus the configuration (size, spacing and location) of individual reserves within a network should be informed by larval dispersal and movement patterns of the species for which protection is required. In the past, empirical data regarding larval dispersal and movement patterns of adults and juveniles of many tropical marine species have been unavailable or inaccessible to practitioners responsible for marine reserve design. Recent empirical studies using new technologies have also provided fresh insights into movement patterns of many species and redefined our understanding of connectivity among populations through larval dispersal. Our review of movement patterns of 34 families (210 species) of coral reef fishes demonstrates that movement patterns (home ranges, ontogenetic shifts and spawning migrations) vary among and within species, and are influenced by a range of factors (e.g. size, sex, behaviour, density, habitat characteristics, season, tide and time of day). Some species move <0.1-0.5 km (e.g. damselfishes, butterflyfishes and angelfishes), <0.5-3 km (e.g. most parrotfishes, goatfishes and surgeonfishes) or 3-10 km (e.g. large parrotfishes and wrasses), while others move tens to hundreds (e.g. some groupers, emperors, snappers and jacks) or thousands of kilometres (e.g. some sharks and tuna). Larval dispersal distances tend to be <5-15 km, and self-recruitment is common. Synthesising this information allows us, for the first time, to provide species, specific advice on the size, spacing and location of marine reserves in tropical marine ecosystems to maximise benefits for conservation and fisheries management for a range of taxa. We recommend that: (i) marine reserves should be more than twice the size of the home range of focal species (in all directions), thus marine reserves of various sizes will be required depending on which species require protection, how far they move, and if other effective protection is in place outside reserves; (ii) reserve spacing should be <15 km, with smaller reserves spaced more closely; and (iii) marine A. L. Green and others reserves should include habitats that are critical to the life history of focal species (e.g. home ranges, nursery grounds, migration corridors and spawning aggregations),...
The utility of no‐take marine reserves as fisheries‐management tools is controversial. It is hypothesized that marine reserves will help to sustain fisheries external to them by becoming net exporters of adults (the “spillover effect”) and net exporters of propagules (the “recruitment effect”). Local fishery benefits from spillover will likely generate support from fishing communities for marine reserves. We used underwater visual census to show that biomass of Acanthuridae (surgeonfish) and Carangidae (jacks), two families of reef fish that account for 40–75% of the fishery yield from Apo Island, Philippines, tripled in a well‐protected no‐take reserve over 18 years (1983–2001). Biomass of these families did not change significantly over the same period at a site open to fishing. The reserve protected 10% of the total reef fishing area at the island. Outside the reserve, biomass of these families increased significantly closer to (200–250 m) than farther away from (250–500 m) the reserve boundary over time. We used published estimates of fishery catch and effort, and fisher interviews (creel surveys) to show that the total catch of Carangidae and Acanthuridae combined at Apo Island was significantly higher after (1985–2001) than before (1981) reserve establishment. Hook‐and‐line catch per unit effort (CPUE) at the island was 50% higher during 1998–2001 (reserve protected 16–19 years) than during 1981–1986 (pre‐reserve and early phases of reserve protection). Total hook‐and‐line effort declined by 46% between 1986 and 1998–2001. Hook‐and‐line CPUE of Acanthuridae was significantly higher close to (within 200 m) than far from the reserve. CPUE of Carangidae was significantly higher away from the reserve, possibly reflecting a local oceanographic effect. The benefits of the reserve to local fisheries at the island were higher catch, increased catch rate, and a reduction in fishing effort. The fishery and tourism benefits generated by the reserve have enhanced the living standard of the fishing community.
Size‐specific mortality can determine whether coral transplants become successfully established in a reef rehabilitation effort. Presented here are results of a study of size‐specific mortality in laboratory‐cultured transplants, and the mediating effect of fusion on their survival and growth. Culturing seeded colonies for transplantation minimizes impacts to source reefs. This strategy provides an opportunity to enhance survival of a transplanted population by incorporating selected aspects of colonial modular biology, such as fusion, into the culture phase. Despite efforts to develop a completely field‐based method, settlement and early survival of juveniles of the scleractinian Pocillopora damicornis were much higher in laboratory aquaria than among those settled on reef substrate, highlighting the difficulty of direct seeding and justifying the higher effort involved in laboratory rearing. Juvenile colonies from four size cohorts (≤3 mm, 3.1–6 mm, 6.1–10 mm, and 10.1–29 mm), outplanted to a reef in August 1997, showed one‐year survival of 0%, 2.5%, 16.3%, and 47.5%, respectively, illustrating significant size‐specific mortality. Colony fusion resulted in lower 6‐mo mortality (unfused colonies: 34.5% ± 0.4%, fused pairs: 14.0% ± 2.5%, fused groups: 8.3% ± 4.8%; means ± 1 se), and chimeras of >2 fused colonies produced polyps faster. Tissue necrosis along fusing colony borders was observed between 8‐mo‐old colonies. This suggested a rejection response, though colonies fusing prior to this age remained stable for up to one year. A transition matrix revealed that fused colonies showed greater probability of growth to the next size class, while unfused colonies showed higher mortality and stasis. Growth trajectories based on transition probabilities suggested that fused colonies would reach reproductive size much earlier than unfused colonies. To test the hypothesis that larvae aggregatively settle to increase their chances of fusing, settlement patterns were determined in larvae of same‐ vs. mixed‐parent groups. Settled larvae were aggregatively distributed, with no difference in aggregation strength in larvae of same‐ vs. mixed‐parent groups. Results suggest a benefit of fusion to survival and growth within the first eight months in juvenile coral colonies. Fusion could be used as a strategy to obtain larger colonies faster, provided they remain stable over time. Laboratory seeding and rearing of juveniles to 10 mm provides a workable alternative to fragment transplantation in brooding coral species, and similar strategies may also be developed for spawning species.
Coral reefs, the most diverse of marine ecosystems, currently experience unprecedented levels of degradation. Diseases are now recognized as a major cause of mortality in reef-forming corals and are complicit in phase shifts of reef ecosystems to algal-dominated states worldwide. Even so, factors contributing to disease occurrence, spread, and impact remain poorly understood. Ecosystem resilience has been linked to the conservation of functional diversity, whereas overfishing reduces functional diversity through cascading, top-down effects. Hence, we tested the hypothesis that reefs with trophically diverse reef fish communities have less coral disease than overfished reefs. We surveyed reefs across the central Philippines, including well-managed marine protected areas (MPAs), and found that disease prevalence was significantly negatively correlated with fish taxonomic diversity. Further, MPAs had significantly higher fish diversity and less disease than unprotected areas. We subsequently investigated potential links between coral disease and the trophic components of fish diversity, finding that only the density of coral-feeding chaetodontid butterflyfishes, seldom targeted by fishers, was positively associated with disease prevalence. These previously uncharacterized results are supported by a second large-scale dataset from the Great Barrier Reef. We hypothesize that members of the charismatic reef-fish family Chaetodontidae are major vectors of coral disease by virtue of their trophic specialization on hard corals and their ecological release in overfished areas, particularly outside MPAs.
Do no-take marine reserves affect fishery yields? Manipulations of reserve status, and yield estimates, were made at two Philippine islands over two decades. Twenty-five percent and ten percent, respectively, of the coral reefs at Sumilon and Apo islands were made no-take reserves in 1974 and 1982. Biomass of target fish increased inside the no-take reserves 3- to 4.5-fold over 918 years. Biomass did not increase outside each reserve. Protection of the Sumilon reserve ceased in 1984. Biomass of targeted fish in the reserve and trap and gillnet catches of these fish declined by 42.7% and 40%, respectively, by 1985. The reserve was reprotected from 1987 to 1991 and from 1995 to 2001. Fish biomass increased in the reserve by 27.2%. Trap and gillnet catches outside the reserve increased 26.9% by 2001. The Apo reserve was protected from 1982 to 2001. Total catch of major fish families was significantly higher after (19852001) than before (1981) reserve establishment at Apo, increasing 41.3% between 1981 and 19982001. These experiments, plus spillover evidence, suggest that marine reserves may help maintain, or even enhance, local fishery yields in the long-term.
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