No-Take Marine Reserves for Reef Fisheries and Ecosystem Management

Defense Date

6-2000

Document Type

Capstone

Degree Name

M.S. Marine Biology

First Advisor

Joshua Feingold

Second Advisor

Steven L. Miller

Abstract

Increased documentation and awareness of the decline of fisheries at a global scale is partly testament to the shortcomings of conventional management of catch and effort regulations, but also the difficulties of managing human activities in complex marine environments and open-access policies towards marine resource utilization. In high diversity tropical ecosystems like coral reefs, fisheries management is made even more problematic by the diversity and strength of interactions among species (eg. competition and predator-prey), the mobility and interconnectedness of organisms and their habitats, and the general paucity of information on even basic life history characteristics (eg. growth, recruitment and mortality). Additional challenges to sustainable fisheries include the diversity of species targeted, gears and methods used, fishing objectives, vulnerability of many species to even moderate levels of fishing, and generally poor enforcement and administrative capacity. All of these characteristics testify to the potential shortcomings of applying single-species models and complex catch and effort regulations in tropical multi-species fisheries. There is mounting evidence of the species and community-level effects that fishing can have on marine ecosystems like coral reefs. Besides the more obvious species-level effects on diversity, abundance, size, fecundity, and behavior of targeted species, several studies have shown the effects that fishing may have on non-targeted species, interactions among species, and habitat structure Such effects include not only the physical impacts caused by various types of fishing gears, but also potential changes in processes such as competition, predator-prey interactions, and even reef construction due to the non-selective nature of most fishing gears.

Marine reserves, also referred to as fishery replenishment zones, no-take zones or harvest refugia, are areas of the ocean closed to consumptive usage, especially fishing, and are the subject of this review. Marine reserves have sparked interest as an alternative or complement to current management regimes in shallow demersal environments such as coral reefs, but implementation has also been advanced in temperate and more offshore fishing grounds where previous management measures have not prevented the decline of fishery targets and habitat quality. The concept of marine reserves is simple, yet not widely accepted because of certain human belief patterns (eg. the inexhaustibility paradigm and burden of proof) and open-access policies: to afford protection to habitats and species by eliminating (m theory) fishing mortality and the physical impacts caused by fishing gear in designated spatial refuges. Marine reserves, however, also present other opportunities heretofore not possible or difficult because of the pervasiveness of fishing: scientific opportunities to better understand fishing at several scales of biological organization, enhanced economic and recreational opportunities, and protection of ecosystem structure and function. At the time of this writing, no less than 50 empirical studies, mostly in tropical settings, have documented the beneficial effects of marine reserves on targeted species (eg. performance measures such as abundance and si2e being the most commonly measured), in addition to community ( eg. species composition) and process-level effects ( eg. reef construction), albeit fewer. These overwhelming lines of evidence lend support to the benefits expected from marine reserves in a relatively short period of time (1-3 years in some cases), especially for targeted species, and even in relatively small reserves. The potential benefits to fishers' catches through 'spillover' of larvae (via physical transport) and juveniles/ adults (via movement patterns). However, have been difficult to demonstrate unequivocally. The possible factors contributing to this scenario are the relatively small sizes of existing reserves (most on the order of a few Jan2 in area) relative to the great expanse of areas fished, the long history (m some cases centuries) of intense fishing in most coastal environments, and limited movement patterns of many reef-associated organisms. Other potential benefits of marine reserves, such as conservation of biodiversity and diversification of non-consumptive opportunities have been insufficiently documented.

Several criteria can be considered when attempting to implement marine reserves. Probably the most important is the objective(s) of the marine reserve in question, as any single reserve will not necessarily be beneficial to all species and all potential user groups. A major consideration to address is whether the protected area should be designed for biodiversity conservation or as a fishery management tool Arguments abound concerning whether these two objectives are compatible, but at the very least, such concerns may have implications for protected area design. Marine reserves are likely to be most successful when demersal (bottom-associated) species are targeted (as opposed to highly migratory species), cross-shelf habitats important for ontogenetic migrations are encompassed within reserve boundaries, and other human impacts (particularly those from land-based sources) are minimized. These considerations underlie the importance of conceptualizing networks of marine reserves, replicated and representative of biogeographic units (e.g. habitats and ecosystem types), linked by physical transport mechanisms, and encompassing broad enough areas so that fisheries on a broader, regional level may be supported. Although factors such as location, size, shape (volume to edge ratio) and spacing of marine reserve units are important, many of these criteria have only been evaluated from a theoretical or conceptual standpoint For areas with sufficient administrative and enforcement capacity, the application of catch and effort regulations should be continued to help minimize the probability of growth overfishing and other objectives sought by these policies. Although marine reserves offer an alternative and potentially successful fisheries management paradigm for reef environments, implementation of marine reserves alone will not be sufficient to address the underlying cause(s) of resource overexploitation, namely excess capacity, lack of satisfactory property rights, and increasing human population growth.

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