Title
Review of the Benefits of No-Take Zones: A Report to the Wildlife Conservation Society
Author(s)
Craig Dahlgren
Published
2014
Abstract
Faced with overfishing, ecosystem phase shifts, and other declines in the condition or health of the marine environment, marine resource managers are increasingly turning to ecosystem-based approaches to management, including the use of marine protected areas (MPAs). MPAs are designated expanses of sea where some or all uses of marine resources are restricted to enhance the management or conservation of marine resources. MPAs may be created for a variety of purposes – fisheries management, biodiversity conservation, recreational uses, or to address the conservation needs of sensitive species or habitats. As such, they may be created and administered by a number of natural resource management authorities and under separate pieces of legislation in the same country and also under quite variable scenarios in different countries. MPAs worldwide have a wide range of restricted and permitted uses and are assigned a variety of different names – parks, sanctuaries, reserves, refuges – without much consistency in what management regimes actually apply in these areas. Increasingly, MPAs are divided into zones where different levels of protection are conferred. MPAs or zones within MPAs that have been shown to have the greatest positive impact on the resources within them are ones in which resource extraction, such as fishing, is prohibited. These areas go by many different names but are commonly referred to in the scientific literature as “no-take zones” or “fully protected” reserves.
Over the past 10-15 years, a tremendous number of studies have been conducted on the use of no-take zones for providing an abundance of benefits. The most commonly reported benefits from no-take zones around the world relate to their ability to conserve populations of exploited species. Evidence for these benefits is found in increases in the density, biomass per unit area, or individual sizes of various fishery species. In Belize and elsewhere in the Caribbean, there have been documented cases of improvements to conch, lobster and fish populations within no-take zones. Recovery of exploited species within notake zones as opposed to fished areas may take as little as 1-6 years, but full recovery of populations to near-pristine levels may take decades.
These changes may have important implications for conserving populations of target species. For example, the number of eggs that female fish produce increases exponentially with size, so more abundant populations of larger fish within no-take zones can increase reproduction by orders of magnitude over unprotected areas. Similarly, because fish in no-take zones survive to older ages and larvae hatched from eggs spawned from older and larger individuals have a greater chance of survival and higher growth rates, fish spawned in no-take zones have a greater probability of reaching juvenile stages. Increases in the size of males can also increase reproductive output of crustaceans such as the Caribbean spiny lobster, as larger males are more likely to successfully reproduce and increase the number of fertilized eggs brooded by females. For fishes that change sex from female to male, such as parrotfishes and many grouper species, the conservation benefits within notake zones include preserving natural sex ratios that can become skewed towards females in fished populations and cause females to change to males at smaller sizes, potentially reducing reproductive output. Finally, because fishing selectively removes some of the more aggressive and faster-growing individuals from populations, characteristics that have a genetic component, fishing selectively removes some of the fittest individuals from the population and, in so doing, may exert selective pressures on the evolution of species. Preserving these beneficial traits within no-take zones may maintain the genetic diversity of species.
The recovery of populations in no-take zones has important implications for fisheries for target species outside of these zones. No-take zones can support fisheries in two ways. The first is called the “recruitment effect,” whereby the increase in larvae spawned in no-take zones supports fisheries outside them, as larvae are carried by currents to fished areas where they recruit and replenish populations accessible to fishers. Recent advances in determining where larvae are spawned and where they recruit to juvenile populations indicate that no-take zones contribute a disproportionate amount of larvae to themselves (further increasing populations there) and fished zones. The extent to which this effect occurs in a location, however, depends on ocean currents, larval behavior and the time that larvae spend in the plankton.
The second manner in which no-take zones can support fisheries is through the “spillover effect,” whereby juveniles or adults from a reserve leave the reserve in response to crowding, expanding home range size as they grow, or other factors. This effect has been demonstrated in several ways and may be evident as a density gradient in populations where densities decrease with distance away from no-take zones; a gradient in catch per unit effort or catch per unit area that decreases with distance from a no-take zone; or tagging fish within a no-take zone and examining catches outside the no-take zone. The spatial extent of the spillover effect may depend on factors that influence movement (e.g., how home range size varies with size and density, agonistic behavior) of key species and the location of no-take zone boundaries within a seascape, but it generally occurs over distances of less than a kilometer from no-take zone boundaries.
The recovery of target species within no-take zones also has significant implications for various ecosystem properties. Because many target species are becoming scarce in fished areas, the recovery of their populations in no-take zones can enhance biodiversity of a marine ecosystem. No-take zones also eliminate bycatch within their boundaries, preserving stocks of many non-target species and preventing habitat damage from fishing gears. Increases in populations of target and bycatch species can also have cascading effects throughout the ecosystem through trophic or competitive interactions. Because many target species play an important ecological role as predators or grazers, increases in their numbers impact populations of their prey species, and even the species that these prey feed on. As a result, whole food webs can be affected. This can be particularly important in coral reef systems where the delicate balance between corals and macroalgae can be influenced by key grazers like parrotfish and urchins. Studies have shown that ecosystem processes responsible for maintaining healthy reefs may be increased in no-take zones, leading to less macroalgae, more coral recruitment, and healthier reefs. This may improve the resilience of reef ecosystems to impacts such as climate change and possibly the spread of invasive species such as lionfish. Further research is needed, however, to gain a better understanding of the roles of no-take zones in addressing these impacts.
From the human side of no-take zones, both the spillover and recruitment effects can benefit fisheries by promoting sustainable yields, buffering against the uncertainty that plagues traditional fisheries management, and increasing fishery yields and profits in many cases. No-take zones may also benefit recreational anglers by supporting trophy fisheries, as larger fish from the no-take zone spill over into fished areas. No-take zones can also support tourism, particularly for snorkelers and divers who are willing to pay more to visit healthier reefs with more abundant and larger fish and other sea life. No-take zones may also be used to reduce conflicts among fishers, dive operators, and other user groups whose use of resources may not be compatible. Because of their potential to reduce impacts towards a “pristine” marine ecosystem, no-take zones also have value for research and education and provide opportunities that are not available elsewhere. While there may be short-term costs to creating no-take zones, the long-term benefits to fisheries, tourism, and other activities can be significant.
Whether catch-and-release fishing should be permitted in no-take zones is the subject of much debate. A review of the literature on catch-and-release fishing shows that, while the majority of fish may be released alive, post-release survival is variable, depending on the type of fishing (e.g., flats fishing versus bottom fishing), angling and handling practices, tackle used, and the presence of predators likely to feed on released fish. Furthermore, injuries and stress resulting from catch-and-release angling may alter behavior and inhibit growth and reproduction of fish. Reviews specifically addressing whether catch-and-release angling should be allowed in no-take zones agree that this form of fishing can have negative impacts on populations, and that more research is needed to understand these impacts; however, they arrive at different conclusions as to whether or not the practice should be allowed. Based on all considerations, it is suggested here that well-regulated catch-and-release angling could be allowed in some, but not all, no-take zones in Belize, based on certain conditions, and that regulations should restrict the number of permits issued for an area, and set requirements on gear types and use and best practices for landing, handling and releasing fish.
While no-take zones can provide a wide range of benefits for conservation, fisheries, tourism, research and education, and ecosystem protection, specific benefits generated may vary among no-take zones. This variability can result from differences in the size, shape, configuration within a seascape, and proximity to other no-take zones, as well as the characteristics of the species being protected, characteristics of the fishery outside of notake zones, and the level of compliance with no-take zone restrictions. Basic design principles can be followed, however, to produce an effective network of no-take zones, and some benefits may be increased by incorporating specific design characteristics. Regardless of the design, however, the rules and regulations of the no-take zone must be respected. Voluntary compliance can be increased through engagement of stakeholders in the designation process and implementation of no-take zones, as well as clearly marking the zone boundaries and communicating rules and regulations. Effective enforcement is also necessary.
Belize is currently in the process of expanding its national network of no-take zones from a total of approximately 3% of its marine territory to 10%. Because terms such as “no-take zone” or “fully protected area” may have a negative connotation for resources users concerned about being restricted from these areas, and in order to better reflect the overall objective of enhancing benefits to fisheries and biodiversity, these areas are being referred to as “replenishment zones.”
In taking lessons from the examples presented in this report, Belize’s expanded no-take, or “replenishment,” zone network should provide increased benefits for the conservation of target species, fisheries management, preservation of ecosystem function, as well as to the livelihoods and well-being of Belizeans.
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