Evaluating the comparative biological effectiveness of fully and partially protected marine areas (systematic review)


Marine Protected Areas (MPAs) encompass a range of protection levels, from fully protected no-take areas to restriction of only particular activities, gear types, user groups, target species or extraction periods. We synthesized the results of empirical studies that compared partially protected areas (PPA) to (i) no-take marine reserves (NTR) and (ii) to open access areas (Open), to assess the potential benefits of different levels of protection for fish and invertebrate populations.


A systematic search for relevant articles used terms describing MPAs, the biota (e.g. fish, invertebrates) and measures (e.g. density, biomass) of interest. Articles were examined for relevance using specified inclusion criteria. Included articles were appraised critically; the influence of studies whose effect of protection was identified to be confounded by habitat was examined by running a sensitivity analysis parallel to the main analysis that included all studies. Random effect meta-analysis on ln-transformed response ratios was used to examine the response to protection. Subgroup analyses and meta-regression were used to explore variation in effectiveness in relation to MPA and species covariates.


Synthesis of available evidence suggests that while PPAs resulted in higher values of biological metrics (density and biomass) than unprotected areas, greatest benefits were apparent in NTR areas when NTRs and PPAs were compared. For fish, the positive response to protection, whether full or partial protection, was primarily driven by targeted fish species. Although positive benefits were also apparent in non-target fish species, the results were more variable, perhaps because of fewer studies focusing on this group. Invertebrate studies were underrepresented and those available focused mainly on scallops, lobsters and sea urchins. Among the targeted species groups, benefits from partial protection relative to fished areas were highest for scallops, whereas benefits from full relative to partial protection were highest for lobsters. The examination of fish and invertebrate response to protection in terms of species richness and length was hampered by small sample sizes. There was significant variability in the magnitude of response to protection among the MPAs included in this study. The factors determining such variation were generally unclear although the size and protection regime of the PPA explained some of this variability.


The available evidence suggests that no-take reserves provide some benefit over less protected areas, nevertheless the significant ecological effects of partially protected areas relative to open access areas suggest that partially protected areas are a valuable spatial management tool particularly in areas where exclusion of all extractive activities is not a socio-economically and politically viable option.


Marine protected areas, Protection level, Fish, Invertebrates, Exploitation status, MPA design, Weighted meta-analysis


Only in the last decade has there been recognition that marine ecosystems worldwide are suffering massive and acute declines in biodiversity and irreparable alterations to ecosystem functioning (Boersma and Parrish, 1999; Millennium Ecosystem Assessment, 2005). Marine protected areas (MPAs) and other forms of marine spatial closures are increasingly common components of management programmes for living marine resources (NRC, 2001). The use of MPAs has been primarily advocated for protection of sensitive marine habitats and associated species (Roberts et al., 2001; Willis et al., 2003). Increasingly, these management tools have been proposed and implemented for use in achieving traditional fishery management goals, for limiting by-catches, and for increasing biomass in adjacent fished areas (Horwood et al., 1998; Piet and Rijnsdorp, 1998; Frank et al., 2000; Gell and Roberts, 2003; Sissenwine and Murawski, 2004). By protecting defined areas, including both resident species and their biophysical environments, MPAs offer an ecosystem-based approach to conservation or fisheries management, which is distinct from the traditional focus on single species conservation or management (Browman and Stergiou, 2004; Sissenwine and Murawski, 2004).

Various types of MPAs exist, all of which can be defined based mainly upon the level of protection and their primary goals. Some MPAs such as no-take marine reserves, prohibit all extractive and damaging anthropogenic activities, with the aim of protecting individual features of the marine environment, as well as restoring or maintaining the natural ecological balance within the ecosystem. Alternatively, multiple-use marine areas seek a balance between biodiversity protection and continued human use. Despite the beneficial effects of marine reserves for enhancing biomass and density of exploited species within reserves (Garcia-Rubies and Zabala, 1990; Garcia-Charton et al., 2004; Guidetti et al., 2005), rehabilitating community structure (Castilla, 1999; Shears and Babcock, 2002), enhancing reproductive output (Planes et al., 2000; Goni et al., 2003) and biomass exportation through adult migration (Chapman and Kramer 1999; Gell and Roberts, 2003), prohibiting all extractive activities in certain areas can have socio-economic costs. Indeed, even if reserves benefit fisheries (e.g. higher revenue per unit effort in the vicinity of the MPA boundary for haddock fishery, (Murawski et al., 2005)), local fishers may be negatively affected by the loss of fishing grounds, decreased catches and increased travelling time, at least in the short-term (Fiske, 1992). Consequently, marine reserves may face strong opposition by extractive users, making the process of reserve implementation and subsequent enforcement difficult. MPAs imparting partial protection from certain types of fishing are often advocated by groups with direct fishing interests and promoted as a ‘compromise’ solution allowing both protection and fishing (Denny and Babcock, 2004).

Ecological effects of MPAs are typically measured in terms of changes in biomass, abundance, species richness and body size (age) of species that occur within and outside the protected area (Pelletier et al., 2005). There is some evidence that the response of a species to protection depends, in part, on its life-history parameters (Blyth-Skyrme et al., 2006). For example, species that demonstrate a positive and rapid response to protection are often relatively sedentary and spend much of their life in the MPA (Boersma and Parrish, 1999; Murawski et al., 2000; Tawake et al., 2001). In contrast, for species of greater mobility or that utilize a variety of habitats, there is some debate over whether MPAs would be an effective conservation measure (Murawski et al., 2000; Kaiser, 2005), and what size MPA is required to achieve effective conservation of fish stocks (Mangel, 2000; Halpern, 2003; Claudet et al., 2008). In addition, characteristics of MPAs such as age (years since establishment), location, enforcement, regulation, size, distance from other protected areas have often been invoked as potential sources of heterogeneity in the response of marine assemblages to protection (Cote et al., 2001; Halpern, 2003; Halpern and Warner, 2002; Micheli et al., 2004; Guidetti et al., 2008).

While there have been numerous reviews of the effects of marine reserves on target and non-target species (Roberts and Polunin, 1991; Cote et al., 2001; Fraschetti et al., 2002; Halpern, 2003; Ojeda-Martinez et al., 2007; Claudet et al., 2008; Garcia- Charton et al., 2008; Lester et al., 2009), only one review examined the efficacy of partially protected MPAs to date (Lester and Halpern, 2008) and none of these reviews were done systematically (but see Stewart et al., 2008). Whereas the systematic review by Stewart et al. (2008) examined the impacts of temperate zone no-take areas on biological measures of marine biota, the systematic review to be undertaken will encompass a global synthesis of studies that have examined the efficacy of MPAs that confer varying levels of protection from extractive activities. Data on the life-history traits and ecological parameters of the reported species will be extracted and if correlations between effects on the response variable (e.g. fish biomass or abundance) and species characteristics (e.g. maximum body size, mobility) can be determined this may enable us to generate predictions about the response of particular species to spatial management measures.