Toward Pristine Biomass: Reef Fish Recovery in Coral Reef Marine Protected Areas in Kenya

Abstract

Identifying the rates of recovery of fish in no-take areas is fundamental to designing protected area networks, managing fisheries, estimating yields, identifying ecological interactions, and informing stakeholders about the outcomes of this management. Here we study the recovery of coral reef fishes through 37 years of protection using a space-for-time chronosequence of four marine national parks in Kenya. Using AIC model selection techniques, we assessed recovery trends using five ecologically meaningful production models: asymptotic, Ricker, logistic, linear, and exponential. There were clear recovery trends with time for species richness, total and size class density, and wet masses at the level of the taxonomic family. Species richness recovered rapidly to an asymptote at 10 years. The two main herbivorous families displayed differing responses to protection, scarids recovering rapidly, but then exhibiting some decline while acanthurids recovered more slowly and steadily throughout the study. Recovery of the two invertebrate-eating groups suggested competitive interactions over resources, with the labrids recovering more rapidly before a decline and the balistids demonstrating a slower logistic recovery. Remaining families displayed differing trends with time, with a general pattern of decline in smaller size classes or small-bodied species after an initial recovery, which suggests that some species- and size-related competitive and predatory control occurs in older closures. There appears to be an ecological succession of dominance with an initial rapid rise in labrids and scarids, followed by a slower rise in balistids and acanthurids, an associated decline in sea urchins, and an ultimate dominance in calcifying algae. Our results indicate that the unfished "equilibrium" biomass of the fish assemblage > 10 cm is 1100-1200 kg/ha, but these small parks (< 10 km2) are likely to underestimate pre-human influence values due to edge effects and the rarity of taxa with large area requirement, such as apex predators, including sharks.

Trajectories and magnitude of change in coral reef fish populations in Philippine marine reserves: a meta-analysis

“…Statistics are given in Table 3 previous analyses of the Philippine reserves (e.g., Alcala 2003, 2004;Maliao et al 2004;Russ et al 2005;Alcala et al 2005). This finding is also consistent with the results of previous assessment of reserves on coral reefs elsewhere (Friedlander et al 2003;Graham et al 2003;McClanahan et al 2007;Harborne et al 2008). Although at the outset it is tempting to attribute the higher density of exploited fishes in the reserves to the absence of fishing, it is conceivable that there are a multitude of factors that contribute to the observed disparity in fish density between reserves and the adjacent fished reefs.…”

Recovery of marine animal populations and ecosystems

“…Restoration of kelp along Korean coasts resulted in the complete recovery of macroalgal community structure and trophic food webs [16]. Studies in MPAs illustrate successional recovery of different community components (Figure 3c) as well as re-establishment of lost predatory interactions and food-web structure [14,15,68,69]. Moreover, significant increases occurred in secondary productivity, ecosystem stability and economic revenue from recreational diving in 48 MPAs and fisheries closures worldwide [22].…”

“…Restoration of water quality resulted in the return of >110 fish species to the Thames estuary (Figure 3b) [13] and the recovery of intertidal macroalgal communities from 1984 to 2006 after implementing sewage treatment in Bilbao, Spain [66]. Cessation of exploitation in marine protected areas (MPAs) around the world resulted in significant increases in species richness of fishes and invertebrates [15,22] and habitat restoration of oyster reefs has enhanced associated species diversity [67].…”

“…Clupeids, such as herring and sardines, have shown more rapid recovery within 5-10 years after depletion, whereas gadoids showed no, or slow, recovery within 15 years after depletion [20]. In a MPA, species richness of coral reef fishes reached a plateau after 10 years, whereas density peaked after 7-37 years depending on the life history [15]. After benthic trawling, slower-growing sponges and corals took up to 8 years to recover compared with <1 years for polychaetes [21].…”

“…Similarly, many coastal habitats, including wetlands, seagrass beds, mangrove and kelp forests, and oyster and coral reefs, have been severely reduced or degraded [2][3][4]6], yet partial recovery has been achieved in some regions in response to protection and pollution controls [3,13]. Restoration attempts at an ecosystem level have often been followed by the return and recovery of former species assemblages and ecosystem functions [13][14][15][16][17], but some ecosystems have remained in an altered state [18]. Such successes could serve as important guides for efforts to prevent further biodiversity loss and enhance future recoveries.…”