Recovery trajectories of coral reef fish assemblages within Kenyan marine protected areas

Abstract

The size, density and biomass of coral reef fish in 4 fully closed marine protected areas (MPAs) with different ages were studied over a 17 yr period. Space-for-time substitution samples were available for a period of 4 yr before, and 36 yr after the closure. Both the height of the size structure graph (which is a value of overall abundance-biomass) and the assemblage biomass graph are convex polynomials with a maximum biomass of 1200 kg ha -1 at 22 yr. This suggests that full recovery of coral reef fish assemblages in terms of abundance-biomass is considerably longer than generally believed. Beyond 25 yr, there can be a small loss in biomass, which we suggest is due to reduced net primary production associated with the increased abundance of calcifying algae attributable to intense grazing. Size spectra slopes were variable at all times, changed quickly, and were probably influenced by local environmental conditions, which made concise predictions for equilibrium coral reef size structure rather difficult.KEY WORDS: Biomass · Recovery · Marine protected areas · Calcifying algae · Fish growth · Size spectra Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 294: [241][242][243][244][245][246][247][248] 2005 quences with different initial starting points of management in order to test for general patterns that are not site-or timerestricted.With increasing calls for ecosystem approaches to fisheries management (Link 2002, Browman & Stergiou 2004, Pikitch et al. 2004, the use of aggregated techniques (such as size-based approaches to analyze assemblage data) are becoming more common . As maximum size is correlated with many other life-history traits, resulting in larger fish being more vulnerable to exploitation (Jennings et al. 1999, Denny et al. 2002 and because larger fish are generally targeted before smaller fish (Pauly et al. 1998), size is proving to be a useful way to assess multispecies fisheries (Bianchi et al. 2000, Dulvy et al. 2004, Graham et al. 2005. Increasing evidence of species-level (Watson and Ormond 1994, Graham et al. 2003) and aggregated size-based (Dulvy et al. 2004) indirect interactions within coral reef fish assemblages further suggest that recovery trajectories in these ecosystems should be assessed at the assemblage level.This study examines the size structure and biomass of coral reef fishes in Kenyan coral reefs by examining 4 fully closed MPAs that vary in their time of establishment (from 1968 to 1991) with data that are available from 4 yr prior to and 36 yr after closed-area management (see Table 1). The study sites were examined between 1987 and 2004, and repeatedly sampled so that a 40 yr chronosequence of management can be patched together from this sampling and differences in the starting dates for closed-area management. Here, we focus on the recovery of biomass and size structure of the total fish population as a function of the age of the closedarea protection to determine if there are consistent and general patt...

Avoiding conflicts and protecting coral reefs: customary management benefits marine habitats and fish biomass

“…However, the positive correlation between fish biomass and the number of fishing gears prohibited also suggests that gear restrictions are having a direct effect by reducing fishing pressure. Reef fish biomass can be ten-fold greater in marine protected areas within ten years of closure when compared to adjacent heavily fished areas (McClanahan and Graham, 2005;Russ et al, 2005;Aburto-Oropeza et al, 2011). Similarly, in a reef fishery in Tanzania, the banning of dynamite, cyanide and the use of small-mesh seine nets that are deployed in a similar manner to muroami nets on Pulau Weh, also resulted in an increased abundance of reef fish and biomass of some fish families (Tyler et al, 2011).…”

Effects of rotational closure on coral reef fishes in Waikiki-Diamond Head Fishery Management Area, Oahu, Hawaii

“…They presumed that this was a consequence of delayed recruitment effects and that, in the first few years of protection, the fish stocks were dominated by very young fishes which do not accumulate as much biomass as fishes aged from 2 to 4 yr. While it might be possible to increase closure benefits of a rotational strategy by extending the duration of the closed period beyond the 1 or 2 yr implemented at Waikiki, it is important to recognize that full recovery in terms of ecological function, community structure, and total biomass, particularly of large predatory fishes, is likely to take 10 or more years following cessation of fishing (McClanahan 2000, McClanahan & Arthur 2001, McClanahan & Graham 2005. Large fishes are not only prime fishery targets, but are also particularly important in terms of community fecundity (Sadovy 1996, Birkeland & Dayton 2005, ecological role (Friedlander & DeMartini 2002, DeMartini et al 2005 and their value to marine tourism (Williams & Polunin 2000).…”

Factors Influencing Adaptive Marine Governance in a Developing Country Context: a Case Study of Southern Kenya

“…Another management tool for controlling extraction pressure is the no-take zone or marine park. No-take zones can lead to increased abundance, biomass, and species richness (McClanahan and Graham 2005) and protect sensitive species, which can include functional key-stone species and long-lived individuals with high fecundity (McClanahan 2000). They can thereby contribute to ecological resilience, although see Graham et al 2008 for a critical take on the performance of no-take MPAs in the context of climate change.…”