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