Title
Recovery of functional groups and trophic relationships in tropical fisheries closures
Author(s)
McClanahan, T. R.
Published
2014
Publisher
Marine Ecology Progress Series
Abstract
Ecological changes associated with Kenya's fisheries closures were examined using a space-for-time substitution chronosequence based on 5 fisheries closures that ranged in age since closure from 5 to 41 yr. The chronosequence allowed estimates of the rates of change and recovery of key ecological processes and functional groups. I asked if ∼35 yr was sufficient time for the ecosystem to recover and stabilize from fishing effects. Total consumer biomass peaked at 15-20 yr, but the magnitude and time scale of other functional group responses varied and were not always predictable based on assumed successional rates of recovery (i.e. plants > herbivore > carnivore > piscivore). For example, piscivore recovery was minor and variable while the biomass of herbivorous fishes was slow and had not clearly stabilized by the end of the time series. In contrast, predation rates on sea urchins were a key process that increased slowly and sea urchin biomass declined to very low levels at ∼20 yr of closure. Against predictions, total herbivory estimates and fleshy erect algae and hard coral cover did not change with the age of the closures, indicating the importance of multiple types of herbivores and climate disturbances. For benthic cover groups, time since closure was a strong predictor (R2 > 0.50) for seagrass and red coralline algae, which increased over time, and sand and calcareous green algae, which declined over time. These changes were complete on the 20 to 30 yr time scale. Consequently, processes were generally slow and functional group recovery was not fully complete by ∼35 yr of closure. I speculate that recovery processes and times in these closures are likely to be influenced by human disturbances in the surrounding seascape and that permanent, old, and large closures are needed to represent fully restored tropical reef lagoon ecosystems. © 2014 Inter-Research.
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PUB15239