An analysis of indicators for the detection of effects of marine reserve protection on fish communities

Abstract

We investigated the effects of marine reserve protection on fish and benthic communities at Glover's Reef Marine Reserve, Belize, using a broad suite of indicators. Responses of fish species to protection were highly variable, and therefore indicators calculated at the fish community level were ambiguous. According to 11 of 13 community-level indicators, sites located within the no-take zone fared more poorly over time than did sites in the surrounding fished area. However, we were able to detect positive reserve effects using a newly-proposed pair of indicators, which take into account spatial distribution of different species at the time of the no-take zone implementation. These indicators showed that species subject to low fishing pressure increased inside and to a lesser extent outside the no-take zone, while species subject to higher levels of fishing pressure increased in the no-take zone but decreased in the fished area. Indicators of changes in the fish community were not correlated with those related to the benthic community, and we suggest that indicators be carefully selected to match management objectives. We also find that positive reserve effects based on present-day data (e.g., higher abundances of commercial species inside the no-take zone versus outside) were often not associated with increases in fish densities over time, and suggest caution when interpreting abundance patterns in the absence of historical data. We recommend that similar studies be carried out at a variety of reserve sites, to test our proposed indicators and increase our understanding of community-level responses to fisheries closures.