Untangling Natural Seascape Variation from Marine Reserve Effects Using a Landscape Approach

Abstract

Distinguishing management effects from the inherent variability in a system is a key consideration in assessing reserve efficacy. Here, we demonstrate how seascape heterogeneity, defined as the spatial configuration and composition of coral reef habitats, can mask our ability to discern reserve effects. We then test the application of a landscape approach, utilizing advances in benthic habitat mapping and GIS techniques, to quantify this heterogeneity and alleviate the confounding influence during reserve assessment. Seascape metrics were quantified at multiple spatial scales using a combination of spatial image analysis and in situ surveys at 87 patch reef sites in Glover's Reef Lagoon, Belize, within and outside a marine reserve enforced since 1998. Patch reef sites were then clustered into classes sharing similar seascape attributes using metrics that correlated significantly to observed variations in both fish and coral communities. When the efficacy of the marine reserve was assessed without including landscape attributes, no reserve effects were detected in the diversity and abundance of fish and coral communities, despite 10 years of management protection. However, grouping sites based on landscape attributes revealed significant reserve effects between site classes. Fish had higher total biomass (1.5×) and commercially important biomass (1.75×) inside the reserve and coral cover was 1.8 times greater inside the reserve, though direction and degree of response varied by seascape class. Our findings show that the application of a landscape classification approach vastly improves our ability to evaluate the efficacy of marine reserves by controlling for confounding effects of seascape heterogeneity and suggests that landscape heterogeneity should be considered in future reserve design.

Monitoring fish in California Channel Islands marine protected areas with a remotely operated vehicle: the first five years

“…In addition, factors other than protection need to be studied to elucidate variability. Confounding factors can obscure the response to protection (Huntington et al 2010).…”

Tailoring Ecological Monitoring to Individual Marine Reserves: Comparing Longline to Hook‐and‐Line Gear to Monitor Fish Species

“…While numerous studies exist to guide marine reserve placement and implementation, comparatively few studies have been conducted to inform best practices for how to evaluate the performance of these reserves (but see Underwood 1994;Lincoln-Smith et al 2006;Claudet and Guidetti 2010;Huntington et al 2010). Marine reserves within the northeastern Pacific Ocean vary greatly in their physical and ecological characteristics as well as their socioeconomic contexts, making it unlikely that a single study design or survey tool will be applicable to all of these areas (Fraschetti et al 2002).…”

“…These management areas include mandates to establish robust and appropriate long-term surveys to evaluate changes in the marine community within these managed areas over time. At this early stage of reserve implementation, it is timely to validate whether survey methods are appropriately tailored to the marine communities most likely to show responses to this management strategy-namely, species targeted by local fisheries (Molloy et al 2009;Huntington et al 2010;Claudet et al 2010).…”

Untitled

“…Given the relatively small size of the patch reefs surveyed in the study (Table 1), dive teams of 2-4 divers were able to reliably assess the species richness of the entire patch reef within a 50-min dive. Reef size, defined as the two-dimensional reef area, was measured from high-resolution (50 cm) multiband satellite imagery for each patch reef (Huntington et al 2010). Areas were log-transformed to achieve normality.…”