Spatial zoning to conserve fish species with complex life cycles in estuaries

Abstract

Fish conservation in estuaries is complex because there are diverse social values and interests associated with estuarine ecosystems and multiple ecological processes (e.g., nursery, connectivity, and population dynamics). Furthermore, ontogenetic shift has an important role in determining fish habitat use (e.g. pelagic vs benthic environments), and consequently, critical implications for conservation. Here, we develop a prioritisation approach to create conservation zones in an estuarine system that considers fishery costs while also integrating pelagic and benthic habitats for different life history stages (from eggs to adults), and multiple conservation objectives. We applied our approach to the whitemouth croaker Micropogonias furnieri in the Patos Lagoon estuary (Brazil) and tested four scenarios based on different objectives, zone types and targets. In this study, we used Marxan and Marxan with Zones and accounted for 41 conservation features (including habitat type, vegetation and seasonal distribution of whitemouth croaker within the estuary). Overall, we found two important results. First, spatial priorities for the no-take and partially protected zones did not change substantially and were very robust to variation in uncertain parameters. Second, an integrated conservation plan with multiple zones requires less area to be designated as no-take zone than a traditional conservation plan with a single zone. A well-designed conservation plan based on multiple life stages may help to ensure the recruitment, persistence and management of important estuarine resources.