Marine reserves and Seascape context shape fish assemblages in seagrass ecosystems

Abstract

Spatial properties of landscapes modify the abundance and diversity of most animal assemblages in ways that need to be understood to plan and implement conservation initiatives, and evaluate their effectiveness. Seascape context (i.e. the spatial arrangement of ecosystems) mediates the effects of reserves on fish abundance, species richness and ecological processes in shallow coral reef and mangrove ecosystems; however, it is unclear whether this interaction exerts similar effects on reserves in other ecosystems. This study used baited remote underwater video stations (BRUVS) to test for combined effects of seascape context and reserves on fish abundance in seagrass meadows in Moreton Bay, Queensland, Australia. We demonstrate that the composition of harvested fishes in seagrass meadows was different in reserves and fished areas. Specifically, in reserves there was enhanced abundance of exploited rabbitfish Siganus fuscescens, a functionally important herbivore in local seagrass meadows. These reserve effects are not influenced by the area of seagrass meadows or seascape context they occur in (i.e. their spatial proximity to other ecosystems or the ocean). However, seascape context was directly correlated with the spatial distribution of harvested rabbitfish and emperors Lethrinus spp., which were more abundant in seagrass meadows nearer to the open ocean. Our results show that reserves and seascape context can shape spatial patterns in the abundance of harvested fishes in seagrass meadows, and that these effects may be operating on different components of fish assemblages. Further empirical data on how and where seascape features modify reserve performance are critical for effective conservation in seagrass and related ecosystems.