A network analysis of habitat connectivity for reef-associated fish to evaluate marine reserve placement

Movements by fish make important connections among habitat patches in coastal seascapes. Identification of movement patterns can help incorporate connectivity into conservation management. For this strategy to be successful,... [ view full abstract ]

Movements by fish make important connections among habitat patches in coastal seascapes. Identification of movement patterns can help incorporate connectivity into conservation management. For this strategy to be successful, however, we first need to develop reliable methods for determining key components of connectivity in seascapes. We evaluated the placement of reserves in Moreton Bay Marine Park, Queensland, in the context of habitat connectivity for fish associated with coral reefs. We used network analysis to identify key habitat mosaics and connections amongst mosaics, and to quantify how many are currently protected in reserves. Our analysis accounted for two scales of connectivity: 1. the spatial configuration of habitats within mosaics (reef-seagrass-mangrove habitats), an important aspect of diel fish movements, and 2. inter-mosaic movements by fish over longer periods. To represent a wide variety of mobility capabilities of fishes, we used the movement behaviours of the commercially and recreationally important fish species yellowfin bream (Acanthopagrus australis) and estuary cod (Epinephelus coioides). This multi-scale habitat connectivity analysis identified areas and connections that are likely to contribute most to habitat connectivity for fish. Sensitivity analyses showed that the model outputs were robust to assumptions about the frequency of movements over different distances among mosaics. And validity of the model was high – predicting fish diversity (abundance and richness) with a good fit. Of 29 mosaics, the ten most important accounted for 86% of the network. Only three of these ten mosaics are within reserves, and each of these three mosaics is only partly protected (< 50% by area in each case). Of the ten most important connections between mosaics (out of 406 possible connections), just one lies within a reserve. Fish connectivity is not well protected by the current reserves in Moreton Bay Marine Park. Habitat connectivity is one of a number of conservation criteria for managers; the approach used here provides valuable information for incorporating spatial and fish behavioural data into a multi-objective conservation plan.