Effective protection of fish on inshore coral reefs depends on the scale of mangrove - Reef connectivity

Abstract

Connectivity is an important consideration in conservation, but is rarely quantified when assessing marine reserve performance. Mangrove-reef connectivity is known to enhance reserve effectiveness when habitats are close together (< 250 m apart). Coral reefs are, however, often farther from mangroves, making it difficult to integrate mangrove-reef connectivity into conservation more widely. To determine if connectivity affects reserve performance beyond 250 m, we examined effects on reef fish in Hervey Bay, Queensland, Australia. Reserves affected fish assemblages and enhanced the abundances of harvested species and key functional groups on reefs within 500 m of mangroves (about 10 times greater inside reserves), but not on isolated reefs. Connectivity can affect reserve performance over broader distances than previously shown. We suggest that connectivity effects on inshore reef fish may simply be amplified on reefs located closest to adjacent mangroves, provided those reefs are within the migratory capabilities of fish. Mangrove-reef connectivity should be viewed as an important conservation target and may be broadly incorporated into reserve design by prioritizing the protection of seascapes where mangroves and reefs are closest.