Connectivity in reef fish assemblages between seagrass and coral reef habitats

Abstract

Coral reefs and seagrass beds form extensive shallow-water habitats, but few reports have assessed the extent to which fishes on coral reefs are segregated from or integrated with fish from seagrass habitats. To investigate this, we used visual census surveys to survey reef fish assemblages in 3 habitat types: (1) seagrass, (2) transition areas between seagrass and coral reef and (3) coral reefs, at 8 locations in an Indonesian marine protected area. Based on the density of juveniles and adults, 66 of the 212 fish species recorded were classified into 4 ecological groups: seagrass residents, generalists, nursery species and coral residents. Coral residents and nursery species were found in reef and transition habitats, seagrass residents in seagrass beds and transition habitats, and generalists showed a gradual decrease in density from coral reef to seagrass beds. In terms of reef fish density, seagrass residents and nursery species accounted for 21 and 17%, respectively, of the 66 species classified into ecological groups. Habitat segregation among life stages of some nursery species, where adults were found in a coral habitat and juveniles in seagrass, was indicative of ontogenetic shifts from seagrass to coral habitat. Segregation in the distribution of feeding groups among habitat types also occurred, with nocturnal piscivores and diurnal zoobenthivores mostly found in coral and transition habitats, while nocturnal zoobenthivores, herbivores and diurnal piscivores were mostly found in seagrass and transition habitats. These patterns differ from those reported in similar habitat types elsewhere, but overall the results support previous findings, i.e. that optimisation of predatory and resource competition mechanisms may be responsible for habitat segregation of fish species, life stages and feeding groups.

Seascape-scale trophic links for fish on inshore coral reefs

“…As in the Caribbean Sea (reviewed by Grober-Dunsmore et al 2009;Boström et al 2011), the density of adult fish on inshore coral reefs is positively influenced by connectivity with adjacent seagrass (e.g., Dorenbosch et al 2005;Unsworth et al 2008;Campbell et al 2011;Olds et al 2014) and mangrove habitats (e.g., Nagelkerken 2007;Berkström et al 2012;Olds et al 2013).…”

The Great Barrier Reef World Heritage Area seagrasses: Managing this iconic Australian ecosystem resource for the future

“…They provide critical habitats for juvenile fish (Vasconcelos et al, 2011;Nagelkerken et al, 2013) and crustaceans (Loneragan et al, 1997) during their nursery phases and food for dugong and turtles. The most obvious value of seagrass to juveniles is the feeding and refuge habitats they provide, but just as important is the role of seagrass as a connecting habitat between other components of the coastal ecosystem mosaic (Campbell et al, 2011;Nagelkerken et al, 2013). At local scales intertidal and shallow sub tidal seagrass meadows occur between feeding areas in the mangroves forests that fringe tropical estuaries and provide the low tide refuges required by juveniles when mangroves are unavailable (Sheaves, 2005).…”

Changes in a coral reef fishery along a gradient of fishing pressure in an Indonesian marine protected area

“…Each village has a different number of sub-villages and each village has local fishing grounds, where fishers work and bring their daily catch to the main landing sites on Karimunjawa Island for distribution to markets inside and outside the national park. Fishing grounds included areas of nearshore coral reef to maximum depths of 30 m and areas of nearshore mixed reef-seagrass and seagrass habitats (Campbell et al, 2011). The surveys of fish harvested in the present study included fish caught for market distribution and does not include the 5-10% of catch used for direct household consumption.…”