The conservation implications of spatial and temporal variability in the diurnal use of Bahamian tidal mangrove creeks by transient predatory fishes

Abstract

Mangrove creeks have a range of functional roles in tropical seascapes, but their use as feeding and refuge areas for commercially and ecologically important transient predators is poorly understood. This study used video cameras to investigate the diurnal use of three Bahamian mangrove creeks by transient predators during a 2-month period. More than 500 fishes from 10 species were recorded, including elasmobranchs, reef-associated fishes, and nearshore specialists. A multivariate analysis indicated that movement of the transient predator assemblage was not significantly linked to any abiotic variable and did not vary among creeks. Generalized linear mixed-effects models of the four most abundant transient predators demonstrated species-specific variations in creek use. Sightings of Caranx ruber and Negaprion brevirostris varied significantly among the three creeks. Furthermore, C. ruber was seen most frequently close to high tide, while N. brevirostris was seen more frequently with increasing time since sunrise and during higher tidal ranges. Sphyraena barracuda and Tylosurus crocodilus were seen most frequently just after low tide. All three creeks appear to be functionally important for transient predators, but these species exhibit considerable spatio-temporal variability in how they use this habitat. Mangrove creeks are threatened by a range of anthropogenic stressors, and are frequently a target of conservation initiatives. The species-specific spatial variability in creek use demonstrates that simply including representative creeks in marine protected areas could exclude functionally important areas. Furthermore, development that alters tidal cycles in creeks is likely to have significant impacts on transient predators, and underscores the need for restoration and conservation of hydrological flow.