Evaluating the energetic value and structural contributions of mangroves and seagrasses to local fish populations: The importance of habitat connectivity

Red mangroves provide structurally complex refuges for fishes hiding from larger, visual predators. However, the amount of food available to fishes within the mangroves has been incompletely documented. This study used a combination of visual and video censuses, caging experiments, invertebrate tethering, and stomach content and stable isotope analysis to determine the extent to which fish utilize both mangrove and seagrass habitats as refuges and/or feeding sites. Fish species composition and density in the two habitats were found to shift significantly with time of day and distance from the mangrove. Caging studies indicated that infaunal densities were higher within the seagrass bed than within the mangrove proproots. Carbon signatures indicated a strong reliance of mangrove fish species on prey living in seagrass habitats. This suggests that mangrove-associated fish species forage over great distances to meet their nutritional needs, thus emphasizing the importance of habitat connectivity to mobile species.