MEPS 308:79-89 (2006)  -  doi:10.3354/meps308079

ABSTRACT: Segregation of resources is supposed to be a mechanism for coexistence of species and/or life stages when resources are limiting and competition between species occurs. In seagrass beds, fish species richness is lower than on coral reefs, but food abundance is in general higher. In this case, food segregation may not occur. Here, the null hypothesis is tested that species show no segregation in feeding with respect to time, space and diet. The structure of the food web in a tropical seagrass bed revealed that the seagrass fish community consisted of species feeding at 3 trophic levels: (1) herbivores, (2) omnivores, zoobenthivores and zooplanktivores, and (3) piscivores. The data suggest that herbivores partitioned food by specialising on seagrass epiphytes, seagrass leaves or macroalgae from the seagrass bed, with 1 species presumably feeding in adjacent mangroves. Fishes at the second trophic level showed temporal segregation in feeding habits between fish families, while species within families showed segregation in food type and source. At the third trophic level, 1 piscivorous species was found. The majority of fish species showed a very narrow diet breadth with a significant segregation in resource-use. The null hypothesis was rejected since feeding segregation was not random for time, space and diet, viz. feeding time and diet (33.3%), diet only (25.5%), time, habitat and diet (15.2%), habitat and diet (13.4%), time only (3.5%) and habitat only (2.6%). Segregation in resource use was present along 1 to 3 resource axes simultaneously, which could support coexistence of species that favour comparable food types if food were limiting.

KEY WORDS: Resource segregation · Diet composition · Stable isotopes · Food web · Coastal habitats