Spatial habitat partitioning enables coexistence of three Gobiidae species in estuarine environments

This study examines resource partitioning (feeding morphology, diet and habitat partitioning) among three gobiid species, the Knysna sandgoby Psammogobius knysnaensis, the prison goby Caffrogobius gilchristi and the river goby Glossogobius callidus, within an estuarine environment. The findings revealed distinct habitat preferences: P. knysnaensis predominantly occupied the sandy mouth of the estuary, C. gilchristi favoured the lower reaches and G. callidus was abundant in the upper reaches. Principal component analysis of feeding morphological traits indicated significant overlap between the feeding morphology of C. gilchristi and G. callidus. Although the two species showed overlapping morphological traits, they exhibited distinct diets, influenced by differences in prey availability within their feeding environments. Cyclopoids, which were widespread throughout the estuary, were a common dietary item for both species. Psammogobius knysnaensis and C. gilchristi had overlapping diets, but each species appeared to dominate in different habitats. This study highlights that habitat partitioning drives resource partitioning among the three species, enabling their coexistence in a dynamic estuarine ecosystem.