Distribution of fish among Avicennia and Sonneratia microhabitats in a tropical mangrove ecosystem in South China

Abstract

Mangrove structural complexity plays an important role in the way fish using their habitat. However, the effects of structural attributes on fish spatial distribution remain uncertain. In this study, we sampled fish at three easily identifiable microhabitats (i.e., vegetated area with both mangrove trees and pneumatophores, pneumatophore area without trees, and adjacent mudflat without trees and pneumatophores) within two sites dominated by Avicennia marina and Sonneratia apetala in a large estuarine system in South China from 2014 to 2015, and explored the fish community differences in these microhabitats. Our results showed that fish assemblages varied significantly among the three microhabitats, with distinct community assembly patterns between sites. At the Avicennia site, highest fish diversity was recorded at the mudflat, followed by the pneumatophore area and the vegetated area. In contrast, the opposite pattern was observed at the Sonneratia site. Fish size also differed significantly among microhabitats, with smaller fish presented in the vegetated areas. Within the same mangrove types, the height and biomass of pneumatophores as well as density of trees showed significant effects on the among-microhabitat variations of fish assemblages. Fish abundance was positively associated with pneumatophore height and negatively correlated with pneumatophore biomass at the Avicennia site. While at the Sonneratia site, it was positively correlated with pneumatophore biomass. We conclude that the spatial variations of fish community are highly correlated with the structural complexity of mangroves. However, the specific effects might be mangrove species-dependent.