Spatiotemporal ichthyofaunal dynamics in a permanently open estuary, Otago, New Zealand

Abstract

Understanding the spatial and temporal dynamics of the fish-assemblage structure of estuaries is indispensable in conservation and habitat-improvement efforts. This study reports seasonal as well as spatial dynamics of fish diversity of the Waikouaiti Estuary and indicates the key physicochemical variables that influence the ichthyofauna of the estuary. Fish were collected from upper, middle and lower reaches of the Waikouaiti Estuary monthly for 1 year, by using a seine net. In total, 15 species and 4967 individuals were collected during the study period. Distinct differences in ichthyofaunal composition, driven by spatiotemporal environmental heterogeneity, were observed between the three reaches of the Waikouaiti Estuary. Fish abundance was higher in the middle reach where the water is turbid. Whereas fish species with diadromous life history occurred more frequently in the upper reach of the estuary, marine-migrants and marine-stragglers were abundant in the lower reach. The present study indicated that salinity and turbidity were the best predictors of fish species composition in the different reaches of the Waikouaiti Estuary.