Ichthyofaunal assemblages in shallow littoral habitats of permanently open estuaries and intermittently closed and open lakes or lagoons in Otago, New Zealand

Abstract

Fish assemblages of New Zealand estuaries are poorly studied, and knowledge of the effects of estuary-ocean connections on the ichthyofaunal composition of estuaries remains limited. Understanding the status of fish composition of estuaries is crucial for planning for sustainable management of aquatic ecosystems. In the present study we sampled fish using a seine net from lower reaches of six permanently open estuaries and six intermittently closed and open lakes or lagoons (ICOLLs) along the Otago coastline during winter 2016 and summer 2017. Marked differences in ichthyofaunal composition were observed in the shallow littoral habitats of permanently open estuaries and ICOLLs. Fish assemblages reflected estuary-ocean connection status of estuaries during both seasons. ICOLLs showed greater fish abundance than permanently open systems. Fish abundance was higher in summer than in winter in both estuary types. Fish species with marine-estuarine opportunist and estuarine-migrant life histories dominated permanently open estuaries. Conversely, species with a diadromous life history but known to form landlocked populations were abundant in ICOLLs. Salinity and temperature were correlated with fish abundance in both estuary types.