Nekton communities and their seasonal variation in salt marshes of the Yangtze estuary

A first step to understand the ecological functions of nekton and promote their conservation is characterizing their community structure and dynamics. Although nekton communities in coastal wetlands (such as tidal flats, tidal creeks, and nearshore waters) have been widely reported in many regions globally, studies in vegetated salt marshes - a broadly-distributed type of coastal wetlands - has yet to be conducted in China. We investigated the community structure and seasonal variations of nekton in three salt marshes dominated by the foundational plant Scirpus mariqueter in the Yangtze estuary. We found that nekton communities in these salt marshes primarily consisted of bottom-dwelling fish and crustaceans, with a total of 11 fish species, two crab species, and one shrimp species. There were strong seasonal variations in the abundance, biomass, species diversity, and community structure of nekton, with consistent patterns across the three sites. Abundance and biomass were highest in summer (accounting for 85.42 % and 71.76 % of the total catch, respectively) and lowest in winter (both below 1 %), while species diversity was greatest in spring (11 species recorded) and lowest in winter (only one species recorded). These results suggest that nekton use salt marshes as habitats in the Yangtze estuary, depending on season. Our study provides a baseline for understanding the community characteristics and ecological functions of nekton in the salt marshes of the Yangtze estuary and highlights the importance of incorporating seasonal dynamics into such understanding.