Abstract
This thesis investigates the spatial and temporal dynamics of fish and invertebrate populations within coastal wetlands in Southland, New Zealand. Each chapter focusses on a different aspect of the community and its interaction with the environment. Initially fish in four systems were surveyed over two years, where great variation in abundance and diversity of species was observed, particularly in relation to connectivity to other waterways (Chapter 2). During the survey period, significant dewatering events occurred; the duration of these low water events had a significant impact on how rapidly the community recovered. Following this was an in-depth investigation of the invertebrate community dynamics over a spring to autumn sampling period, focussed in one of the initial wetland areas, a constructed wetland system with many small interconnected ponds (Chapter 3). A progression of dominant microcrustaceans were observed as was a succession of larger more predatory taxa. Spatial variation was also observed, related to hydrological connectivity and nutrient levels. An investigation into īnanga population dynamics was also conducted, as they are a key species in this system and there is a notable gap in knowledge on their habits within small ponds (Chapter 4). This found spring-hatching fish with a faster growth rate than those that hatch later in the year. Diet preferences indicate both benthic and pelagic foraging, and the presence and consumption of microplastic filaments. The study culminates in an in-depth investigation of the recovery of both fish and invertebrate communities after a drought within one system, tying together observations from the other chapters (Chapter 5). This highlighted the importance of spatial heterogeneity and connectivity for rapid invertebrate recovery, as well as the value of deep channels that are more resistant to drying in supporting fish recolonization. Overall, this research has provided insights into communities of fish and invertebrates, generating new information relevant to the specific systems and species as well as the wider body of knowledge on wetlands.