Lake food webs will undergo change, or be ‘re-wired’, as the impacts of climate change intensify. Understand how differing fish community assemblages will respond to projected climate change impacts – prolonged stratification and increased eutrophication – is important for guiding fish conservation efforts.
The native freshwater fish kōaro/climbing galaxias (Galaxias brevipinnis) were once abundant in New Zealand’s central North Island lakes. Following the introduction of rainbow trout (Oncorhynchus mykiss) and subsequently common smelt (Retropinna retropinna) as a forage fish for trout, kōaro numbers have declined. This study aims to understand the trophic interactions between these fishes in lakes and how they are likely to be effected by projected climate change impacts; namely prolonged stratification and eutrophication.
In this presentation we will discuss how we have worked with local indigenous lake owners/managers to develop a fish sampling program which local traditional knowledge and techniques, while also incorporating biophysical science, to inform conservation aspirations. One key aspect is maximizing the information generated from all individual sacrificed fish. This includes individual-level quantification of growth (otolith daily growth rings), diet (using both δ15N & δ13C stable isotope analysis and gut DNA analysis). The highly individulalised assessments of fish provide greater statistical power for small datasets. We will discuss insights from these data including: context-specific growth responses to diet variation; and, integration of the data with agent-based lake food web models.