Fish Futures Simon Stewart, Robin Holmes, Yvonne Vadeboncoeur and Sarah Bury and Sarah Crump looked at how migrating fish from the Waituna Lagoon support predators like longfin eels and brown trout in Waituna Creek, New Zealand. Using food web analysis and biomass estimates, researchers found that the lagoon’s fish, especially īnanga (whitebait), made up 60-80% of longfin eel biomass and 40-90% of brown trout biomass over two years. Predatory fish in the creek consume around two tonnes of migrating whitebait annually.

The findings suggest that connections to estuarine ecosystems are crucial for sustaining large predatory fish in degraded freshwater habitats, challenging the idea that stream restoration should always focus on headwaters. Estuaries may be more important than previously thought for supporting these fish when food is scarce.