Climate Change strikes again: Warming rivers are reducing fish recruitment

By Dr Mischa Turschwell

Read Time: Words 235 about 2 mins.

Australia’s freshwater fishes are iconic, but they’re in serious danger, as freshwater ecosystems become increasingly threatened by altered land-use and climate warming.

Northern River Blackfish. Photo: The Adelaide Advertiser .

Successful breeding and survival of juveniles (recruitment) is necessary to maintain healthy functioning populations and is important for species conservation.

There is an urgent need to understand what factors contribute to successful breeding and juvenile survival for Australia’s freshwater fishes, especially as many freshwater fish species are affected by events like those that led to the recent fish kills in the Murray-Darling Basin.

In recent research, we explored how different environmental variables affect juvenile fish recruitment in the threatened northern river blackfish in the Northern Murray-Darling Basin, QLD.

There is an urgent need to understand what factors contribute to successful breeding and juvenile survival for Australia’s freshwater fishes, especially as many freshwater fish species are affected by events like those that led to the recent fish kills in the Murray-Darling Basin.

We found the highest numbers of juveniles in the coldest stream segments, and strong evidence to suggest that stream temperature was the primary variable that determined recruitment success.

We also found that temperature interacted with the amount of tree and shrub coverage that was present on the stream bank (i.e. riparian vegetation). We found more juvenile blackfish in cooler streams that also had more vegetation and cover compared to cooler streams without vegetation.

We suggest management needs to primarily target restoration across the catchment to cool and restore stream temperatures that are suitable for river blackfish.

Murray Darling Basin. Photo: Mickw78.

Locally restoring riparian vegetation will undoubtedly contribute to reducing stream temperature, but may not improve blackfish recruitment unless warming streams are addressed at catchment scales.

This work appeared in Marine and Freshwater Research

You can follow Dr Mischa Turschwell on Twitter: @turschwell

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