Relationship between Rainfall and Fish Production

QUESTION

There’s an old saying of “a dry year on the land is a dry year in the ocean”. In light of this, what is the relationship between annual rainfall and commercial fish catch, and how might this be impacted as the climate changes?

ANSWER 1

By: Dr Stephanie Brodie

Yes that’s right, rainfall can be a good proxy of river flow to the oceans, which brings nutrients to coastal waters. These nutrients help fuel the base of the food web and increase ecosystem productivity – leading to increased catch in fisheries. Some fished species will also depend on this connectivity for their reproduction, where species will migrate between salt and fresh water to complete their life cycle.

This connection between rainfall and fisheries productivity is particularly notable across northern Australia, which has a monsoonal climate. Much of the biota in these ecosystems have life histories that take advantage of large seasonal river flows.

These dynamics between future rainfall and fisheries catch are explored in Australia’s National Climate Risk Assessment. The figure attached shows the change in annual rainfall across Australia for the near future, mid-future, and far-future. The minimum, median and maximum represent differences among models, with differences indicating how uncertain the models are. The key take-away here is that change in annual rainfall under climate change is uncertain, except for parts of southwest Western Australia and areas in southeastern Australia that show consistent drying across all models. Planning for both wetter and drier futures will likely be required for management.

Things to note: (1) large percentage changes in the arid interior are relative to low total rainfall values where small changes to rainfall can lead to a large percentage change; (2) Total annual rainfall does not fully capture other important rainfall dynamics, such as the timing or size of rainfall events.