How is climate change affecting our fisheries and the natural reproduction of fish?

This is a very good and important question, and a lot of scientists are asking and trying to understand that. Climate change brings many changes to the oceans. It changes temperature, food availability (in some places there is more food, in others less), how fast fish grow and how much they reproduce. All these impacts combine in complex ways, so that some fish species and some fisheries end up being winners and others might be losers. Generally, people in fisheries are used to changes and they can adapt to new conditions, especially if they work closely with scientists to regularly collect data and prepare for the future. In fact, Australian and Tasmanian fisheries are some of the few in the world who, together with the University of Tasmania, are developing climate adaptation plans. 

Regarding the natural reproduction of fish, in warmer temperatures fish often mature and start reproducing earlier and at smaller size. Together with a team of colleagues, we have tried to address the very question of how climate change and fishing together will affect fish reproduction. We found that when our simulated fisheries removed the largest fish and these populations were also affected by warming, fish reproduction declined rapidly. In contrast, when fishing selectivity was changed and caught only the medium sized fish, warming didn’t have a negative effect on fish reproduction. You can see the summary of this experiment in the picture below. This experiment suggested that to increase fish resilience to climate change and protect their reproduction we should protect the largest fish in populations.