Nature Affected by Climate Change - Update

According to a new study, fish are the latest species to shrink in size as a result of climate change.  The fish in question now weigh approximately half as much as they used to, head report author Martin Daufresne, from the French-based Cemegraf Public Agricultural and Environmental Research Institute, wrote.  He added: ”Size is a fundamental characteristic that is linked to a number of biological functions, such as fecundity – the capacity to reproduce.”

Overall, smaller fish do not usually produce the quantity of eggs associated with larger fish.  They are also a less nourishing meal for larger, predatory fish and humans and – adding in the climate change phenomenon – these facts combined could significantly affect the food chain and/or marine ecosystems.

Shrinking Fish

The new shrinking fish study comes hot on the heels of a similar report concerning Scottish sheep, which Enviro-News covered in a previous News Item.  Aware of this report, Mr Daufresne highlighted how climate change might well be having a “significant impact on organisms in general.”

Daufresne assessed fish living in a number of areas, including the North Sea, the Baltic Sea and multiple streams and rivers.  He and his co-workers found that – over the past three decades – many had reduced in weight by as much as 50 per cent.  This shrinking, he explained, ”...was an effect that we observed in a number of organisms and in a number of very different environments – on fish, on plankton, on bacteria, in fresh water, in salt water - and we observed a global shrinking of size for all the organisms in all the environments.”

Daufresne acknowledged that human activities like fishing had also impacted on fish size, but said these could not be the only factors. 

”Although not negating the role of other factors, our study provides strong evidence that temperature actually plays a major role in driving changes in the size structure of populations and communities”, he wrote.

Climate Change and Fish

Previous studies on climate change and fish showed how fish breeding trends, along with the extent to which they travelled, had already changed as the water warmed up.  They also confirmed the concentration of smaller fish in warmer waters was becoming denser.

The new shrinking fish/climate change study features in the current edition of the Proceedings of the National Academy of Sciences publication.