The global warming of oceans will make some fish balloon bigger in size, new research has found.
Scientists probing the effects of climate change have now discovered that for every one degree change, sizes could fluctuate by up to 40%.
While most species will get smaller, 45% will get bigger.
This new finding puts a line through previous studies that claimed all fish would get smaller.
Experts are now warning that this poses a threat to the normal pattern of marine life and conservation efforts.
Nicholas Payne, assistant professor in zoology in Trinity College Dublin, co-authored this ground-breaking report.
The scientist from the university’s School of Natural Sciences said today: “One of the reasons this study is important is that it shows the complexity of species’ responses to warming in our oceans.
“Much of our understanding of the temperature-size relationship comes from the laboratory.
“Taking our predictions to the wild shows us there is a lot we still need to learn about this hugely important phenomenon.”
A team of scientists used 10 million visual survey records of 335 fish species across coastal locations in Australia, which spanned decades.
The scientists confirmed that changes in water temperature drove changes in fish size.
This study also included data collected through the decades-long Australian Temperate Reef Collaboration monitoring program and the citizen science Reef Life Survey program.
Before now experts claimed fish sizes would reduce as temperature increased.
But it turns out that while temperature has a significant impact, it causes different fish species to react differently.
Some reduced in size as predicted, 55%, but others, 45%, increased in size.
In general larger species tended to get even bigger in warmer waters, while smaller species tended to get smaller.
Fish size changed between 4% and 40% per one degree change in temperature.
Ocean temperatures are set to rise between 1.2 and 3.2 degrees by 2100.
This suggests the impact on fish size will be very significant.
It will have serious implications for fisheries.
The crucial message is that warming seas will have unanticipated impacts on the entire ocean food chain, which could threaten marine conservation initiatives.
Dr Asta Audzijonyte, lead author of the study, from the University of Tasmania, insists that she was surprised by the results.
She said: “Initially, we were not sure that we would see strong temperature effects, because data from wild fish populations are often very noisy.
“But our careful analyses revealed the unexpected result that fish species respond to temperature change in quite different ways.
“Our results are important because they could help us forecast how different species will respond to future warming of the oceans.”
