Fish face smaller meals due to warmer seas and fishing
University of Essex
Fish across Britain’s seas face ever-smaller meals as warmer seas and commercial fishing squeeze ocean food webs, new research suggests.
Research by the University of Essex and the UK Government’s Centre for Environment, Fisheries, and Aquaculture Science (Cefas) found strain across warm and highly fished areas of the Northeast Atlantic leaving predators such as cod, haddock and thorny skate, with less energy from every meal.
The researchers examined data from the stomach contents of more than 50,000 marine predators collected over 35 years from waters including the North Sea, English Channel and Norwegian Sea.
They found that in warmer waters, predators were feeding on smaller fish and invertebrates such as sprat, krill and crabs.
That matters because smaller meals deliver less energy, potentially weakening predators and making marine ecosystems more fragile.
The problem is intensified in areas of high commercial fishing, where larger species are typically more heavily depleted.
This reduces the average size of prey available, compounding the effects of climate change such as increases in sea surface temperatures.
Lead researcher Amy Shurety from the School of Life Sciences said the study shows that the impacts of climate change and commercial fishing need to be looked at together to protect ocean ecosystems.
She said: “Sustainable fishing and eating a more diverse range of seafood at home, can help protect marine ecosystems as the climate changes.”
The study, published in Nature, shows prey species are shrinking not because large species are disappearing, but because individual animals within the same species are getting smaller.
This is because warmer water speeds up metabolism, holds less oxygen and favours smaller bodies that are easier to sustain.
As prey shrink, predators respond by targeting a wider range of species and seeking out the largest prey still available.
Each 1°C rise in temperature leads to about a 1.8% decrease in the size of prey predators eat.
But feeding on more prey lower down the food chain can make energy transfer less efficient, leaving top predators potentially with less fuel to survive and reproduce.
The researchers warn this could undermine the long-term resilience of marine ecosystems unless fisheries policy shifts towards managing entire food webs, rather than individual species in isolation.
Ms Shurety added: “Marine ecosystems are often hit by multiple pressures at the same time and looking at these pressures one by one can hide what’s really happening.
“Our findings show that in oceans that are both warmer and heavily fished, predators must eat more smaller prey to survive.
“This combined effect would be missed if dynamics of climate change and commercial fishing were considered separately.
“Which suggests that to protect marine food webs, it’s essential that climate change and fisheries are managed together, not in isolation.”
The researchers used the diet data collated by Cefas.
Journal
Nature Communications
Method of Research
Data/statistical analysis
Subject of Research
Animals
Article Title
Commercial fishing amplifies impacts of increasing temperature on predator-prey interactions in marine ecosystems
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