Scientists make alarming discovery after analyzing stomachs of marine predators over 3 decades

Meal sizes for fish living in Great Britain's seas are shrinking due to overfishing and warmer waters, according to a study from the University of Essex. 

What's happening?

Scientists analyzed government data that documented what was in the stomachs of more than 50,000 marine predators. The samples were collected over 35 years in the North Sea, English Channel, and Norwegian Sea. 

The team found that over time, fish in warmer waters were feeding on smaller and smaller prey. The reason is that higher water temperatures offer less oxygen and speed up metabolisms, so animals don't grow as large, a University of Essex report on the study noted. 

The trend was exaggerated wherever commercial fishing operations were removing more of the ocean's available food, according to the full findings published in Nature. 

Why do fish meal sizes matter?

The amount of food swimming in the sea directly affects how much energy predator species can produce and store. For these meat-eating fish, less available energy means less strength and resilience, which can make it harder to survive. 

That might sound like a win for the small fish of the world, but it's not. The ocean needs fish that eat other fish, just like any other ecosystem maintains order through the food chain. 

Disrupting that underwater balance can make it harder for humans to catch, sell, and eat seafood, let alone for the animals to live their lives. 

What can be done to protect the ocean's fish?

Mixing up what types of seafood you eat can help ease the burden on the ocean. Shopping smarter at the grocery store can help too. 

The authors of the study stressed that their results apply to ecosystem management strategies and fishing operations. 

They recommended that policies not tackle species one at a time and instead address the food web as a whole, alongside the dual threats of rising temperatures and overfishing.

"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," lead researcher Amy Shurety said, per the University of Essex report.

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