Fish are shrinking because of climate change.
Climate change is causing fish to shrink
Researchers have found that warmer water means plankton - the microscopic organisms that fish feed on - are reduced in size which deprives the sea creatures of nutrition from their meals.
University of Tokyo experts analysed the individual weight and overall biomass of 13 different species of fish - including mackerel and sardines - between 1978 and 2018 as well as seawater temperature data from 1982 to 2014.
Analysis revealed that global warming has led to more competition for food and contributed to the shrinking.
Researcher Professor Shin-ichi Ito said: "With higher temperatures, the ocean's upper layer becomes more stratified, and previous research has shown that larger plankton are replaced with smaller plankton and less nutritious gelatinous species, such as jellyfish.
"Climate change can alter the timing and length of the phytoplankton blooms, explosive growth of microscopic algae at the ocean's surface, which may no longer align with key periods of the fish life cycle."