A new study on the oceans across the world states that global warming is likely to shrink the size of the fish by as much as a quarter in the coming decades.

The reduction in individual fish size is matched with a fall in overall fish stocks when the world's growing human population is putting greater pressure on fisheries, warn scientists.

"We were surprised as we did not think the effects would be so strong and widespread," Prof. William Cheung from the University of British Columbia told the Guardian.

His team examined the rise in ocean temperatures on growth and distribution of more than 600 species of fish and found they were expected to shrink in size by 14-24% by 2050, with biggest impact witnessed in tropical regions.

"We will see dramatic changes in the oceans reduce productivity. One billion people rely on fish for primary animal protein and it is bound to increase in developing countries. We have to get to grips with our dependence on fossil fuels otherwise we are stuffed," Roberts added.

While previous studies suggested that ocean temperatures impacted the distribution and reproductive abilities of fish, new studies state that fish sizes will shrunk heavily.

Although data project relatively small changes in temperature at the sea-bed, resulting impact on fish body size are "unexpectedly large," BBC News has reported.

When compared with actual observations of the fish sizes, model generated on future fish sizes seem to underestimate what's actually happening in the seas. Apparently, the researchers looked at two case studies involving North Atlantic cod and haddock. They found that the recorded data on these fish showed greater decrease in the body size than what the models had predicted. Other scientists stated the impact could be widely felt.

“A warmer and less-oxygenated ocean, as predicted under climate change, would make it more difficult for bigger fish to get enough oxygen, which means they will stop growing sooner,” Pauly, who worked on the study, told the Register.