Global Warming Contributes to Smaller Fish Size

According to new research, the fish population is likely to significantly decrease in size by 2050 due to global warming and changing oxygen levels in the oceans. The average weight of over 600 types of marine fish including cod, halibut and flounder is expected to decrease by about 14-24 percent by from 2000 to 2050.

Rising water temperatures caused by global warming have the effect of cutting off the amount of oxygen in the oceans. This may also lead to dwindling catches for fisheries. According to William Cheung of the University of British Columbia in Canada, “The reductions in body size will affect whole ecosystems.”

Cheung is a lead author of the findings, posted in the journal Nature Climate Change. Cheung and his team believe that smaller fish sizes will have major effects upon ocean food webs and fisheries and the human consumption of fish. As human burn fossil fuels, life becomes more difficult for oceanic fish because warm water is not capable of holding as much dissolved oxygen as colder water. Oxygen is vital for these fish for respiration as well as growth.

“As the fish grow bigger and bigger it will be difficult to get enough oxygen for growth. There is more demand for oxygen as the body grows. At some point the fish will stop growing,” Cheung deduced from the study, based upon computer models.

Fish are also more likely to migrate from tropic seas towards cooler waters North and South. As water gets warmer it gets lighter as well, mixing with oxygen near the surface of the water rather than the cooler deeper levels where many fish live.

In the Indian Ocean fish size is expected to shrink the most, by an average of 24 percent, followed by a 20% decrease in the Atlantic and a 14% decrease in the Pacific. The study also predicted that most fish populations would towards the North and South poles at a median rate of 17.1 to 22.6 miles per decade from 2000 to 2050.

Marine food chains are expected to suffer from these changes most of all. In addition to over-fishing and pollution, many fish like cod swallow their prey whole, and can only eat fish that can fit in their mouths. Cod may now become less fearsome to many smaller fish, and allow these smaller species to suddenly thrive.

Increasing climate change should be the cause of all of this; the study predicts an increase in world temperature of between 3.6 to 9.7 degrees Fahrenheit by 2100.

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