People have depended on fish and other seafood for sustenance since the prehistoric people learned how to fish. Early civilizations are built in river banks and coastal regions because fishing is much sustainable the hunting. However, as society progress, the more than fishes and other marine animals become at risk. Thanks to climate change.
This reality was revealed by the extensive analysis of recent trends in marine biodiversity. The increasing temperatures in seas have reduced the productivity of some fisheries by 15% to 35% over the last eight decades, although there are fish species that are thriving in warm waters.
According to the study, the net effect is that the world’s oceans cannot produce as much sustainable seafood as before. It also warns that the situation is likely to worsen as the problem is quickly accelerating in the oceans.
However, the study also suggests that well-managed fisheries are thriving and have become more resilient to the rising water temperature, says Rainer Froese, a marine ecologist with the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, who was not involved in the work. “We have to stop overfishing to let the gene pool survive, so that [the fish] can adapt to climate change,” he says. “We have to give them a break.”
As cold-blooded animals, fish mirror the temperature of the water they swim in. When the water gets too warm, the enzymes they use for digestion and other functions are less efficient, impairing growth and reproduction. Also, warm water contains less oxygen, a further stressor.
Despite these well-known problems, only a few scientists have looked into the impact of climate change on the world’s oceans in terms of fishery production.
Chris Free, a fisheries scientist, dove into the topic for his dissertation at Rutgers University in New Brunswick, New Jersey. He created a computer model of the way fish populations respond to temperature, relying on a large database of scientific assessments of stocks that represent roughly a third of the fish caught around the world. Free, now a postdoc at the University of California, Santa Barbara, looked for patterns of how these stocks had responded to changes in sea surface temperature.
“Managing a stock of fish, in simple terms, is like withdrawing cash from a bank account that earns interest. Each year, a certain amount can be caught by fishing boats without depleting the stock—that portion is known as the maximum sustainable yield. A more productive fishery—where the water temperature is optimal and food plentiful, for example—is like a bank account with a higher interest rate, which means more fish can be sustainably caught.” said Erik Stokstad in an article published in ScienceMag.
The study of Free and his colleagues revealed that: “Out of 235 stocks, Free and his colleagues found a few winners. Nine stocks had become on average 4% more productive. These stocks are in places where rising temperatures have made too-cold water more suitable for fish, such as far north and south of the equator. Off the coast of Newfoundland and Labrador in Canada, for example, the maximum sustainable yield has increased by 14% since 1930. And fishing there could get even better. According to the new research, the productivity of Greenland halibut will increase 51% with each degree Celsius of warming. That’s like getting a big, fat boost to the interest rate on your saving account.”
“This local good news is outweighed by 19 stocks elsewhere that are on average 8% less productive than before. Many of these are around northern Europe and Japan, and they will likely continue to decline as their environment continues to heat up. Boats chasing Atlantic cod in the Irish Sea face a particularly grim future: The maximum sustainable yield of this stock will shrink by 54% for each additional degree of warming, the team reports today in Science.”
According to Free, the overall decline will most likely to steepen. Since 1930, average sea surface temperatures have risen by about 0.5°C. By the end of this century, more than three times that amount of warming will likely happen, and marine heat waves will become more frequent. Although temperatures will become more favorable to fish in higher latitude waters, “those benefits can’t last forever,” Free says. “There probably is a tipping point.”
Fishes, however, are not the only animals that are being threatened by climate change. Scientists have also said that because of a killer fungi, frogs are starting to become extinct. The rapid increase in rainforest temperature even more empowered the killer fungi. Insects are also in fast decline due to climate change. This serves as a scary reminder of the future we reap if we continue our path to unsustainable tomorrow.