Study: Warming Temperatures Threaten Ocean’s Biggest Fish

    27 September 2023

    A new study has warned that warming ocean temperatures could threaten some of the largest fish in the sea.

    Many scientists believe warming waters are directly linked to the effects of climate change. Research has shown that rising sea temperatures are especially dangerous for larger fish because warmer waters can harm their open-water environments.

    In one recent study, researchers estimated some larger fish species could lose up to 70 percent of their environment, or habitat, by the year 2100. These habitat losses could largely remove some of the most economically valuable fish species. The Woods Hole Oceanographic Institution in Massachusetts carried out the study.

    FILE - Andrew Lebel battles an Atlantic bluefin tuna while Capt. Pete Speeches maneuvers his boat into position about 20 miles off the coast of southern Maine on Aug. 6, 2018. (AP Photo/Robert F. Bukaty, File)
    FILE - Andrew Lebel battles an Atlantic bluefin tuna while Capt. Pete Speeches maneuvers his boat into position about 20 miles off the coast of southern Maine on Aug. 6, 2018. (AP Photo/Robert F. Bukaty, File)

    The warning comes after temperatures around the world reached record highs in July. Some scientists blame the Pacific Ocean current known as El Niño for the recent heat waves.

    El Niño is a warming of surface water temperatures in the eastern and central Pacific Ocean. The event usually causes hot, dry weather in Asia and Australia. It can also lead to heavier rain in the southern U.S. and southern parts of South America.

    Large fish – such as marlin, skipjack and others – live in areas considered among the fastest warming.

    Camrin Braun is an ocean scientist and the lead writer of the Woods Hole study. He told the Associated Press that temperatures in those environments are expected to rise as much as six degrees Celsius by the end of the century.

    Such increases would likely start a widespread displacement of the animals, Braun said. "For sure, their habitat will change. How they respond to that is an open question," he added.

    Climate scientists have been studying the heating of the world's oceans for many years. Earlier in 2023, average ocean surface temperatures climbed two-tenths of a degree Celsius in a period of just a few weeks. The jump surprised even scientists who are used to seeing continued rising temperatures.

    For large species, longer periods of warming can be harmful because of the animals' temperature needs, said Janet Duffy-Anderson. She is chief scientific officer at the Gulf of Maine Research Institute in Portland, Maine. Duffy-Anderson said large fish are often highly migratory. Increased warming could result in some species moving to northern or deeper waters in search of normal temperatures, she added.

    The Gulf of Maine lies off the northeastern US and Canada. It is warming especially quickly. This is expected to cause big population movements, especially for species of marlin and tuna.

    Large fish are important to healthy oceans because many of them, such as white sharks, are predators serving as critical pieces of the top of the food chain. Some species are also economically important to humans as food.

    The possible loss of large fish is one of the many results of warming oceans that scientists have warned about this year. One study said the collapse of ocean currents that transport heat northward across the North Atlantic could happen by mid-century. In Florida, federal ocean researchers said some ocean coral were losing their color weeks earlier than normal because of record temperatures.

    Penny Becker is with the Seattle-based environmental group Island Conservation. She told the AP the threat to large fish is another reason to raise awareness about the different ways climate change is affecting sea life. "If you're missing these components of these larger fish species, that's a missing hole in the ecosystem," Becker said.

    I'm Bryan Lynn.

    The Associated Press reported this story. Bryan Lynn adapted the report for VOA Learning English.


    Words in This Story

    species – n. a group of animals or plants that are similar and can produce young animals or plants

    predator – n. an animal that hunts and kills other animals for food

    food chain – n. a series of living things in which each group eats organisms from the group lower than itself in the series

    component – n. one of the parts of a system, process or machine