Climate Change Triggers a Decrease in Number of Fish Species

Specialists indicate that global warming may cause a decrease in fish species, significantly affecting their number. The poor quality of oxygen levels and the warming temperatures of the sea will determine a shrink in the number of fish species. The new study indicates that all sort of species will be affected, from groupers and tunas to cod, haddock, thresher sharks and salmon.

The warm water of the seas tend to speed up their metabolisms, and creatures like squid and fish will need to draw more oxygen from the ocean. One of the factors that determine warm temperatures in the water is thermal pollution. Thermal pollution appears when several plants and factories use water from a natural body water to cool their machinery and then discharge it back with a higher temperature.

Pauly’s and Cheung’s study

Warming seas reduce the availability of oxygen in several areas of the oceans. The new study developed by scientists at the University of British Columbia indicates that the bodies of fish tend to develop faster than their gills. Therefore, these creatures will end up needing a lot more oxygen to sustain their normal growth.

William Cheung claims that the body size of fish usually decreases by 20% for every 1 degree Celsius rise in the temperature of the water. William Cheung is the author of the new study and the director of science for the university’s Nippon Foundation – Nereus Program.

Specialists argue that these dramatic changes may have a significant impact on different marine food webs, disrupting many predator-prey relationships. Daniel Pauly indicates that their lab experiments show that the largest fish will be the first that will be affected. Pauly is a professor at the university’s Institute for the Ocean and Fisheries, principal investigator for the Sea Around Us and also the lead author of the study.

From the point of view concerning the respiration process, small species of fish will have an advantage. Even if many scientists praise this discovery, not all of them believe that the work developed by Cheung and Pauly completely supports the dramatic discovery. However, the new study was recently released in the journal Global Change Biology, serving as a proof for all the incredible findings.

Fish gills may not develop as fast as the rest of their bodies

Cheung, Pauly and other authors developed a study back in 2013 when they concluded that the average body weight of 600 species of ocean fish is likely to shrink up to 24% by 2050. Of course, the main cause of this terrible change would be global warming.

Even if common people could not imagine such a thing, when it comes to fish, this is a huge problem. To understand the issue, it would be like people trying to breathe through thin straws.

Other experts developed a connection between smaller fish sizes and oxygen. For instance, in the North Sea, sole, herring, whiting and haddock registered a significant decrease in size where the oxygen levels were poor. Despite all this, Cheng’s and Pauly’s study was considered by others to be overly simplistic.

Furthermore, this year, a group of European physiologists indicates that Pauly’s main premise regarding the size of fish’ gills was completely wrong. Therefore, Cheung and Pauly decided to implement the use of more sophisticated models to re-examine the theory.

Haddock fish swimming in the sea

The gills of some fish species may not develop as fast as the rest of their bodies.

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The refined study

Now, the new study abandons the old theory, explaining in more details the gill theory. Furthermore, they argue that their new study can serve as a guiding principle for future studies. The new study suggests that the original conclusions were exaggerated, underestimating the scale of the issue fish will soon experience.

For instance, the study from 2013, indicated that climate change might affect less the size of some fish species, like tuna. The refined research claims that fast-swimming tunas are likely to be more susceptible compared to other species.

Cheung claims that in some parts of the tropical Atlantic there are regions where the levels of oxygen are low. Previous studies have indicated that tunas may adapt and alter their range to avoid the unfavorable water. Therefore, the distribution of tunas is closely related to the areas with decreased levels of oxygen.

Critics and specialists’ opinion

Nick Dulvy believes that Pauly’s and Cheung’s new theory is far more convincing than their previous work. Nick Dulvy is a marine biologist at Simon Fraser University. He indicates that he has his own research that somehow confirms the ideas presented by Cheung and Pauly. When fish grow bigger and heavier, they will reach a point when the oxygen intake will not be enough.

Jeppe Kolding is a biology professor at the University of Bergen in Norway. He believes that Pauly’s concept helped him elucidate the shrinking of Nile tilapia, guppies and a sardine species from Zambia. Pauly’s theory explains the phenomenon that Kolding encountered in Africa.

Hans-Otto Poertner claims that Pauly’s theory does not account for how some species manage to adapt to ocean’s changing temperatures. However, he argues that the two scientists use convincing arguments in their theory.

Sjannie Lefevre continues to say that Pauly’s theory is not so convincing. Lefevre is a physiologist with the University of Oslo in Norway and a lead author of the critique published this year. She indicates that she is not at all impressed by Cheung’s and Pauly’s attempt to contradict critics’ arguments.

Lefevre indicates that fish are capable of adapting to the environment they live in, developing larger gills. She says that nothing could stop gills to develop as fast as the rest of the body.

Summing up

This incredible study which supports the idea of a decrease in fish species developed a lot of controversies. The new study indicates that scientists need to be careful when using such a principle to refer to multiple species. However, this principle offers some insight which is otherwise difficult to reach. Global warming and thermal pollution can determine a severe increase in water temperatures. Therefore, fish species will be in danger. That is why authorities need to work harder to annihilate climate change effects.

Image Source: Lastminute

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William E. Eubanks

I'm one of the main writers on the site; mostly dealing with environmental news and ways to live green. My goal is to educate others about this great planet, and the ways we can help to protect it.

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