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Do fish suffer from oxygen starvation?

Do fish suffer from lack of oxygen?

Based on their insights, the researchers identified – in great detail and worldwide – which fish are likely to thrive in which waters, from oceans to small rivers. “We calculated this for two ‘hypothetical’ fish, one large and one small. Small fish do well in warm environments, such as the tropics, and large fish do better in colder regions. We may be able to extend these projections in the future to calculate the effects of environmental change.” Credit: Radboud University

Larger fish are more likely to suffer from lack of oxygen in warm water than smaller species. The same applies to fish with large cells, researchers from Radboud University concluded in their latest study. In addition, marine fish are less tolerant of oxygen-poor water than freshwater fish. Based on these insights, the researchers ultimately want to predict which aquatic species are at risk from changes in their habitat due to global warming and human activities. The study will be published in the journal Global Change Biology on July 25.

Falling levels of dissolved oxygen are a major problem for fish and other aquatic organisms. The oxygen content decreases because the water is warming due to climate change and because it is becoming increasingly polluted. General biological rules can tell us which fish characteristics are beneficial or harmful when environmental conditions change. “Once we identify these rules for fish,” said researcher Wilco Verberk, “we can ultimately predict which fish species are most at risk from environmental changes.”

Large and small cells

There is a lively debate among biologists about the role of oxygen in fish sensitivity to water subject to warming. “Many oxygen hypotheses are hotly debated. The problem is that the different effects are lumped together. For example, some studies look at how fish respond to oxygen levels in the water, but don’t consider water temperature or fish size. As a result, the reported patterns are variable,” explains Verberk.

Verberk and colleagues systematically separated the different effects and collected data on oxygen deficiency tolerance from 195 fish to resolve this discussion. When analyzing the data, they saw that larger fish are more sensitive to oxygen stress, but only in warm water. When the water is cold, the effect is reversed.

The researchers saw a similar effect in fish with relatively large cells. “Many people think that all animal species have the same cell size, but some animals have large cells and some have small cells, even within the same species. There are many advantages to having small cells, especially in warm water. Small cells have relatively more membrane surface , which is needed to absorb oxygen from their environment.”

Fresh water and salt water

In addition, the researchers found differences between freshwater fish and marine fish. “Far too often, scientific studies only compare marine and terrestrial life. Freshwater species are sometimes lumped together with terrestrial species. It is a missed opportunity because taking these differences into account can greatly enhance our understanding of the environmental impacts of climate change. increase.”

According to the study by Verberk and colleagues, freshwater fish appear to be more tolerant of oxygen-poor water than marine fish. “The explanation probably lies in different selection pressures on freshwater fish during their evolutionary history. In the ocean the temperature is relatively stable, but in fresh water the fish have to deal with higher temperatures more often. especially in lakes, for example due to the presence of algae.”

New model predicts that larger fish will suffer from respiratory distress more quickly

More information:
Body mass and cell size determine fish tolerance to low oxygen in a temperature dependent manner, Global Change Biology (2022). DOI: 10.1111/GCB.16319

Provided by Radboud University Nijmegen

Quote: Do fish suffer from lack of oxygen? (2022, July 25) retrieved on July 25, 2022 from https://phys.org/news/2022-07-fish-oxygen-starvation.html

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