Posted in | News | Global Warming | Ecology

Climate Change is Driving Perch to Outcompete Cold-Water Fish in Arctic Lakes

Scientists analyzed the condition of ecosystems of high latitude lakes and found out that increasing of water temperature leads to increasing of population, rapid growth and early maturation of perches. It points to the fact that in future thermophilic fish like perch can force out cold-water salmon species. Authors came to the conclusion that if you want to conserve biodiversity of lakes, it is necessary to reduce catching of fish living in cold water. Results of the research are published in Ecology and Evolution journal.

Climate change leads to the fact that people and many animals ashore suffer from droughts, more rapid spread of infectious diseases. In ocean temperature raising leads to ice melting, water conversion and death of several species as a consequence. Besides this the inhabitants of fresh reservoirs in high latitudes also suffer. Exactly in this region there is the most rapid increasing of average annual water temperature. According to forecasts it will grow minimum till 2100. Due to the fact that fish are cold-blooded animals, that means they can't keep constant body temperature, the warming of the environment plays the vital role in their lives. Each species of fish has its own temperature niche – the diapason of temperatures in which they feel well. For example, temperature optimum for salmon is about 18-26 °C, and for fish from perch family – approximately 16-27 °C. Some crucial life stages have narrower temperature frames for survival and successful development, so, for example, spawn develops within 7-18 °C. Moreover, temperature restricts such biological processes as food consumption and growth. If there is enough food, maximal speed of growth is reached at temperature optimal for animal. By this if animal lives at temperatures that are lower than optimal, the speed of their growth can increase with climate warming. High speed of growth leads to large sizes and as a consequence to early maturation. Both these factors raise survival rate of individuals and help to increase their population.

In order to understand how climate influences the composition of fish communities in polar regions, scientists from UiT The Arctic University of Norway, University of Helsinki and Institute of North Industrial Ecology Problems (Apatity) analyzed eleven fresh water lakes situated beyond the Arctic Circle. Time of the observation of reservoirs under examination from which authors analyzed fish varied from 8 to 32 years. Total amount of caught fish from 11 lakes was almost 60000, 12000 of them were perches. Researchers counted a percent of perch in fish community. They found out that their quantity in tested lakes increased from 10% to 70 % in the last 30 years. It should be noted that this marker differs from lake to lake significantly, because it is influenced by many factors, for example, amount of available food or predators. However general tendency shows displacement of cold-water fish. Also, scientists came to conclusion that annual growth of perch populations and percent of year-old individuals in them also increase in the course of warming.

Besides this, in two lakes with great populations of perch authors estimated the speed of growth of fish by measuring the annual growth, likewise you do it with annual rings of trees. The research showed that warming speeded the growth of young individuals, and, as a consequence, led to faster maturity. The age was lower for about 0,8 years on every centimeter of growth of length of young individuals, from 1 to 4 years old.

"Our research has shown that perch in the course of warming gradually displace cold-water fish species. That points to the fact that it is necessary to control current changes in order to elaborate strategies of adaptation to climate changes and conservation of cold-water fish species in Arctics", – tells Petr Michailovich Terentiev, Cand.Sc.Biology, senior research scientist of Institute of North Industrial Ecology Problems.

The material was prepared with the financial support of the Russian Ministry of Education and Science within the framework of the federal project "Popularization of science and technology".

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