Gastrointestinal Tracts of Fish Are Sensitive to Water Temperature Changes

Temperature changes may influence distribution of fish populations.

While fluctuations in water temperature are known to affect the distribution of fish, the precise impact on the body of individual species of fish is not particularly well understood. Research carried out at the University of Gothenburg in Sweden has now revealed that the gastrointestinal tract of fish is actually far more sensitive to changes in temperature than previously suspected, and this factor can directly impact the distribution of species.

Physiological Functions
Being ectothermic, fish are essentially dependent on the temperature of the water in order to maintain their body temperature. When the water temperature changes, this directly impacts their body temperature and the physiological functioning of the body. 

“When the temperature of the water rises, the fish’s body temperature climbs, activity in the gut increases, and more energy is needed to stay healthy,” said researcher Albin Gräns, who has studied freshwater and saltwater species in western Sweden, California and Greenland. 

Among those species studied in this research were sculpin, sturgeon and rainbow trout. The results of the study determined that some fish find it harder to absorb nutrients at higher temperatures. “Since changes in body temperature affect virtually all of a fish’s organs, it’s surprising that we know so little about how temperature changes impact their physiology,” said Gräns.

Winners and Losers
The outcomes of temperature changes will vary from species to species and are hard to predict. “If the water temperature in the Arctic rises further, some sedentary species, such as various types of sculpin, will probably struggle to maintain blood flow in the gut during the summer months, which will affect their health,” Gräns said. On the other hand, some species could benefit, notably those fish living at the bottom end of their temperature distribution range. Gräns’ research will hopefully discover which parts of the body will fail first, such as the heart and the gut.

There are ways that fish can adapt within reason, however, to temperature changes, provided that they can move freely from one area to another, although this could raise worries over increased predation. Fish can hunt and eat in one temperature and then swim to another area to digest the food, thus exploiting areas that may otherwise harm them.

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