Physiological adaptations of fish

When the environment changes or when fish are moved to a new environment, the fish will gradually induce a physiological adaptation process under the new environmental conditions, such as the climate adaptation of fish to the new environment and changes in feeding habits. Among them, temperature adaptation is the most common. For fish living in temperate zones, when autumn comes and the temperature gradually turns colder, the fish gradually adapt to the drop in temperature and enhance their resistance to the cold winter; in spring, the temperature gradually rises, and as the fish Recovery, the ability to adapt to high temperatures in summer has gradually improved. Fish living in lower temperature environments have stronger ability to tolerate low temperatures but weaker ability to withstand high temperatures than fish living in higher temperature environments. For example, the death temperature of the long-snouted catfish in August in summer is 35.8°C, but in winter it is 29°C.

Fish's adaptation to temperature has a threshold, that is, it cannot exceed the temperature range in which it grows and develops. Temperature adaptation can change the initial lethal temperature of fish and also affects the tolerance time to lethal temperatures. For example, the lethal high temperature for sturgeons is 26°C water temperature, but sturgeons living under 5°C conditions are transferred to water bodies with 26°C water temperature, causing half of the individuals to die in less than 1 hour; while sturgeons living under 15°C conditions are sturgeons were transferred to a water body with the same conditions, and it took 6.5 hours for half of them to die.

Fish, like other organisms, will adapt to the new environmental characteristics after living under certain environmental conditions for a period of time, thereby ensuring the continued survival and development of the population. But this plasticity, that is, this adaptability, is actually the role of genetic genes, because different species show different adaptability, and the differences in adaptability between species are quite stable. For any species, the environment is always changing, with seasonal changes in temperature and temperature throughout the year, as well as individual fish migration to areas with very different conditions, etc. Therefore, each species can be preserved through long-term natural selection, and most of them Have certain adaptability.

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