Migration in fishes - Overwintering Migration

Fish Overwintering: Overwintering is a process that's attended by fish including some other animals to maintain or survive normal activities during winter or dry periods when the food supply is decreased.
In particular, the word 'Winter' does not only mean extreme cold, it also indicates dry season or dry conditions. Fish food infusion decreases in winter and many fishes have a reduced metabolic rate to reduce energy expenditure. To protect themselves from the lack of food, fish move to safe places to escape extreme cold or winter lazily, the process of spending winter or dry season is called Overwintering migration.

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Reasons for Overwintering migration:

• Fish migrate when the water temperature drops below the compassion level of fish.

• Eating habits are observed, and as a result, such migration happens.

• Fish migration happens due to reduced food intake.

• Overwinter migration to protect themselves from the extreme cold of winter and the drying of water bodies.

• Due to the decrease in metabolism and activity of fish, they dive into this type of migration.

• Due to the reduction of dissolved oxygen in the water, fish migrates.

• Overwintering migration of fish occurs primarily to ensure the survival of the species.

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Mechanism of Overwintering migration: Overwintering of fish migration occurs through a combination of two processes. One is hibernation, the other is migration. Each fish survives in a specific tolerable temperature of the water body. Water temperature affects several physiological activities of fish. This also affects food intake. When the temperature of the water body drops too much, hibernation means the fish overcome unfavourable life cycle conditions. During severe winters, fish move from grazing grounds to relatively warm wintering grounds located in rivers or oceans. They slow down the metabolic rate and draw energy from the body's stored fat.

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Overwintering migration of few fishes:
Atlantic Sturgeon, Atlantic salmon migrate to spend the winter. Antarctic cod fish hibernate in winter. In European lakes, Rutilus rutilus migrates to nearby rivers in winter only to avoid predation. Various Carp fishes settle in the mud at the bottom of the lake to spend the winter. At the end of the foraging migration, flatfish migrate to the deeper parts of the ocean to spend the winter in favourable conditions.

^{Reference- Book of Fish taxonomy, fish physiology and ichthyology | Reference- Wikipedia}