Factors Affecting Induced Breeding in Fishes

Environmental factors like temperature, water condition, light, meteorological conditions etc are important factors controlling the reproduction of fish.

Temperature:

• There is an optimal temperature range for induced breeding of culturable fishes.
• Critical temperature limits exist, above and below which fish will not reproduce.
• Warm temperature plays a primary role in stimulating the maturation of gonads in many fishes. Temperature has a direct effect on gonads, regulating their ability to respond to pituitary stimulation and effects on primary synthesis and release of gonadotropins.
• Major carps breed within a range of temperature varying from 24-31°C.

Light

• Light is another important factor controlling the reproduction in fishes.
• Enhanced photoperiodic regimes result in early maturation and spawning of fishes like Fundulus, Oryzias, etc.
• Cirrhinus reba attains early maturation when subjected to artificial day lengths longer than natural day even at low temperature.

Water Currents and Rain

• Rheotactic response to water current is well established in fishes.
• Fresh rain water and flooded condition are the primary factors in triggering the spawning of carps.
• The sudden drop in the level of the electrolytes in the environment caused by the heavy monsoon rains induces hydration in the fish and stimulates the gonads resulting in its natural spawning.
• Successful spawning of fishes has been induced on cloudy and rainy days, especially after heavy showers.

Hormonal Influence

• Gonadotropins have been found to increase during spawning and decrease afterwards.
• Due to the presence of females, there is an increase in gonadotropin level in males.
• FSH and LH have been reported to influence gonadal maturity in carps.