Mechanism of hilsa (tenualosa ilisha) migration and its impact to nature

Mechanism of Hilsa (Tenualosa ilisha) Migration and its Impact to Nature
Tenualosa ilisha (ilish, hilsa, hilsa herring or hilsa shad) is a species of fish in the herring family (Clupeidae), and a popular food fish in South Asia. Five type of ilish can be found worldwide. Yearly ilish caught are 5,000,000 ton. Among them, 50%-60% are caught by Bangladesh, 15%-20% are caught by India, Pakistan and rest 5%-10% are caught by Malaysia, Thailand, China, Vietnam and Sri Lanka. The fish contributes about 12% of the total fish production and about 1% of GDP in Bangladesh.

1. Mechanism of Hilsa ( Tenualosa ilisha ) Migration and its Impact to Nature

2. Tenualosa ilisha Family: Clupeidae Estuarine or a Marine Fish Contributes 1 % of GDP in Bangladesh It is also the national fish of Bangladesh.

3. Common Names

4. Description and habitat

5. Food value

6. Migration And Behavior Main causes of migration are spawning and search of food. The mature fish migrate to the upstream and rivers from the sea during their spawning season for having less salinity in this environment. Males ascend to the spawning ground earlier than the females after spawning the hilsa return to the sea. The newly hatched larvae gradually become juvenile. And this jatka started to migrate to the sea later on.

7. Migration Circuit Most fishes have three points in their migratory circuit A. The Feeding Ground B. The Spawning Ground C. The Nursery Ground

8. Diagrammatic Route of Migration Circuit Adult Stock Feeding Ground Spawning Ground Juvenile Nursery Ground Denatant Denatant Denatant Contranatant

9. Many factors influence migratory movements. They may be physical, chemical and biological. Physical factors: Bottom materials, water depth, current and tide, turbidity , temperature , and light intensity. Chemical factors: Salinity , alkalinity, dissolved gases, odor, tastes, and pollutants. Biological factors: Sexual development ,blood pressure, social response, hunger, food, physiological clock, and endocrine state.

10. Migration of Hilsa Fish Hilsa is an estuarine or a marine fish. It lives in the water not far from the coast. It is available in the rivers 150 miles up in Bangladesh. It has several species: 1. Tenualosa ilisha 2. Tenualosa kanagurta 3. Tenualosa motius 4. Tenualosa tole

11. Two runs or two types of Migration of Hilsa are Recognized. 1. South – West Monsoon 2.Late Winter

12. South – West Monsoon

13. Late Winter Migration of Hilsa shad is not limited to monsoon only,but it also migrates short period during winter. It happens during the month of February to March.

14. Migration Patterns of Hilsa

15. Hilsa Migration in Bangladesh Source : DoF

16. Migration Route of Hilsa During Pre- Farakka Period

17. Trends in hilsa production during 1983-2008

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