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

A popular food fish in South Asia. Five types of ilish can be found worldwide.

Yearly ilish caught are 5,000,000 tons. Among them, 50%-60% are caught by Bangladesh.

About 450,000 people are directly involved with the catching for livelihood; around four to five million people are indirectly involved with the trade.

Tenualosa ilisha

Family: Clupeidae

Estuarine or a Marine Fish

Contributes 1% of GDP in Bangladesh

It is also the national fish of Bangladesh.

Common Names

• Hilsha• Palla Fish

• Ellis, Ilish• Ilishii

• ইলি�শ• Pallu machhi

Description and habitat

The fish is marine, freshwater, brackish, pelagic-neritic: Anadromous: Depth range-200 m.

Within a tropical range; 34°N - 5°N, 42°E - 97°E in marine and freshwater.

It can grow up to 60 cm in length with weights of up to 3 kg.

Food value

In Bangladesh and West Bengal during Pohela Boishakh ,it is customary to have ilish with panta bhat typically at breakfast.

The meal is the traditional way to celebrate the Bengali New Year. It is the National Fish of Bangladesh.

Migration And BehaviorMain 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.

Migration CircuitMost fishes have three points in their migratory circuit

A. The Feeding Ground

B. The Spawning Ground

C. The Nursery Ground

Diagrammatic Route of Migration Circuit

Adult Stock Feeding Ground

Spawning Ground Juvenile Nursery Ground

Denatant

DenatantDenatantContranatant

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.

Migration of Hilsa FishHilsa 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

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

2.Late Winter

South – West Monsoon

Hilsa fish mainly lives in the sea and around the monsoon, when consequent flooding of all the rivers and it is time to spawn.

Swims against the tide and goes back to the river where its mother had given birth to it.

Earlier, the Hilsa would move from the Bay of Bengal to Bangladesh rivers, the Padma, and the Meghna, for spawning.

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.

Migration Patterns of Hilsa

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Trends in hilsa production during 1983-2008

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