Thank you for the invitation.

I am not specialist in this field and thus, I can not provide a professional answer.

From a brief investigation I found the attached links which may be useful.

Regards

http://link.springer.com/article/10.1007/s11160-004-3551-y

http://www.fao.org/docrep/004/Y2785E/y2785e03.htm

http://www.nwcouncil.org/history/damsimpacts

Thank you for the invitation.

I am not specialist in this field and thus, I can not provide a professional answer.

From a brief investigation I found the attached links which may be useful.

Regards

http://link.springer.com/article/10.1007/s11160-004-3551-y

http://www.fao.org/docrep/004/Y2785E/y2785e03.htm

http://www.nwcouncil.org/history/damsimpacts

Dams create calm bodies of water, changing overall temperature regimes and sediment transport, leading to conditions which tend to favour generalist species. Loss of specialist species, particularly endemics, changes the community structure and leads to biotic homogenization.  A dam will withhold sediment in the reservoir, not just decreasing the amount of substrate available to local freshwater species, but even impacting diadromous, estuarine and marine species much further downstream.  The competition between resident species for food and breeding sites will increase as damming isolates populations, and perhaps more importantly, damming completely restricts migratory fish species.  Isolation may lead to decreases in genetic diversity and therefore puts species at greater risk from disease.  All of these effects may be exacerbated by changes in the surrounding land use.  Overall, damming river flow will lead to both a loss of native species, but also an increase in exotic species which are more likely to become established in degraded habitats. For this reason, dams are one of the greatest global threats to freshwater biodiversity.

See in picture ----- A salmon jumping up a waterfall in Canada. Diadramous fish species often face mortality or reproductive failure when their migratory route is obstructed by dams.

https://freshwaterblog.net/2012/06/11/the-effect-of-dams-on-fish-biodiversity-a-global-view/

Dear all

Rivers possess a delicate ecology that depends on a regular cycle of disturbance within certain tolerances. The plant and animal communities that inhabit the river and river margins have evolved to adapt to their river's own peculiar pattern of flood and drought, slow and fast current. Dams disrupt this ecology.

 Fish passage is a concern with dams. Many fishes must move upstream and downstream to complete their lifecycles. Dams are often built without fish ladders. When fish ladders are provided, they seldom work as needed. If enough adult fishes do manage to climb above a dam, there remains the issue of their young: how will they get back downstream? Many are killed by predators while they wander in the slow waters of the reservoir above the dam. Many are killed in their fall downward through the dam to the river below. They aren't killed by the fall itself, but by the high levels of nitrogen gas at the base of the dam. In other words, like divers who go too deep, they get the "bends."

     There are many fishes that cannot climb dam ladders or leap over low dams. Some of these fishes swim upstream every year to breed, then let the water carry them back downstream. The eggs of pelagic spawners float downstream, too, which is why the adults must swim far upriver to breed. Otherwise, the baby fish would soon end up out to sea.

Well i can't tell exactly but i think it might affect but i think it is better to check the link below.

https://www.internationalrivers.org/dams-and-migratory-fish

Thanks Aristidis for your resourceful reply.

Dear Shankhadeep Chakraborty,

The number of fish stock, the level of reproduction and yield fluctuations from year to year are determined by a number of factors - changes within the year and from year to year, the hydrological regime, pollution of rivers, hydraulic and fishing. Review each of these factors requires independent publications. Here we note only that the fluctuations in water availability and associated disordered system of flood spill, causing many years catastrophic flooding of floodplains, as well as the absence of flooding in low-water years, the negative impact on fishing, hunting and other types of farms, based in floodplains. They are unfavorable as the absence or very low tide, or too high and prolonged floods, in which the deteriorating conditions of spawning and feeding fish. The best conditions for fish stock are created in the years of moderately high, timely and prolonged flooding.

On the number of fish stock very much influenced by the pollution of rivers and water bodies by industrial effluents, oil during its production and transportation, food timber rafting, resulting in many spawning grounds lost its role, and the River Fishery lost value.

Regards, Shafagat

I think it will because of the materials used in construction which may be toxic to fishes 

I believe that construction of dams can affect the reproduction of fishes. This is due to the flow of water and the material used in building the dams.

Thanks all.