classification of fishes based on migration in dams in india

Sourav PanDecember 20, 2024

Answered

Fish migration is a critical aspect of aquatic ecosystems, significantly impacted by the construction of dams. In India, the classification of fish based on their migratory behavior can be understood through various categories, primarily focusing on diadromous and non-diadromous species.

Types of Migratory Fishes

1. Diadromous Fishes: These species migrate between freshwater and saltwater environments. They are further classified into:
   • Anadromous Fish: These fish spend most of their lives in the ocean but migrate to freshwater rivers and streams to spawn. Examples include salmon and trout.
   • Catadromous Fish: These fish live primarily in freshwater but migrate to the ocean to spawn. An example is the eel.
2. Non-Diadromous Fishes: These species complete their life cycle entirely within freshwater systems. They do not migrate to saltwater environments and are significantly affected by dam constructions that disrupt their habitats and migration routes.

Impact of Dams on Fish Migration

Dams have a profound impact on fish migration patterns in India, leading to habitat fragmentation and loss of connectivity in river systems. Key findings from recent studies include:

• Fragmentation of Habitats: India has one of the most fragmented fish habitats globally, with over 5,264 large dams affecting fish populations. This fragmentation disrupts spawning and feeding grounds for many species.
• Genetic Isolation: Species like the golden mahseer experience genetic differentiation due to barriers created by dams, which inhibit their natural migration routes. This isolation can lead to reduced genetic diversity and increased vulnerability to extinction.
• Need for Fish Passes: The construction of fish passes (or ladders) is crucial for facilitating the movement of migratory species past obstructions created by dams. However, many existing dams lack effective fish passes, which hinders migration and affects population dynamics.

Conservation Efforts

To mitigate the adverse effects of dams on fish migration, several conservation strategies are recommended:

• Designing Effective Fish Passes: Future dam projects should incorporate well-designed fish passes that accommodate the specific needs of migratory species, ensuring they can navigate around barriers effectively.
• Restoration Projects: There is a call for restoration efforts, including the removal of certain dams or modifications to existing structures to enhance ecological connectivity in river systems