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species suddenly disappear from the system, demand detailed ecological investigations. We tried to understand the “intentional” safeguarding of native species by the nature and came up with explanation that suddenly started making sense to the Priority Effects principle. Continuous natural modifications of the river hydrology over the years make the native fishes much more resilient to natural stochasticity, thus, helping in their retention. Nevertheless, there is a condition to it, failing which nature would not act! The river must be “undammed” and its flow unobstructed by human interventions.
Studies, though less in number, across other undammed basins of the globe have detailed the priority effects principle eradicating “just” the invaders. Damming, however, has reversed the eradication choices! In various dammed rivers, natives have eventually gone locally extinct, while the invaders have been flourishing at a faster pace. A stable habitat provided by the dams is seamlessly controlled, even under extreme hydrological events. This results in favourable conditions for the invaders. Now if you ask, why do the natives suffer? The reason is quite clear alteration in their natural habitat. With damming, it is not the
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nature, rather we who decide when and how muchthewaterflowsintotheriver.Thenatural habitat and seasonal flow characteristics act as indicators or “phenological cues” governing the spawning (breeding) times for native fishes. Acting as dependable guides, they say, “Hey natives! This is the safest time for you to bring in your young ones into the world!” By building up dams, we are messing up with these natural cues eventually leading to a poorer native stock, and then with the presence of ever-adaptive, super-active invaders, life gets tougher for them! The native numbers in many dammed basins on Earth are plummeting, a situation grave enough.
By extirpating the invaders from Asiganga, nature has cleaned a system which we could not for more than a century. Nature, however, will not always give us second chances. Taking lessons from the Asiganga priority effects we must ensure that we don”t fall a prey to our greedy motives of commercial gains by promoting the invaders. The brown trout must notbestockedbackintoAsiganga.Asnature sustains itself only if we leave it undisturbed, we need to identify undammed rivers across the Himalayas and make sure they are left free flowing and pristine.