Page 245 - AWSAR 2.0

also has a colonial history linked to it. Britishers as they colonized various parts of the world, brought along with them reminders of their home, the brown trout, which synchronizing with the British expansion, burgeoned into river systems far beyond its natural home range. This fish, listed in “100 of the world’s worst invasive alien species”, was also introduced in Lake Dodital by late 1860s, it eventually spread into Asiganga and established a viable wild population.
Now that we know of this invader’s past and how these uninvited guests came into our natural systems, let us peep into how the native fauna reacted to it. The brown trout had a single competitor for space, the native snow trout. The native, an herbivore and an icon of cold water Himalayan streams, the snow trout was a Himalayan endemic, which co-evolved with the Himalayas. So basically, when the snow trout speaks to the Himalayas, “Hey! I have seen you grow!” the mountain
chain replies “Likewise!” Co-
evolution as we predispose,
is not always interspecific,
rather there are instances
where a species evolves with
the changing geomorphology
of a landscape. Such is the
case with our snow trout,
which has continuously, yet
gradually evolved the adhesive
structures on its mouth to help
adhere to rocks and bear the
torrential flow patterns as the
Himalayan rivers changed
their hydro-morphology since
times immemorial (precisely
speaking!! the first interglacial period).
As the brown trout coloniszed Asiganga, the invader wreaked havoc on the snow trout population! Being a carnivore, it predated upon the snow trout young ones. With its active breeding strategy, it out-competed the
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native population, restricting them to isolated tributaries of major rivers - a finding confirmed by our research on other river basins! Being a commercial species, manual removal of this invader from the system was never considered. When humans come into play, often selfish needs ruin the natural balance of an ecosystem. And it gets even tougher if it is an invasive species. Nature, nevertheless, always overrides us, whether we want it or not. This could happen even if the slightest spec of “naturalness” in a system still remains.
The day, August 3, 2012 was a black one for the residents of Asiganga basin, when stronger-than-ever flash flood shook the area. It took a toll on human lives (n=35) and property (61,244.12 lakh). As the river discharge increased five-folds from 135 to 2665 m3/sec in merely an hour, the roar of Asiganga that night was horrific. The snow trout had since ages been yearning for some miraculous help
from the heaven. It often spoke to the Himalayas, “Oh Mountain so high! Your rivers quench the thirst of all humankind and provide safe haven to all plants and animals, which dwell in them... Answer my cry...Who saves me now? The humans have added this river monster which is feeding on my children, I can hope for nothing but a miracle, a miracle from Mother Nature!” As Asiganga soared high on that dreadful dark night, no one knew that there were switchovers taking place under the river surface! Nature
had already played its part. Taking the natives in its arms, it said, “Do not fear Oh Snow Trout! When humans create a disbalance, sooner or later I come to the rescue! I have pushed the invader out of your abode. You are in now safe hands, and so are your children!” The invasive
Inaccessibility is often deemed to be the reason for inadequately explored high-altitude Himalayan rivers, the biodiversity of which yet remains unaccounted for. Ironically, however, most
of these rivers have been profoundly explored by the human race for hydropower generation!