Depletion of Habitat of a Himalayan Fish May Signal Danger to Indus River

The second in an occasional series on the Indus River

Snow Trout is native to the Indus River in the Himalayas. This picture is of the Indus River in the outskirts of Leh, India on Oct. 9, 2020. (Venus Upadhayaya/Epoch Times)

LEH, India—The Indus River system sustains over 200 million people in Asia. But its ecosystem is fragile, and the depletion of the habitat of the Snow trout, a fish native to the river, warns of greater changes regarding the health of the river itself, according to experts.

The Indus originates in Tibet, crosses the disputed India-China border, meanders through Leh-Ladakh before entering the disputed territory between India and Pakistan in Gilgit, and finally flows through Pakistan before joining the Arabian sea.

There are over 20 species of trout in the Himalayas, according to Mohammad Ameen, the assistant director of the Fisheries Department in Leh. Six to seven of them are found in Indus’ tributaries in Ladakh like the Zanskar River, Shouk River, and Galwan River, the latter two were more in the news recently because of a bloody conflict that happened between India and China at a spot over a mile from where the two tributaries meet.

Since then there have been reports about China altering the Galwan River ecosystem to claim the region as its own. There are also reports of a dam built by China on the Indus, just 50 miles from Demochok in southern Ladakh on the India-China border. Within India and Pakistan, there are multiple irrigation and hydro projects on the river and its tributaries.

The Snow Trout, according to Ameen, is a cold water environment fish, and it needs temperature between four-degree Celsius and 18 degrees. If the temperature goes beyond this limit, it migrates to its temperature zones—the distance could be 62 miles (100 kilometers) upstream or downstream.

“Territorial boundaries don’t affect it. It migrates for feeding and breeding. When the water freezes in winters in Ladakh, it prefers downstream. In summers when the temperature downstream becomes higher, it migrates upstream,” said Ameen adding that this migration behavior of the Snow Trout is witnessed from Kailash Mansarovar, from where the Indus originates to the tributaries downstream and further within the river’s Himalayan ecosystem.

The population of Snow Trout is particularly threatened in the Himalayas because the “rate of warming” and the “glacier meltdown” is higher than elsewhere, according to the study “Is There Always Space at The Top” published in Ecological Indicators, an international science journal on Sept. 6.

The study says that the Snow Trout across all its habitats in the Himalayan range would lose up to 16 percent of its habitat by 2050 and up to 27 percent by 2070.

“As it stands, the snow trout faces serious threats due to river valley modifications, destructive fishing practices, and exotic salmonid introductions,” said the study. “Due to ongoing threats, its population size has been reduced drastically in Himalayan waters, hence listed as vulnerable in the IUCN (International Union for Conservation of Nature) Red List.” The IUCN red list is a global inventory of the conservation status of biological species.

Nitish Priyadarshi, environmentalist and assistant professor, Department of Geology, Ranchi University in Central India told The Epoch Times in a message on a chat platform that any threat to the Snow Trout is a threat to the Indus ecosystem as well as the ecosystem of the entire region.

“Leh-Ladakh and a large part of the Tibetan plateau is a desert area fed by Indus and its tributaries. Destruction of Snow Trout’s habitat indicates something serious for the ecosystem of the entire Indus River system,” said Priyadarshi. “It’s a signal for a future disaster.”

A bird's eye view of the Himalayas and a tributary of the Indus from a flight from Leh to New Delhi on Oct. 20, 2020. (Venus Upadhayaya/Epoch Times)

Depletion of the Trout’s Habitat

The Snow Trout’s preference for a specific temperature makes its habitat extremely prone to interference due to the construction of dams, bridges, and river diversions, according to experts.

“Fish populations are highly dependent upon the characteristics of their aquatic habitat, which supports all their biological functions. Fish require different environments for the main phases of their life cycle, which are reproduction, production of juveniles, growth, and sexual maturation,” said Priyadarshi.

“The construction of a dam on a river can block or delay upstream fish migration and thus contribute to the decline and even the extinction of species that depend on longitudinal movements along the stream continuum during certain phases of their life cycle,” said Priyadarshi.

Ameen gave an example of what happens to the Snow Trout population when a dam is constructed.

“When a barrage is constructed for a dam, the water slows down. This decreases the oxygen content of the water and the water depth increases. As a result, the sun rays penetrate less, and the temperature increases—thereby spoiling its habitat,” said Ameen adding that the construction of dams and river diversions is impacting other forms of life in the ecosystem as well.

Priyadarshi said that in dry mountain areas in the larger Tibetan Plateau region and in Ladakh, dam construction particularly causes extra sediment load in the river systems.

“Due to recent climate change, Leh-Ladakh area is receiving less rainfall which has decreased the water level affecting the production of fishes in the area,” he said adding that the depletion of the habitat of a single species like the Snow Trout, means changes in the entire ecosystem of a river.

A rainbow trout fish, an exotic species of trout in a tank in a government-managed fishery in the outskirts of Leh, India on Oct. 12, 2020. (Venus Upadhayaya/Epoch Times)

Himalayan Ecological Heritage

The Himalayas, an over 1550 miles long mountain range originated in three phases—the first upliftment happened in the Oligocene epoch, 35 million years ago, the second happened in the Miocene epoch, 15-25 million years ago and the third happened in the post-Pliocene period, about 10 million years ago.

The Snow Trouts’ history of origin dates back to its primitive ancestors that diversified and spread due to geological events that happened in the Miocene epoch, according to the study published in Ecological Indicators, on Sept. 6.

“Snow Trout is an ecological heritage of the Himalayas,” said Ameen adding that during its breeding and feeding season while it migrates, the fishing department prohibits fishing for it in specific areas.

Priyadarshi said that Indus is an ancient river fed by snows and glaciers of the Himalayas and to understand what’s happening with the river’s ecosystem and the habitat of fish like Snow Trout, there’s a need to look into the hydro-geological flow of the river and its drainage pattern in the last 200 years.

“The research into the hydro-geological factors like the rock type and typography would help to understand the factors impacting fish populations including the Snow Trout and vice versa. These hydro-geological factors like sedimentation, lessening water, and retreating glaciers have an impact on Snow Trout and the entire river ecosystem,” he said.

Priyadarshi said that the Leh-Ladakh and the entire Himalayan region is prone to earthquakes. “A little earthquake of even M6 can impact river flow,” he said.

“When glacier-fed rivers are dammed, they divert and then gradually disappear,” said Priyadarshi adding that those diverting and damming rivers for development and geopolitical supremacy don’t understand the implications of their actions.

“But a river is a geological phenomenon. And diverting or damming a geological phenomenon that has taken millions of years to evolve is not a small thing,” he said adding that the Snow Trout is just one variable in the larger picture of Indus ecosystem and there’s a need for an extensive study.