Wild waters: A glimpse into the hidden world of Bangladesh’s hillstream fish
Hillstream fish thrive in the fast-flowing, oxygen-rich, cool waters of our eastern hill tracts — represent a stunning diversity of life. Yet, these freshwater wonders remain largely in the shadows in our conservation conversations — out of sight, and increasingly, out of time
I stood still beside a shallow forest pool, my path ahead blocked by ancient boulders, worn smooth over centuries by the stream that threaded through. I hesitated, weighing the challenge of scaling those slippery rocks, already weary from the morning hike to set camera traps deep within the forest. Overhead, sunlight filtered through the canopy, casting golden ripples across the crystal-clear water. I tried to turn my attention to the pool.
Darting between rocks and resting in calm eddies, a multitude of fish drifted in and out of view — some small and silver, others striped in copper, or ink-black bands. Their silver scales and vivid stripes shimmered like moving brushstrokes.
They moved with grace, perfectly adapted to the pool's flowing water. In that quiet moment, it was clear: This was not just water — it was a living archive of evolutionary artistry.
Hillstream fish — those that thrive in the fast-flowing, oxygen-rich, cool waters of our eastern hill tracts — represent a stunning diversity of life.
Keep updated, follow The Business Standard's Google news channel
Species like Schistura, Garra, and Psilorhynchus have evolved to cling to rocks, skim the current, and forage on the streambed in ways that reveal a quiet mastery of their niche. Meanwhile, others like Devario, Barilius, and Danio live as torrent swimmers.
Yet, these freshwater wonders remain largely in the shadows in our conservation conversations — out of sight, and increasingly, out of time.
What lives in these streams?
The forested hill streams of Bangladesh, especially in the Chattogram Hill Tracts and parts of Sylhet, are home to at least a hundred specialist cold-water species found nowhere else in the country. These include rock dwellers like the banded loaches (Schistura spp.), the flat-bodied torrent minnows (Psilorhynchus group), and several Garra species with adhesive suckermouths used to grip the slippery substratum. Some are strikingly coloured, with iridescent scales or flame-like fins that rival even the most prized ornamental fish.
Despite this diversity, baseline data on these species remain patchy.
Many stream fish have never been photographed alive in the wild, let alone studied in detail. There are species yet to be described scientifically.
Identification challenges, lack of surveys, and low institutional prioritisation have left this entire group scientifically underrepresented.
A glaring gap in research and conservation
The conservation narrative in Bangladesh has historically centred around flagship species — tigers, elephants, or hilsa. Fish, when mentioned, are often lumped into discussions of aquaculture or overfishing.
But hillstream fish exist outside these frames. They are neither commercially farmed nor widely consumed, and their habitats lie in difficult-to-reach terrains. As a result, they are rarely on the radar of policymakers, researchers, or conservation NGOs.
The government's primary fisheries research body, the Bangladesh Fisheries Research Institute (BFRI), continues to emphasise induced breeding of so-called "native species". While this has had some success — for instance, the recent breeding of Crossocheilus latius — efforts remain narrowly focused on captive propagation.
There is little or no parallel action to study, conserve, or restore the wild habitats these species depend on. Where would we release these fish if their habitats no longer exist? Have we already decided to confine them to farms?
While BFRI's induced breeding trials make headlines, core threats remain unresolved: sedimentation from road construction, pesticide runoff, deforestation, sand mining, and waste dumping in hill streams.
I witnessed heavy pumps hauled deep into the forests of Rema-Kalenga to drain pools and catch everything in sight. Poison fishing, electrofishing and bomb-fishing are commonly practiced in the Chattogram Hill Tracts.
Even iconic species like the goonch catfish (Bagarius) — a legendary predator of South Asian oxygen-rich rivers — are dwindling due to river fragmentation and pollution. Yet, no conservation plan targets their survival in situ.
The aquarists stepping in
Ironically, some of the most important recent discoveries and observations have not come from institutions, but from amateur aquarists and citizen scientists. These hobbyists, often motivated by a passion for native fish, have documented live behaviour, colouration, and microhabitat preferences in ways the scientific community has largely overlooked.
In 2022, photographer and aquarist Jubair Tanvir documented and helped bring attention to Neolissochilus stevensonii, a spectacularly coloured hillstream cyprinid found in remote sections of the Sitakunda Range.
I recall my conversation with KH Newaz, another dedicated enthusiast. The photos he sent me around six years ago were the first reported instances of Pillaia indica, a rare and obscure species of worm eel in Bangladesh. These are just a few examples of the recent contributions by the aquarist community.
Despite their significance, these observations have received little institutional acknowledgement or follow-up. The data remain in Facebook groups, private messages, scattered blog posts, or private photo libraries — important work, but disconnected from national research priorities.
Why it matters
Hillstream fish are not just pretty or interesting. They are crucial ecological indicators. Their presence often reflects clean, fast-moving water and stable forested watersheds. The moment these streams are degraded — by dams, land clearance or sewage inflow — the fish disappear.
And they are not alone in their dependence.
Otters, for example, particularly the Asian small-clawed otter (Aonyx cinereus), depend heavily on hillstream fish populations. If the base of the food web collapses, these charismatic mammals will not be far behind. The same is true for stream-dwelling birds, reptiles, and amphibians.
In essence, protecting hillstream fish is not just about ichthyology — it is about preserving entire freshwater ecosystems.
What needs to change?
Hillstreams are Bangladesh's quiet frontiers — biologically rich, ecologically essential, and deeply under threat. Protecting them is not just about saving fish. It is about maintaining the very veins of our upland ecosystems. It is about safeguarding the futures of species like the otter, the kingfisher, and the stream frog. It is about recognising that even the smallest finned creature deserves a chance to swim free, in waters that remain wild.
Bangladesh urgently needs a shift in how we approach freshwater biodiversity, particularly in hillstream environments. National institutions should recognise and partner with local researchers and citizen scientists to map the diversity of hillstream fish, using both traditional methods and modern tools like eDNA.
Efforts should focus on maintaining stream health — preventing deforestation, regulating construction near streams, and controlling pollutants, not just on manual-based induced breeding techniques.
Agencies like BFRI must broaden their mandate beyond induced breeding to include in-situ conservation, environmental flows, and habitat protection. Contributions from aquarists should be acknowledged, supported, and integrated into formal conservation planning.
The broader public remains unaware of these hidden treasures. Visual storytelling, local museum exhibits, and school curriculum integration could raise awareness and inspire protection.
A closing thought
The striped minnows dance between shadow and sun in that hillstream pool and the otter feeding stations I spotted nearby exude a harmonious synergy. While watching, I could not help but feel a sense of awe — and urgency. These species have survived millennia of natural changes yet may not survive our indifference.
Hillstreams are Bangladesh's quiet frontiers — biologically rich, ecologically essential, and deeply under threat. Protecting them is not just about saving fish. It is about maintaining the very veins of our upland ecosystems. It is about safeguarding the futures of species like the otter, the kingfisher, and the stream frog. It is about recognising that even the smallest finned creature deserves a chance to swim free, in waters that remain wild
