Researchers discover new catfish species in Bhutan

The College of Natural Resources (CNR), Bhutan and Saint Louis University, USA in a collaborative research on fish diversity in the country, in October last year, has discovered a new species of torrent catfish from Khalingchhu in eastern part of Bhutan. It is an endemic species to Bhutan and found nowhere else. The fish was named Parachiloglanis “bhutanesnis” as it was first recorded in Bhutan. The fish was commonly known as Khaling torrent catfish.

R.J Thoni, a PhD student along a professor with CNR, Dr D.B Gurung, first conducted the scientific scrutiny and discovered the fish was never recorded before. They have confirmed that Parachiloglanis bhutanensis is not only a newly discovered species of torrent catfish from eastern Bhutan, but also the first endemic fish species to be described from Bhutan. The researchers discovered the endemic fish from a stream which is a kilometre east of Khaling, Trashigang.

When carefully studied, researchers found that the endemic fish has flat body with broad, blunt and rounded head, rising at roughly a 45-degree angle from snout to point vertical with eye. The researchers also recorded the fish as having other prominent features, such as thick and leathery fin, flat from snout to vent while from vent to posterior edge of anal-fin, angle raises equivalent to downward slope of dorsal surface at the same point on the body. However, the body angle is known to rise gradually upwards from posterior edge of anal fin to caudal-fin base.

The researchers say the unique ventral view of mouth and snout which resembles more of a hammer or bell than the body part of fish makes it an interesting fish. Such a shape, the researchers add, is due to the posterior flap of tissue connecting maxillary barbel to mouth.

Another breakthrough the studies have made is the genus Parachiloglanis was earlier recorded as having only one species P. hodgarti. This means that now there are two species under the genus. “But now, with the discovery of P. bhutanensis, the genus Parachiloglanis is no longer monotypic,” the scientists said, and adding that the two species have differences that are poles apart. “They differ in meristic, mensural, and coloration characters.”

Further, Parachiloglanis bhutanensis is confirmed as a member of the genus by the absence of a post-labial grove on the lower lip, which is present in other genera of the subfamily Glyptosterninae.

During their studies, R.J Thoni and Dr D.B Gurung found that the newly discovered endemic fish is known from Khalingchhu stream and an adjacent, unnamed stream in the headwaters of the Dangmechhu, in the Brahmaputra drainage. However, they didn’t rule out its presence in other streams in other parts of the country.

R.J Thoni and Dr D.B Gurung, in their scientific report, stated that Parachiloglanis bhutanensis was discovered in a high-velocity, small order stream 2211 metres above sea level. But unlike its congener in similar streams, they were found in low numbers. “Even with several hours of effort of trying to net as many live specimen as possible, we could collect only three specimens,” the researchers said, indicating that the fish is rare and does not occur abundantly.

Like its cousin, the newly discovered fish is known adhering to the bottom side of boulders, favouring areas of cascades and white water rather than pools. “They were associated with large rocks with deep undercut areas versus rocks with only small refuge from the current,” state the researchers. They also described the two streams in which they were found as having clear, cold-water environments, sourced from mountain springs, precipitation runoff, and snowmelt.

Hence, the streams are found to have little algal growth and frequent high-flow events. “This species is adapted to a high-velocity environment with adhesive striations on the leading rays of the paired fins for clinging to rocks and an inferior mouth adapted for scraping algae and invertebrates from the substrate”.

However, they described the discovery as very important and a milestone in conserving fish diversity of Bhutan. For instance, they pointed out that due to its small range and low density, as well as the highly stochastic and increasing nature of floods and droughts in streams of this region, P. bhutanensis may be a species of conservation concern.

Hence, the researchers hoped that further research will be conducted to determine its range and understand its biology and life history to ensure its existence far into the future. Doing so, they said will be beneficial in understanding and conserving the species in Bhutan.

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