Denison barb  (Puntius denisonii)

The Denison barb is classified as Endangered (EN) on the IUCN Red List (1).

One of the most popular ornamental fish species in international trade, the Denison barb (Puntius denisonii) is an endangered and endemic fish of the Western Ghats, India (3). It is easy to see why this species has been in such demand, with its attractive colouration of silvery scales across the body, silvery-blue fins and bluish tail with black and yellow tips (4) (5).

The most distinctive feature of this freshwater fish, however, is the black stripe that runs along the length of the body, as well as the striking red stripe that stretches from the snout to the middle of the body (4) (5). Like other barbs, the body is torpedo-shaped, with the base of the tail being relatively fat, while a pair of barbels, equipped with taste organs, hang from the lower lip that are used to find prey in murky water (5) (6).  

The Denison barb is endemic to the Western Ghats of India where it is known from only eleven rivers (1) (7).

The Denison barb inhabits fast flowing hill streams with thick vegetation along the banks, where it is most often found in rocky pools (1) (7). 

An active and social fish, the Denison barb collects in small, fast moving shoals (1). Although largely placid, at times this fish can be more aggressive, particularly when feeding (5). The diet of the Denison barb is unknown, but most cyprinids will eat almost anything they can find, including detritus, algae, molluscs, insects and crustaceans (6).

This egg-laying species spawns during the monsoon, between November and January, with the juvenile fish maturing from May to July the next year (4) (6). It is likely that these fish have a lifespan of up to eight years (5).

One of India’s most celebrated ornamental fishes, the Denison barb has suffered huge declines as a result of its popularity. In the absence of catch limits, the single most significant threat to this species is unsustainable collection for the pet trade. It has declined at an alarming rate of around 70 percent since 2004 and is now reduced to highly fragmented, relict populations (1) (3) (4) (8).

This species was first exploited in 1996, when India began exporting it to Europe, with demand for the species rapidly increasing thereafter. Between 2007 and 2008 alone the Denison barb accounted for 65 percent of ornamental fish exports from India, with the value of this trade worth around US$ 1.5 million (7).

These fisheries have been highly selective for the more attractive juveniles, limiting the number of fish reaching an age at which they can reproduce, while they may have also inadvertently caused a sex ratio skewed towards males, and reduced the species’ genetic diversity (1) (9). Those remaining populations are further threatened by deforestation, mining, agriculture, hydroelectric projects and urban expansion, all of which reduce water quality, and the degradation of habitat by the use of dynamite fishing and plant poisons for larger fish species  (1) (7).

A conservation priority for the recovery of the Denison barb is to reduce the number of fish caught in fisheries, as at present this is likely unsustainable. The Government of Kerala has introduced regulations for catch limits and restrictions on the use of fishing gear, while plans have been developed for designated no-take zones and specific Denison barb sanctuaries. The listing of the species on India’s National Wildlife Protection Act should also ensure that trade is carefully regulated (7).

The Denison barb breeds successfully in captivity, with Chester Zoo the first aquarium to breed the species naturally, and there is hope that the trade in captive-bred fish can reduce the pressure on wild populations (5) (7). In addition, further studies on the species’ biology and population are needed if informed conservation measures and management strategies are to be implemented (1) (4) (7).

For more information on the conservation of the Western Ghats, India, see:

• WWF:
  http://wwf.panda.org/what_we_do/where_we_work/western_ghats/
• Wildlife Conservation Society:
  http://www.wcs.org/saving-wild-places/asia/western-ghats-india.aspx