Fish Profile: The Denison Barb (Sahyadria denisonii)



The Western Ghats is a mountain range that spans 160,000 square kilometers along the western coast of the Indian peninsula. This mountain range is reported to be older than the Himalayas and is home to an enormous proportion of India’s biodiversity. Endemic to the rivers of the Western Ghats is our featured fish, Sahyadria denisonii, the Denison barb, or roseline shark.


S. denisonii was described to western science by Francis Day in 1865. Day was a prominent ichthyologist in British controlled India, and would become the Inspector-General of Fisheries in India and Burma. He named S. denisonii after Sir William Thomas Denison, the governor of Madras, India from 1861 to 1866.


Over a hundred years later, S. denisonii soared in popularity in the mid 1990’s and by 2007 made up 60% of the total live ornamental fish exported from India (Raghavan 2009). This volume of exportation, coupled with lack of regulation, resulted in S. denisonii’s current status as an endangered species as of 2010. Wild populations have dropped by more than 70% since 2006 at key collection sites (Kurup and Radhakrishnan 2006).


Today, If you find S. denisonii in an aquarium store, it probably was not caught in the rivers of the Western Ghats. The government of Kerala, India instituted management practices to protect S. denisonii. These include fixed total allowable catch, restrictions on gear size, closed seasons, and “no take zones” (Mittal 2009). The closed season as of 2010 was declared to be June, July, and October. These months were thought to be when spawning took place. However, it is more likely that spawning occurs from October to March and the closed season should reflect this (Solomon et. al. 2011, Manoj et. al. 2010).


As of 2010, captive breeding practices were developed by researchers and hobbyists, but lacked commercial scale (Manoj et al. 2010, Mathew 2008). Today, commercial operations have increased and the environmental stress of S. denisonii’s popularity is starting to wane. However, the region this fish is from is still a biodiversity hotspot, meaning human encroachment still threatens wildlife on a significant scale.


Be sure to ask your local fish store from where they source their S. denisonii. There have been reports of captive bred fish being exported from Indonesia and Singapore (Mittal 2009). However, if your local fish store buys from an exporter sourcing directly from wild caught specimens in India, consider the ethical and environmental ramifications of your purchase and how you want to represent your corner of the aquarium hobby.


Description

S. denisonii have a striking coloration. They have a black line running from the snout to the caudal (tail) fin, boarded above by a sharp red line which runs halfway down the flank. They have a vibrant red coloration on the dorsal fin, and yellow spots with black tips on the caudal fin.


It is difficult to visually sex males from females. Although females are reportedly incrementally larger, with heavier bodies, and sometimes duller in coloration than males.


S. denisonii has an average maximum standard length of 3.5 to 5.5 inches.


Habitat

S. denisonii is found in three major rivers in the Western Ghats mountain range. They inhabit the benthopelagic (bottom water column) of the fast flowing hill streams and tributaries of these rivers. Their torpedo body shape makes them hydrodynamic. They spend most of their time amongst rocky bottom pools and sandy, graveled, and cobbled runs and riffles, surrounded by overhanging vegetation (Prasad 2007, Radhakrishnan 2006, Raghavan et. al. 2009, Biju 2005).


A river is made up of runs, riffles, and pools, each occurring after the other as the river meanders. Pools have slow flow and occur at the peak of a bend. Runs are fast flowing and occur as the river straightens out. Riffles are also fast flowing and are the shallowest portion, often rippled from the bottom substrate and lead into pools. S. denisonii is found in all these microhabitats.


Aquarium Habitat

S. denisonii is a shoaling species and should have plenty of open space in which to swim. They should live in groups of 6 to 10 and are very friendly with each other. They will spend most of their time along the bottom of the aquarium in partial open water. At least 30% vegetation is recommended to mimic their natural habitat and provide cover.


Aquarium Water Parameters

S. denisonii does well in community tropical aquariums. They thrive in a normal temperature range of 68 to 77 degrees Fahrenheit, and do well as low as 60 degrees. Being from colder, well oxygenated, headwaters, they prefer lower temperatures and high dissolved oxygen.


They prefer a pH of 6.5 to 7.8, alkalinity of 4-8 dKH and a general hardness of 5 to 20 dGH.


S. denisonii does best in pristine water with low organic waste which mimics the fast flowing streams they live in. They are adaptable to most other parameters, but remain healthiest when organic nutrient levels are low. Regular water changes, excellent biological and chemical filtration, and live plants will help keep water pristine.


Diet

S. denisonii are omnivores, favoring worms, insects, crustaceans, plant material, and some organic debris in the wild. In the aquarium, you should feed a high quality sinking pellet or flake food, supplemented with animal protein from bloodworms, daphnia, or Mysis shrimp.


Because they spend most of their time near the bottom, sinking food is best. To make flakes sink, simply break them up in between your fingers and submerge your fingers and the broken up food in the water for a couple seconds then release. The flakes will scatter in the flow of the filter and circulate throughout the water column. If you sprinkle the whole flakes on the surface, they will float for some time before eventually sinking.


Breeding

S. denisonii were first captively bred on a larger scale in southeast Asia and eastern Europe using growth hormones.


There have been a few reports of successfully breeding S. denisonii in captivity without the use of hormones. In 2005, the German magazine Aqualog suggested the continued lowering of pH may induce spawning. Another hypothesis from the Chester Zoo Aquarium in England showed successful breeding took place only in large groups. One factor that may lead to poor reproduction in captivity and the wild is a higher male to female sex ratio, which reduces the total number of eggs, or fecundity, available at any given time (Solomon 2011).


Regardless of how captive breeding is developed, limiting the number of specimens taken from the wild is crucial to keeping this species from becoming naturally extinct.


pH

6.5 - 7.8

General Hardness

5 - 20 dGH

Alkalinity

4 - 8 dKH

Temperature

60 - 77 degrees F

Preferred Lighting

Medium to High

Maximum Length

5.5 inches

Tank Size

60+ US gallons

Disposition

Non-aggressive


Fish Keeping Responsibly

S. denisonii is a prime example of a species that caught the human eye with its beauty and peaceful nature to its own detriment. Harvested far beyond sustainability, S. denisonii alone accounted for $920,000 US annually in India’s live ornamental fish exportation (Mitall 2009).


Many of the advancements that have taken place in the captive breeding of this fish occurred from independent researchers and hobbyists. It is not beyond the realm of possibility for you or I to help S. denisonii and other endangered species by furthering the hobbies’ knowledge of how to breed this species.


The best way to accomplish this is to research what has been done already, try to recreate the circumstances in which successful breeding occurred, and most importantly, record and share your results.


Sources

Biju, C.R. 2005. Habitat and Distribution of Hillstream Fishes of Northern Kerala (north of Palghat Gap). Zoology, Mahatma Gandhi University.


Kurup, B.M and Radhakrishnan, K.V. 2006. Indigenous ornamental fish resources of Western Ghats with special reference to Kerala. Souvenir of Ornamentals Kerala 2006, International Seminar on Ornamental Fish Breeding, Farming and Trade. Department of Fisheries, Government of Kerala, Cochin, India.


Manoj, C.K., Nair, C.M., Salin, K.R. and Pillai, D. 2010. Captive breeding and embryonic development of Puntius denisonii, an endemic ornamental fish in the rivers of the Western Ghats, Kerala, India. Fishing Chimes 29(12): 18-21.


Mittal, R. 2009. Business unusual: Conserving Miss Kerala. Aquarama Magazine 12: 7-9.


Prasad, G., A. Ali and R. Raghavan, 2007. Threatened fishes of the world: Puntius denisonii (Day 1865) (Cyprinidae). Environ. Biol. Fishes


Radhakrishnan, K.V. and Kurup, B.M. 2006. Distribution and stock size of freshwater ornamental fishes of Kerala (S India) with special reference to sustainabilty issue. In: Kurup, B.M and Ravindran, K. (eds), Sustain Fish - International Symposium on Improved Sustainability of fish production systems and appropriate technologies for utilization, pp. 589-605. Kochi, India.


Raghavan, R., et.al. (2009). Damsel in distress - The tale of Miss Kerala, Puntius denisonii (Day), and endemic and endangered cyprinid of the Western Ghats biodiversity hotspot (South India). Aquatic Conservation: Mar. Freshwater Ecosystems, 19, 67-74.



Solomon, S., et. al. (2011). Reproductive biology of Puntius denisonii, an endemic and threatened aquarium fish of the western Ghats and its implications for conservation. Journal of Threatened Taxa 3(9): 2071-2077.


Photos
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  • https://www.responsiblevacation.com/vacations/western-ghats/travel-guide

  • https://www.healthyheadwaterslab.ca/hhl-news/riffle-pool-run


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