The first comprehensive study of the wild-caught trade in the Asian arowana (Scleropages formosus) in Cambodia has revealed a gloomy picture.
The study, conducted by Jodi Rowley, David Emmett and Seila Voen and published in a recent issue of the journal Aquatic Conservation: Marine and Freshwater Ecosystems based its results on interviews with 62 local villagers at four sites in Koh Kong province, south-west Cambodia.
In Cambodia, the spawning season of the Asian arowana lasts for about three months, beginning towards the end of the dry season (March"April), and with each male brooding an average of 30 juveniles orally.
Harvesters target the fry and juveniles because they are easier to capture and survive capture and transport better than adult fish, with most collecting taking place at night when fish are more easily located by scanning water bodies with powerful torches and looking for their characteristic eyeshine.
According to the authors, he main harvesting method involves killing or frightening brooding males into releasing their offspring. Once brooding male S. formosus are located, various methods are used to capture juvenile fish. Respondents indicated that spears, knives, firearms, explosives, cast nets, gill nets and electrofishing were used to kill or frighten adult S. formosus.
However, in the last 5"10 years, many harvesters have become aware that killing adult fish will decrease future populations, and reported that harvesting methods that are lethal to adult fish are now less common.
The harvested fish are sold for an average of US$11"13 per juvenile. The fish are then transported through a series of larger towns, with most ultimately bound for Thailand for further re-export.
The effect of the harvest and trade in Cambodia has been devastating local populations of the Asian arowana.
Arowana harvesting in Singapore
Matt Clarke shows off a set of pictures taken by Neil Hepworth which show how arowana fry are harvested on Singapore fish farms.
The authors continue he current number of S. formosus harvested from the wild in Cambodia is almost certainly highly unsustainable, and it is likely that a number of populationshave already become extinct. As long as there is a demand for S. formosus, it is likely that local people will continue collecting juveniles because of the high prices obtained per fish.
A single brood of 30 S. formosus juveniles is likely to earn a harvester $US300"500, which is a substantial amount given that almost 80% of the Cambodian population lives on less than US$2 per day. Without proper management, it is likely that further S. formosus populations in Cambodia will become locally extinct.
The authors conclude with a dire warning that harvesting for the aquarium fish trade is not the only problem faced by this species in Cambodia: ...the freshwater habitat of S. formosus is coming under rapidly increasing pressure from road development, agricultural expansion, logging, hydroelectric dam development, and mining.
Most of the river systems in Cambodia known to contain wild populations of S. formusus are now under threat from hydroelectric dams. These activities are likely to have a much greater impact on S. formosus populations than harvesting by local people.
For more information, see the paper: Rowley, JJL, DA Emmett and S Voen (2008) Harvest, trade and conservation of the Asian arowana Scleropages formosus in Cambodia. Aquatic Conservation: Marine and Freshwater Ecosystems 18, pp. 1255"1262.