Suckerfish: Darling of aquariums, terror of open waters

By: Staff Reporter
Pterygoplichthys or commonly known as Janitor fish or sailfin armoured catfish and popular in India as suckerfish have severely invaded inland water bodies in India.

Native to the streams, floodplain lakes and marshes of South America, the suckerfish (scientific name: Pterygoplichthys) have successfully invaded inland water bodies of various countries across the world, including India.

Pterygoplichthys or commonly known as Janitor fish or sailfin armoured catfish or sailfin plecs or popularly in India as suckerfish, can be differentiated from their close cousins due to their large dorsal fins with 9 or more dorsal fin rays, which gives them their common name “sailfin catfish”. These fish have rows of armour plating covering the body and are adapted to survive without water for more than a day. These popular aquarium fishes are used in tanks by the fish hobbyists to clean the algae attached to the glass plates.

Armoured catfishes have established natural populations across India and the reasons for their successful invasion include their ability to toleration of poor oxygen content in water by means of accessory respiration, lower number of predators and less vulnerability to predation due to absence of natural predators in India. Invasive Pterygoplichthys, being large and bewilderingly resilient species, is likely to outcompete the native algae consumers, aggressively drive them away, and consume the eggs of those species and others. The effect of these invading armoured catfishes on the indigenous fish stock in India is not clear and therefore warrants further studies.

Photo Credit- Dr. A. Bijukumar

Therefore, more systematic studies/risk assessments are warranted in India to document the socio-economic and environmental effects due to the invasion. In South America, this suckerfish and the value added products from them have been used extensively as a high quality food. As the first step in the process of eradication of this nuisance species, exploiting these fishes as food can be tried in India, especially in those regions where they have established successful populations.

Dr. Biju Kumar, Head, Department of Aquatic Biology & Fisheries, University of Kerala says that a survey conducted among the ornamental fish traders and hobbyists in Thiruvananthapuram city revealed an interesting fact while the specimens grow in size, the traders and hobbyists find it difficult to keep them in tanks and therefore resort to release them into the natural drainages. Further, these suckerfish have now invaded the water bodies connected with drainage channels of Thiruvananthapuram city, such as Veli Lake and Karamana River, besides reports from Vellayani lake. Further, this suckerfish has also been reported from many other water bodies in Kerala and whether they established bigger populations is the matter to be investigated.

Fig. 5
Photo Credit- Dr. A. Bijukumar

Controlling invasive species can be difficult, but the best method to prevent introduction is through policy making and education. There is an urgent need for a legislation to prevent the release of ornamental fishes and potentially damaging cultivable alien species into the natural bodies and to formulate programmes to return the unwanted pets to the aquarium traders as a precautionary principle. Further, awareness materials should be developed in local languages, explaining the ecological implications of this species, specifically targeting students, aquarium hobbyists and fish breeders, as this exotic species seems to the be the fast invading species in the aquatic systems of India including river Ganga and Yamuna.

The researchers hypothesise that there may be possible hybridisation in aquariums or in fish farms or in the wild, but this needs to be found out aided by detailed studies incorporating different molecular markers and with sequences of topotypes or suckerfish from their natural streams. There are reports that the hybrids show much vigour in invasion and in countries likes USA these fishes are termed ‘nuisance’ species, considering the extensive damages caused to the systems and biodiversity.

Bijukumar, A., R. Smrithy, U. Sureshkumar & S. George. 2015. Invasion of South American suckermouth armoured catfishes Pterygoplichthys spp. (Loricariidae) in Kerala, India – a case study. Journal of Threatened Taxa. Vol. 7(3). pp 6987-6995;

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