Alien fish species have been known to make their presence in our dams, lakes and rivers but not much attention has been paid to their existence. Piranhas, African catfish, pirarucu (Arapaima gigas), peacock bass, and tilapia, to name a few are all found in abundance in our waterways, and some are bred in ponds for the aquaculture projects.
Of late, news has surfaced of the discovery of two new foreign predatory fish known as the earth eater and the black ghost knife fish. The situation is grave because of warning from experts about the ecological disasters from these aquatic nuisance species. Ecosystems around the world have been dramatically altered as fish species are shifted around, whether for commercial fishing stock, or the aquarium trade.
Humans are experts at helping species move from their native habitat into new territory. The new habitat may suit the invader fish so well that the results are catastrophic for local species. They are able to multiply at a very rapid rate and in the absence of a predator they are wiping out many of our native river species.
Species are transported around the world to fish farms, and when they escape, become naturalised in many areas causing damage to native species and habitats. Recreational fishing is also to blame for the spread of invasive species. Trade in alien species for aquarium use can result in marine invasions with people keeping exotic fish, marine plants, invertebrates or corals in aquariums. Once fish hobbyists have outgrown their fetish, or find their fish to be unmanageable when big, they are then released into streams and lakes.
It may seem like the humane thing to set Nemo free in the ocean but such impulses pose an enormous threat to native ecosystems. Even something as seemingly harmless as a goldfish can disrupt local food webs by preying on fish eggs and small invertebrates, cause excess algal growth by rooting up plants and releasing nutrients and others.
Anglers, usually ignorant of biological processes, assume that adding more fish to a river, dam, or lake is somehow helping nature. Certain freshwater fish species used for recreational angling are released into rivers, dams and lakes without an environmental impact assessment or monitoring for the sole purpose of providing enjoyment for anglers. This practice has become so widespread that people often think that some of the invasive species are actually native ones.
At a UN conference on alien species in Norway in 1996, experts from 80 countries concluded that “alien invasive species were a major threat to biodiversity conservation and probably the greatest threat after habitat destruction.”
The fight against invasive species is a losing battle because eradication is impossible for many of these invasive species as they are already established beyond control. Also, the general public does not know or care about invasive species, and also there is an absence of preventive behaviours to be effective.
Management of invasive fish species requires urgent attention and Sahabat Alam Malaysia (SAM) calls on the Fisheries Department to:
· Enforce the law in dealing with those found to be importing, selling and keeping alien predator fish;
· Halt the introduction of alien species solely for the pursuit of pleasure; and
Community participation and awareness are critical to prevention to halt the spread of invasive species.
Letter to Editor, 25 June 2018