Posted: Nov. 18, 2011, 8:15 p.m. EST
From Demon to Angel?
By John Dawes
Alien species are frequently regarded as pests that invade habitats, destroy the local natural equilibrium, drive native species to extinction or place them under threat, and cause major problems all-round. This, of course, is true of many such species. Take, for example, the worldwide explosion of rabbits, or the spread of the grey squirrel in the U.K. to the detriment of the native red squirrel.
There are also examples of widespread damage caused by some fish, one of the most notorious being the disastrous effects of the Nile perch (Lates niloticus) on the endemic Lake Victoria haplochromine cichlid population following its planned introduction in 1954. Another fish that has attracted headlines in recent years has been the pleco—although it’s not always clear which species is being referred to...or if there is more than one.
If we are talking about Hypostomus plecostomus, this large (up to 20 inches) suckermouth catfish was introduced into several countries where it is bred for home aquaria. Aquarium escapes or releases have happened over the years, with established populations officially recognized in Bangladesh, Florida, Texas, Thailand, Vietnam, Malaysia, Taiwan, Sri Lanka and the Philippines. The status of exotic populations of the species in Singapore, Hong Kong and China is unknown, while the population in the U.K., which received introductions from Asia in 2000, is, as yet, not established.
Surprisingly, FishBase.org does not list Mexico as receiving introductions of plecos, although their presence was first detected in 1995 in Río Mezcala. Since then, they have been recorded in Tabasco, Chiapas and Michoacán. Ever since they found their way into the lake created by the construction of the Infiernillo Dam (located between the states of Guerrero and Michoacán) in the early 1960s, plecos reproduced at a spectacular rate, to the extent they are considered a threat to the nation’s freshwater fisheries.
Now, in a novel “if you can’t beat them, eat them,“ approach, a study—carried out by a team from the Instituto de Investigaciones Agropecuarias y Forestales (IIAF) led by Dr. Carlos Antonio Martínez Palacios from the University of Michoacán at San Nicolas de Hidalgo—reveals the species’ potential as a source of products suitable for human and animal consumption. These include fillets, caviar (roe), protein concentrates, surimi (fish puree or slurry), aids in the preparation of animal fodder and dietary supplements for pigs and ruminants. In addition, plecos are a rich source of omega 3 fatty acids.
In view of its potential, Dr. Palacios—reported online on 9 September 2011 by Investigación y Desarrollo (www.invides.com.mx)—maintains that the fish is probably more of an angel than a demon. His team estimated there were 500 million tons of plecos in the Infiernillo Dam reservoir alone. Interestingly, in 2009, the figure quoted at the launch of a book of pleco recipes was around 40 million tons annually.
Despite the claim of potential benefit, however, the same team states it is “a high-impact invasive species with a high reproductive rate and a nesting behavior on river and lake banks that can cause landslides and flooding.” Nonetheless, studies are still under way to develop a fishery program that can exploit this new resource.
How “angelic” the reputation of this large suckermouth catfish remains, only time will tell.
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