New survey assesses global impact of invasive catfish

The Common Pleco, or “janitor fish” (Pterygoplichthys pardalis), is a popular species of catfish known for cleaning aquariums by eating their algae. It is also a member of one most successful invasive genera found in freshwaters. A recent survey in Zoological Studies by Orfinger and Goodding concludes that four species and one hybrid in the genus have successfully established themselves globally and, while they cause overall moderate damage to the environment and socioeconomics, they may be causing significant damage in some localities.

Just because a species is invasive does not necessarily mean it has a large negative impact. However, we do not know what kind of impact these catfish have because they have a complex taxonomic history and no comprehensive database to track all documented invasions and sightings.

Pterygoplichthys cf. disjunctivus captured by Alexander Orfinger in central Florida, USA, with its erect dorsal spines highlighting its "sailfin" namesake. Photo by Aileen Perilla.
Orfinger and Goodding made an impact assessment by searching through all the literature on the genus and using it to make a map of impacted areas. From there, they quantified local and global impacts using Generic Impact Scoring System (GISS), which addresses impacts on a sliding scale using multiple categories covering environmental to socioeconomic impacts (e.g., impacts on fishermen and - women).

One category is the impact due to hybridization, or different species or varieties mating to yield “hybrid” offspring. Hybrid forms can be less fit than both of their parents, more fit than one and less than the other, or more fit than both. “This last case of so-called ’hybrid vigor’ could potentially help invasive species flourish in their new ranges, but nobody really knows” said Alexander Orfinger of the University of Central Florida.

The study found that at least one Pterygoplichthys hybrid form successfully invaded nonnative waters, and there is debate as to whether the two most dominant invaders - P. disjunctivus and P. pardalis - are in fact hybrid forms themselves. “There has not been a lot of work done in this area, and Pterygoplichthys might present a good study system to tackle such questions."

How are these catfish so successful? "At the end of the day, the root of many exotic species originates in the pet trade,” said Mr. Orfinger. “Prospective pet owners need to do their due diligence in learning about their pets’ long-term needs. Otherwise, you end up with situations like Pterygoplichthys in which we have a physically large and resilient group of fishes invading fresh waters all over the world."

Read the full article, published by Zoological Studies, here

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Map of areas impacted by nonnative Pterygoplichthys spp. Different colors represent different species.

Guo A, Hao Y, Wang J, Zhao Q, Wang D. 2014. Concentrations of osmotically related constituents in plasma and urine of finless porpoise (Neophocaena asiaeorientalis): implications for osmoregulatory strategies for marine mammals living in freshwater. Zool Stud 53:10. doi:10.1186/1810-522X-53-10.

Media contact: Noah Last: