Piranhas Found in Michigan Waters.
Three large vegetarian piranhas with human-like teeth have been discovered in Michigan, amid growing concern among wildlife officials over tropical and invasive fish infiltrating the Great Lakes region. Over the past month, two red-bellied pacu piranhas have been caught in Lake St Clair and one other in the Port Huron area in Michigan. They were probably illegally dumped by people who didn’t want to keep them in their aquariums any longer. The tropical fish, imported from South America for home aquariums, prefers not to tear apart carcasses like other piranhas. Instead, it has square, blunt teeth that look much like human dentures, which it uses to nibble upon nuts and seeds.
The fish, which can measure more than 30in, are warm water creatures and are unlikely to survive in the colder environment of Michigan. But wildlife officials are grappling with a growing threat of an invasion of the Great Lakes by introduced fish species. “Pets released into the wild that survive can spread exotic diseases to native animals. In the worst-case scenario, released animals can thrive and reproduce, upsetting natural ecosystems to the degree that these former pets become invasive species,” said Nick Popoff, a manager at the Michigan department of natural resources.
Asian carp are considered the primary invasive species threat to the Great Lakes, which are a series of five large lakes that together make up the largest freshwater system in the world. Increasingly desperate measures are being taken to keep these newcomers out of the lakes – including the building of a “fish wall”. Authorities have constructed a 7.5ft wall near Fort Wayne, Indiana, in a bid to halt the onward advance of the Asian carp. The 2-mile-long earth berm, which replaced a temporary chain-link fence, is designed to stop the carp from swimming through Indiana’s rivers into the Great Lakes ecosystem. The US Army Corp of Engineers is currently working on a more sophisticated “lock and dam” system that would allow water to pass through but keep invasive species from swimming through. Asian carp were imported to the US in the 1970s to filter pond water in fish farms in Arkansas. Flooding allowed them to escape and spread northward. The species has no natural predators in the US and can gobble up 20% of its bodyweight in plankton each day. Some Asian carp grow to more than 100lbs and now represent the vast majority of biomass in the Illinois and Mississippi rivers.
Careless release of pets and unwitting introduction via international travel has brought a number of harmful species to the US. It’s feared that climate change will help expand the range of some invasive species, which can then out-compete native animals and disrupt ecosystems. Florida is often viewed as the frontline for invasive species in the US, with animals such as Burmese pythons, feral hogs and lion fish altering the ecology of the region. The state is now also home to the world’s largest rodent, according to biologist Elizabeth Congdon. There are around 50 capybaras loose in northern Florida, Congdon, of Bethune-Cookman University in Daytona Beach, told a recent conference in Missouri.
Credit: Oliver Milman for The Guardian (Abridged) 16 August 2016