By Graeme MacKay, Editorial Cartoonist, The Hamilton Spectator – Wednesday June 24, 2015
Invasive crab makes strange appearance in Cootes Paradise
Scientists at the Royal Botanical Gardens are scratching their heads about the bizarre discovery Monday of a live Asian crab, a creature listed as one of the 100 worst invasive species on Earth.
The adult crustacean — with its centre section, carapace, measuring 8 centimetres across — was identified as a Chinese Mitten Crab. It was inadvertently captured at the Cootes Paradise Fishway, a structure designed to keep carp out of Cootes Paradise from Hamilton Harbour, but allow other desirable species of fish to pass through.
“I was absolutely amazed how big the crab was and the fact that it was living in fresh water,” said Tys Theysmeyer, head of natural lands at the RBG.
According to the World Conservation Union, an international environmental group based in Switzerland, the burrowing crab with furry, mittenlike claws “modifies habitats by causing erosion due to its intensive burrowing activity and costs fisheries and aquaculture several hundreds of thousands of dollars per year by consuming bait and trapped fish as well as by damaging gear.”
But while the Chinese Mitten Crab has caused major problems in Europe, it is not viewed as a threat to the Great Lakes, says Hugh MacIsaac, an invasive species expert from the University of Windsor. The creature, he says, would not be able to reproduce.
The crab requires saltwater to bear offspring and that’s not something a crab in Hamilton Harbour could reasonably find. The St. Lawrence Seaway does not become salty enough until Quebec City, nearly 900 kilometres away from Hamilton.
In other parts of the world where fresh and salt water are closer together, such as the Thames River in England, it’s a different story. The crustacean is multiplying rapidly there, destroying fragile riverbanks as it preys on native species.
Six years ago, Londoners were told that the crab was safe to eat and to some it has become a food source. But high numbers continue.
There have been occasional discoveries of the crab in the Great Lakes over the years, but Monday’s was the first report in Hamilton Harbour. MacIsaac says the creature probably found its way to the harbour in the ballast water of a ship.
The crab was picked up by the Department of Fisheries and Oceans and was being analyzed. A spokesperson was not available for comment. (Source: Hamilton Spectator)