Asian carp reproducing in Lake Erie basin.
Windsor Star, October 30, 2013.
For the first time in the Great Lakes, scientists have discovered that a type of Asian carp has successfully spawned in the Sandusky River in Ohio.
The study of grass carp published in the Journal of Great Lakes Research this month suggests other dreaded species — bighead and silver carp — will also be able to spawn in rivers connected to Lake Erie, said lead author Duane Chapman, a fish biologist with the U.S. Geological Survey.
The study also suggests that the grass carp population may be ready to explode, Chapman said.
“If they reach some point where they go through a rapid population increase then we’re going to have problems,” he said Monday from Missouri.
The study found that four grass carp caught in 2012 from the Sandusky River were hatched there, not released, and that they would also be able to reproduce. Tests done on bones using a laser in Windsor allowed scientists to conclude the carp, which were more than a year old, had lived in the Sandusky River all their lives and had not escaped from a pond.
Grass carp were introduced into the United States in the 1960s to control vegetation and they and other Asian carp escaped into the Mississippi River basin. The U.S. has an electric barrier in a Chicago canal to try to keep the invasive fish from reaching Lake Michigan. Some infertile grass carp are legally used in ponds to control vegetation.
Grass carp in large numbers would devour aquatic plants and hurt fish populations in Lake Erie, including yellow perch and northern pike that need plants as nursery habitat, Chapman said. They could decrease the number of ducks and geese that need vegetation for food and cause other damage such as increased shoreline erosion, he said.
“We will see effects of grass carp if they become abundant much quicker than we would bighead or silver carp because the areas they’re going to impact are much, much smaller,” he said.
Grass carp have been in Lake Erie for at least 30 years but are rare, he said. There is usually a long lag between when a species is introduced and problems. “We don’t know for sure but they could easily be entering a period in which their population begins to grow exponentially.”
There are four species of Asian carp: bighead, grass, silver and black carp and the fear is they will have catastrophic consequences if they get into and reproduce in the Great Lakes. They are large fish; in the case of grass carp they can grow to 100 pounds and live more than 25 years.
Scientists used a laser machine at the Great Lakes Institute for Environmental Research at the University of Windsor to study a six-millimetre bone, called an otolith, in a fish head. Chemicals in the tiny otolith stay there, so the laser helped scientists to find a naturally occurring chemical called strontium in the bone. That showed the carp had grown up in the Sandusky River, which is unique with a high strontium to calcium ratio, Chapman said.
“This is all really CSI stuff,” he said.
U.S. scientists have two more fertile grass carp caught in 2012 in the Sandusky River to analyze. Two grass carp caught on the Canadian side of Lake Erie in the Grand River in the last year were sterile.
MPP Toby Barrett (PC — Haldimand-Norfolk), who raised the issued of Asian carp in the Ontario legislature Monday, said the government needs to reallocate money to the Ministry of Natural Resources to work with the United States to keep Asian carp from establishing in the Great Lakes.
“Take action. We can’t be sitting up here in Queens Park debating yet another piece of environmental legislation that’s kind of feel good and looks good on the six o’clock news. We have a pending disaster here,” Barrett said Monday in an interview.