Asian Carp in the Great Lakes
There have been many invasions of foreign species into new territories. Asian carp may pose substantial environmental risk to the Great Lakes if they become established there, according to a bi-national Canadian and United States risk assessment released today. Bighead and silver carps -- two species of Asian carp -- pose an environmental risk to the Great Lakes within 20 years, with the risk increasing over time. Lakes Michigan, Huron and Erie face the highest risk relative to the other lakes. The new risk assessment report was led by the Department of Fisheries and Oceans Canada and included a team of scientists from Canada and the United States. Two U.S. Geological Survey scientists were among the co-authors of the report.
The Asian carp value as a food fish has caused it to be exported from its native China to more than 70 other countries, where it has invariably escaped or been intentionally released to the wild. Today, the bighead carp can be found in the wild in Europe, South America, and North America. It also has been introduced into most of the Indian subcontinent (India, Pakistan, and most Southeast Asian countries) and to lakes in western China to which it is not native. Bighead carp are not always considered undesirable, invasive species where they are introduced outside their native range, and they continue to be stocked in some water bodies to support commercial fisheries.
The new report examined the likelihood of the survival and establishment of Asian carp in the lakes. It relied on prevention measures under way through November 2010, and did not take into account extensive preventive actions implemented since that time. The authors also assessed the probable ecological consequences should the fish invade the Great Lakes.
"Ever since these non-native fish first escaped and began to breed prolifically in the rivers of the Midwest, the questions everyone has been asking are: 'Can a breeding population survive in the Great Lakes and would it be a significant problem if they did?’" said USGS Director Marcia McNutt. "Now we know the answers and unfortunately they are 'yes and yes.' This study will help scientists and resource managers in Canada and the U.S. determine how and where to redouble their efforts as they continue to prevent the establishment of these invasive fish."
The reason for the high risk of invasion is because portions of the Great Lakes offer sufficient food and habitat to enable these invasive fish to spawn, survive and spread, the report’s authors noted. They identified the most likely pathway for Asian carp to enter the Great Lakes is via the Chicago Area Waterway System.
The report suggests that the major ecological consequence resulting from the establishment and spread of Asian carp into the Great Lakes would likely be an overall decline in certain native fish species, including some commercially and recreationally important ones. Such declines could occur because Asian carp would compete with prey fish that primarily eat plankton. This could lead to reduced growth rates and declines in abundance of prey fish species, and thus predatory fish would also likely decline. Asian carp also reduce survival of open-water fish larvae -- like those of walleye and yellow perch -- most likely through competition for plankton or by preying on the larvae.
The new report, developed with input from resource managers, decision makers and researchers from federal, provincial and state agencies, and other groups, provides a science-based assessment of the risk these fish pose to the Great Lakes. By involving both Canadian and U.S. scientists, the report drew upon the wealth of Asian carp expertise in both countries. The report will allow managers to make informed decisions for management of Asian carp and for prevention of their spread.
Communities are attempting to contain the spread of the extremely invasive bighead carp. New York has banned the import and possession of live bighead carp, with the exception of New York City, where they still may be legally sold in live food markets (but they must be killed before they leave the premises). Possession of live bighead carp has been illegal in Illinois since 2005. Since February 2007, using bighead carp as fishing bait has been illegal in Missouri. In December 2010, the U.S. Congress banned the importation of bighead carp.
For further information see Carp.
Big Head image via Wikipedia.