Quagga Mussel Population Found in Harbor
Photo credit: U.S. Geological Survey
In January, the U.S Environmental Protection Agency (EPA) announced that during 2005, they found one quagga mussel (Dreissena bugensis) in the Duluth Superior Harbor. Now it appears as if this invasive cousin to the zebra mussel is beginning to thrive.
“Looking back, we can say that the one quagga mussel was just the tip of the iceberg,” said Jack Kelly, branch chief of ecosystem assessment research at the EPA’s Mid-Continent Ecology Division Laboratory. “It wasn’t just an anomaly, we have confirmed that there are more quaggas and that they are more widespread than we would have guessed in 2005.”
Kelly said it’s also reasonable to assume that the quaggas are reproducing.
First seen in the Great Lakes in 1989, quagga mussels had not, until 2005, been found in the Duluth-Superior Harbor or elsewhere in Lake Superior.
Quaggas are bad news. The fan-shaped mussel, which is about the size of an adult’s thumbnail, is a filter feeder. Like zebra mussels, quaggas accumulate pollutants and pass them up the food chain. They can also harm fisheries by eating the food that native fish need to survive, and clogging water intakes. In the lower Great Lakes, especially lakes Michigan, Ontario, and Erie, quaggas have out-competed zebra mussels. Their recent expansion in Lake Huron coincides with a large decline in the fishery and other changes in the lake’s food web. This has people concerned.
“The potential is there for quaggas to be even more of a problem than zebra mussels, especially in the Duluth-Superior Harbor,” said Doug Jensen, Minnesota Sea Grant aquatic invasive species program coordinator.
Initial Discovery is Tale of Persistence
Although they didn’t realize it at the time, in September 2005, EPA researchers from the Mid-Continent Ecology lab in Duluth collected the single quagga mussel among 20,000 organisms taken from the harbor as part of a program designed for early detection and monitoring of invasive species in vulnerable areas. The EPA sent the organisms to Wilson Environmental Laboratories, Inc., in Duluth for
There, taxonomist Igor Grigorovich thought one of the mussels found in the Superior entry looked suspiciously like a quagga mussel from his native Ukraine. He sent photos to another scientist for confirmation, but that scientist thought it looked more like a zebra mussel. Undaunted, Grigorovich, in cooperation with the EPA researchers, sent the mussel to the Cincinnati EPA research lab, which was doing DNA analysis for the project. Late in 2006, the analysis came back positive that the mussel was indeed a quagga.
“We reported the 2005 findings at a workshop that involved a number of local experts, including Sea Grant staff,” said Kelly. “Their input helped us modify and expand our sampling techniques when we sampled again in 2006. The preliminary results just now coming in reveal more quagga mussels at a number of locations in the harbor.”
“Finding the quagga mussels is evidence that our early detection program works,” said George Gray, assistant administrator of the EPA’s Office of Research and Development. “Identifying new threats in the early stages enables our partners in Minnesota and Wisconsin to take the most appropriate action to minimize the effects of this troublesome invasive species.”
Sea Grant and the departments of natural resources in Minnesota and Wisconsin used the initial finding to remind boaters of the steps outlined in the Stop Aquatic Hitchhikers™ Campaign to take to ensure they don’t accidentally transport invasive species between waters:
- Remove vegetation, mud, and animals from the boat, motor, and trailer.
- Drain water from live wells, bait wells, bilge, and motor.
- Rinse the boat and trailer with hot water OR let them dry for five days.
A less formal monitoring process turned up another, more unusual, species on a water intake screen in Thunder Bay, Ontario.
One of two Chinese Mitten crabs found in Thunder Bay, Ontario. Photo credit: Ontario Ministry of Natural Resources
The Chinese Mitten Crab: A Hairy Delicacy
Two individual Chinese mitten crabs (Eriocheir sinensis) were found at different times since 2005 at the Ontario Hydro electrical plant in the bay during routine inspections done to make sure the screens aren’t blocked with fish or other debris.
“A male was found in December 2005, and a female was found in December 2006,” said Karen Schmidt, fisheries technician with the Ontario Ministry of Natural Resources Lake Superior Office in Thunder Bay.
This saltwater species, which grows to about the size of a person’s hand, is causing problems for commercial shrimp trawlers on the West Coast. Removing numerous crabs from shrimp nets is time-consuming and costly, and the crabs often damage or kill the catch. Although Chinese mitten crabs can live in fresh water they need salt water to reproduce. This has biologists breathing easier because the species is not likely to become invasive in Lake Superior if it can’t reproduce.
Chinese mitten crabs are a burrowing species native to the Yellow Sea in Korea and China. Hairiness is their distinguishing characteristic; they feature dense patches of dark hair (resembling mittens) on their claws. (However, it’s not actually hair, but “setae,” long bristles of chitin – the tough, horny protein that forms the crab’s shell.)
Unlike the contaminant-ridden (and not to mention small) quaggas, mitten crabs are good to eat. They are a famous delicacy in Shanghai cuisine and some areas of their native range have been overfished. In fact, it’s thought they were introduced illegally into the San Francisco Bay in 1992 as a human food source.
Purposeful introductions aside, it’s believed that both the crab and the quagga mussel were spread by ballast water discharge. Their larvae are tiny and can easily fit through ballast water screens.
“These findings show that introductions of non-native species are still a problem in Lake Superior. The rate of introductions has been increasing since 1970,” Jensen said.
Good News for a Change: Invader Disappears!
Minnesota Sea Grant-funded researcher, Donn Branstrator, recently documented the first evidence of a decrease in the range of the spiny waterflea in North America. Branstrator, an associate professor with the University of Minnesota Duluth’s Department of Biology, and his team studied sediment and water samples from 53 lakes in northeastern Minnesota and Ontario, Canada, for evidence of the invasive spiny waterflea. Although the species is spreading with the flow of water in the lakes along the international border, the researchers confirmed that the waterfleas are no longer present in Boulder Lake or Fish Lake near Duluth.
Branstrator suspects that the disappearance of waterfleas in the two lakes has to do with fish predation and the lack of new introductions due to public education efforts.
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By Marie Zhuikov