California responders to invasive mussels may learn from
Midwest
While San Benito and California state officials grapple with the
consequences of the 1-3-year-old zebra mussels found recently in
the San Justo Reservoir, there are some lessons that can be learned
from communities around the Great Lakes.
California responders to invasive mussels may learn from Midwest
While San Benito and California state officials grapple with the consequences of the 1-3-year-old zebra mussels found recently in the San Justo Reservoir, there are some lessons that can be learned from communities around the Great Lakes.
Sheboygan County is one place along Lake Michigan that was especially hard hit by zebra mussels when they were first discovered in 1990 along the shores of Wisconsin. The zebra mussels, and more recently quagga mussels, another invasive species, have had a major economic impact on the region. It has hurt commercial farming, the tourism business and has had a devastating effect on the local ecosystem.
“The first thing you notice right away is for people that use it as a recreational area, is that first of all you have much more water clarity,” said Carmen Aguilar, an associate scientist with the Great Lakes WATER Institute, at the University of Wisconsin, Milwaukee. “Every particle in the water goes through them.”
The mussels, which can produce a million eggs a year, quickly remove the phytoplankton that many native species thrive on.
The second effect is that noxious bacteria start to thrive on the mussels’ waste.
“They create major slimes you might say,” said Wes Raddatz, a field supervisor Wisconsin Farm Bureau Federation for northeastern Wisconsin. “The wave action would break it lose and there would be all this gunk rolling onto the shores.”
When the mussels die, the sharp shells also end up on the shore and along the shallow bottoms.
“It’s not conducive to tourism and beachers,” Raddatz said. “[Tourism] brings in a great deal of revenue and there is agri-tourism – having people from Chicago or Milwaukee spend the day on the farm at a bed and breakfast and things to that aspect.”
Sheboygan County, Wisconsin may seem far removed from San Benito County, but the two share some similarities. Both host annual motorcycle rallies, both rely heavily on agriculture and are flirting with the idea of agri-tourism. In Sheboygan, agriculture accounted for $1.7 billion in economic activity in 2004, according to the University of Wisconsin Cooperative Extension. The top commodity is milk, but cattle, calves and crops make up about half the sales.
Since the announcement that zebra mussels were found in a reservoir that has been used to irrigate row crops in the San Juan Valley, locals have wondered what impact the mussels might have on the industry.
“We’re all kind of having a panic about it right now,” said County Supervisor Anthony Botelho, in an interview days after the presence of mussels was confirmed by state officials. “This is a huge problem. It plugs up irrigation systems… and on top of that, if that water is released you do have some possible drainage issues, and then we could even contaminate the Pajaro.”
At least in the Sheboygan area, the inland agricultural businesses have felt very little effect from the mussels.
“As far as inland, it hasn’t had any specific impact,” Raddatz said.
The U.S. Fish and Wildlife Services estimates that the mussels will have a $5 billion impact from 2000 to 2010 to U.S. and Canadian water users along the Great Lakes region. Much of the cost is due to maintenance of infrastructure since the mussels clog up pipes and intake valves.
“These mussels grow very quickly and cling to everything – plastic, metal,” Raddatz said. “One starts growing and next time there will be five. Next time there will be a big patch of them and everything is gunked up.”
Aguilar speculated that if handled well, the mussels would not spread from water used for irrigation in San Benito County. Understanding when the mussels are reproducing and when veligers – the second life stage when the larvae are forming the organ that they will eat and swim with – are present will be the key.
“If you know when they are reproducing – usually in September – know their cycle, you shouldn’t irrigate at that time,” Aguilar said.
Though San Benito has a network of creeks that connect to the Pajaro River and eventually flow into Monterey Bay, Aguilar said the mussels cannot survive long outside of water.
“If it is the little tiny ones, they can survive maybe a day,” Aguilar said. “When they are adults they can tolerate it being completely dry for a couple of days. They are animals – they eventually have to breathe.”
The Great Lakes region was hardest hit by the mussels because when they first showed up people didn’t understand how the mussels were spreading.
“By the time we figured out what was going on and how everything was coming from lake to lake,” Aguilar said, it was too late.
The zebra mussels live in shallow, warmer water and prefer rocky bottoms. The mussels are D-shaped with a flat bottom, Aguilar said, that attaches well to rocks and boats. When boats have water left in them and are transported by land to another body of water, if they have mussel eggs or veligers, they can easily invade the new body of water. It has been speculated that this is how mussels got into San Justo Reservoir, which is used by recreational boaters.
San Benito County Public Works has closed the reservoir to boaters until further notice.
“When there are so many boaters, we need to create a place they can switch the water,” Aguilar said. “We need to make it easy for them because people are not going to be careful. All it needs is one person who has veligers in the system to transport them to another place.”
The Great Lakes have set up procedures for commercial and recreational boaters to prevent the spread of zebra mussels to other bodies of water.
“We’ve been doing a pretty good job and people are taking care to prevent the spread,” Raddatz said. “And this isn’t the only invasive species they are concerned about.”
In the week after the mussels were discovered, the California Department of Fish and Game scheduled training in Sacramento and Fresno on proper inspection of boats to curb the spread of mussels.
It is unclear what impact the mussels will have on fish species in San Justo, but it is likely to decrease populations.
“In the Great Lakes we have a species of perch, yellow perch, and about the same time the zebra mussels began to flourish, the population was reducing drastically,” Raddatz said.
Scientists never specifically proved a connection between the decline in perch and increase in mussels, though it has been accepted by most people
“When you introduce something foreign into an ecosystem that has developed over a long period of time, you screw everything up,” Raddatz said.
Overall, Raddatz and Aguilar said Sheboygan residents have learned how to live with zebra mussels.
“People have adapted,” Raddatz said.
