Lake poisoning debated
Forest Lake, Minn. (AP) The Minnesota DNR wrapped up the
chemical treatment of two small lakes near Forest Lake with a
plant-based, fish-killing poison earlier this week.
The treatment of Howard and Mud lakes by boat and helicopter
will kill thousands of fish, including carp and bullheads, which
the DNR wants to replace with northern pike and other game fish.
The DNR also says spraying with a mixture containing rotenone was
the best option to make the lakes attractive again to migrating
The helicopter treatment was completed Monday. A small amount of
water was treated by boat Tuesday to complete the project,
according to Bob Welsh, the DNR’s north-metro area wildlife
Ducks Unlimited and the Minnesota Waterfowl Association are
paying most of the $90,000 cost.
But some residents of the area were worried about long-term
effects of rotenone, which they say could be harmful to people.
The DNR recently won a long legal battle to conduct the
treatment and says those fears are unfounded. The DNR says the
chemical treatment has no long-term health risks.
Since the DNR first proposed poisoning the lakes in 1997 to
eliminate unwanted rough fish and improve water quality, Charles
Huver, Patti Yaritz and other lakes residents have fought the
“I think Howard Lake should be regarded as a resource instead of
a dumping ground for hazardous chemicals,” said Huver, an
environmental consultant and retired University of Minnesota
professor who has lived near the lakes for nearly 20 years.
He and Yaritz, who has lived along Howard Lake for nine years,
argue the approach is, at best, misguided.
They say that rotenone, a naturally occurring compound found in
the roots of some South American plants, includes hazardous
chemicals such as trimethyl benzene, xylene and cumene. Nontoxic
alternatives exist, such as reverse aeration and unlimited fishing
and netting of rough fish, they contend.
But the DNR says the spray contains only a small portion of
rotenone and cites the Health Department in saying there are no
long-term health risks.
“If you open the barrel and stick your head in, it would be very
bad for you,” Welsh said. “But when it’s used according to the
label and delivered to target the way it’s supposed to be, it
volatilizes, evaporates and breaks down.”
Rotenone has been used as a fish pesticide in hundreds of
Minnesota lakes since 1945 with relatively little controversy.
Welsh said the water quality in Knife Lake near Mora improved
markedly after the lake was treated in 1989, although the DNR was
later fined for improperly rinsing containers.
The compound is used as part of a strategy to eliminate fish
that harm the water quality of shallow lakes. Rough fish such as
carp typically invade a system, stir up the bottom and make the
water cloudy and eliminate or consume grasses that provide food for
“Chemical treatment is always the last resort but, in this case,
chemical treatment is the treatment that’s going to do the job,”
said Welsh, adding there’ll be no impact to other wildlife such as
By next year, Welsh said the water should clear, grasses and
wild rice should become thicker, and ducks and geese should become
more abundant. The agency expects the treatment to hold up for a
decade or more, when carp are projected to return to their current