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Watchorn looks for mosquito larvae in a water sample from a pond located north of Sheridan on Wednesday. He was looking for trends in the number of larvae found in the water samples to help determine if minnows have an affect on the mosquito population.  The Sheridan Press | Justin SheelyWatchorn looks for mosquito larvae in a water sample from a pond located north of Sheridan on Wednesday. He was looking for trends in the number of larvae found in the water samples to help determine if minnows have an affect on the mosquito population. The Sheridan Press | Justin Sheely

Saving nature with nature

SHERIDAN — Birds, bugs and fish. The interaction of this trio of local animals is the focus of a new research study playing out in the Sheridan area.

The study focuses on sage grouse, mosquitoes and fathead minnows. The sage grouse, which has been a species of concern for state and federal wildlife managers for several years due to declining populations in some areas of its range, has proven to be particularly susceptible to West Nile Virus, which is carried by mosquitoes.

“It is a great threat to sage grouse survival in northeast Wyoming. It appears to have a 100 percent mortality rate,” said Ryan Watchorn, a graduate student from the University of Waterloo in Canada who is participating in the project.

“We have not witnessed any birds that could survive it,” he added. “It basically reduces survival rates and may lead to population declines in sage grouse. Some research suggests that some populations may be one bad year away from extirpation (localized extinction).”

To help control mosquito populations and reduce the threat of West Nile Virus, larvicides are often used. While effective, they can be costly to purchase and apply, and have to be reapplied annually or more often. In an effort to find a cheaper, longer-term solution to the problem, Watchorn and his graduate professor Dr. Brad Fedy devised a study to determine if a finned ally could be brought in to assist in mosquito control efforts.

Over the summer, Fedy and Watchorn have introduced thousands of fathead minnows into local ponds and reservoirs.

Watchorn said laboratory studies have shown the minnows to be very effective at consuming mosquito larvae. However, the study aims to determine whether those results can be duplicated in real life pond conditions.

“They have been shown in lab studies to do a great job eating mosquito larva,” he said. “We are taking that knowledge and asking how can we start to quantify this in the field.”

There are 15 ponds in the study, with seven of them serving as controls (non-treated ponds). Watchorn said he tried to group treated and untreated ponds together based on similar size, water quality, vegetation and other characteristics to make comparing the ponds as equitable as possible.

Watchorn put approximately 25,000 fathead minnows in the eight treatment ponds earlier this summer. To measure the amount of mosquito larvae in the ponds, he uses a 350 mL dip cup to collect water samples and search the sample for mosquito larvae, a tedious but vital component of the study.

He will then compare the amount of larvae found in ponds with the introduced minnows to the amount found in ponds without the minnows.

While finding that the minnows are effective in reducing mosquito larvae is the primary goal, equally important is whether or not the minnows can be self-sustaining and reproduce successfully each year in the ponds, reducing the need for continued and repeated stocking of more fish.

“They were given the nicknames ‘toughies’ and that is for good reason,” Watchorn said about why fathead minnows were chosen for the study.

“They can survive a wide variety of water quality conditions,” He added. “They can survive lower dissolved oxygen levels than most other species of fish could. Secondly, they are readily available from many aquaculture suppliers at a very reasonable price. This is a very affordable fish to stock your ponds with. We expect a big chunk of them to die this winter but hopefully they have laid enough eggs to carry on that population.”

“We are tackling the problem from the source,” he continued. “What we are doing is implementing a biological control to the problem rather than larvicides. It has a lot to offer for local ranchers and people who want to be able to control mosquito populations on their property without using a lot of larvicides.”

 

About

Christina Schmidt

Christina Schmidt has worked at The Sheridan Press since August 2012. She covers a variety of feature stories as well as stories related to local schools.

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