Completing population estimates to manage carp
On the heels of our recent announcement that common carp populations are under control in the Riley Chain of Lakes, MAISRC researchers continued their carp research and management efforts – this time in partnership with the Minnehaha Creek Watershed District on a 2.5-year project to study carp in the Six Mile Creek subwatershed. Researchers are taking the knowledge they gained from their work at Riley and applying it to a much larger and more complex watershed system.
The project, which is led by MAISRC research fellow Justine Koch and junior scientist Reid Swanson under the direction of Dr. Peter Sorensen, is a comprehensive assessment of common carp in the Six Mile Creek subwatershed. Their goal is to determine the distribution, abundance, movement patterns, and recruitment patterns of common carp throughout the area. This is the first step in an effort to understand how to sustainably manage common carp throughout the Six Mile Creek chain of lakes.
During the first full field season, electrofishing surveys revealed incredibly high estimates of common carp density and biomass. In an effort to validate these estimates, MAISRC partnered with commercial fisherman to recapture the carp that they had previously tagged in order to inform population data. Researchers had radio-tagged 30 carp in the Mud-Parley Lake system and tagged an additional 212 carp with small, plastic external tags called T-Bar tags.
When researchers set out to seine for the fish in mid-March, they were able to detect 15 of the radio-tagged carp. Despite a few snags throughout the day – like the net getting caught on underwater branches – fishermen were still able to enclose ten of the radio-tagged carp, and a grand total of a whopping 6,209 common carp (over a quarter of the total common carp population)! Several dozen gamefish were inadvertently captured as well, but were released back to the lake unharmed.
Of the carp that were captured, 54 had been previously tagged, which allowed researchers to estimate the total population size at roughly 23,000 carp in Parley and Mud Lakes combined. Developing a sustainable, long-term carp management plan is vital for controlling this highly invasive fish. Common carp are so invasive due to their high fecundity, low mortality rates, resilience, and ability to exploit productive and degraded waters for reproduction. By uprooting plants and releasing nutrients from sediments, carp degrade water quality and waterfowl habitat. Thanks to the Minnehaha Creek Watershed District for their support of this project! Stay tuned for more updates throughout the summer.