Twin Lake Carp Tracking
The first step in managing carp populations is understanding the size of the population, where they congregate, and how and where they move around.
Fish biologists use a technique called Mark and Recapture to estimate population size and biomass. Electrofishing gear is used to temporarily stun fish to the surface, where the carp are collected, measured, and weighed. A distinctive clip is made to a fin. This process is repeated, and note is made of previously-marked fish that were recaptured as well as new fish that had not previously been captured. A mathematical formula is used to translate this mark and recapture data into an estimate of the carp population. Mark and Recapture surveys were completed twice in September 2016 on all three basins of Twin Lake. One more survey will be completed in September 2017.
Preliminary Carp Population Estimate - New
Forty carp were tagged with small radio transmitters implanted under their skin in Fall 2016. Commission staff periodically are out on the lakes with portable tracking antennas to track where the fish go. We are especially interested in finding out where they overwinter, and if they are in groups that would be easily harvested. The lake system is tributary to Shingle Creek through Ryan Lake and Ryan Creek, and we know there is a large population of carp in Shingle Creek, especially upstream in shallow Palmer Lake in Brooklyn Center. Carp are strong and wily swimmers and are known to swim miles through storm sewers and small channels. It is possible they are migrating between Twin Lake and Shingle Creek. As part of the project a stationary antenna will be placed on Ryan Creek, which is the outlet of the Twin Lake system into Ryan Lake. That stationary antenna will log every time a tagged carp swims past.
If the population estimate finds that the carp population is too large to sustain without negatively impacting water quality, then harvesting carp can help improve water quality and clarity in the lakes. The carp tracking will identify locations where they congregate, and commercial fishermen will harvest enough fish to bring them down to a manageable level. That harvesting would likely be in early 2018.
If the carp tracking finds that the fish are moving into and out of the lake system, harvesting won't have long-lasting benefits because the population will just move back in. The carp management project includes installation of fish barriers at key locations to prevent this from happening. Potential locations include the France Avenue weir in Robbinsdale, and two culverts under County Road 10 on the north end of Upper Twin. These culverts lead to wetland complexes north of CR 10 that could also be potential spawning locations.
Tracking Results - NEW May 2017
Over the winter months there have been significant changes in the location of carp within the lakes. As expected carp were located in large dense schools in deeper water habitats in the dead of winter (January). As conditions began to warm and watershed runoff began to move water under the ice (February), the carp were located in moderate depth areas in the lake and/or areas where storm water inputs were likely bringing in warmer oxygenated waters.
The March and April sampling efforts were a week apart and showed large changes in the locations of carp. In general, the carp appeared to be schooling in shallow waters and were likely preparing for spring spawning. Successful recruitment and spawning likely occurs in shallow wetland habitats and/or storm water ponds. An early ice out and limited spring flooding from snow melt and spring rains have kept the carp within the chain of lakes, however, as the waters continue to warm and with spring rains the carp appear ready to move into their spawning habitats in the near future. Marked carp have been found in Ryan Lake, probably swept over the France Avenue weir during rain events. Marked carp are also being found in upstream wetlands, which may be spawning habitat. Tracking efforts are occurring more frequently to capture the timing and location of spring spawning migrations and locations.
We will continue to track the carp through early spring 2018.
October 2016 Tracking
December 2016 Tracking
January 2017 Tracking
February 2017 Tracking
March 2017 Tracking
April 4 2017 Tracking
April 12 2017 Tracking
April 24 2017 Tracking
May 4 2017 Tracking
May 15 2017 Tracking
January-April 2017 Tracking Comparison