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 will be completed at least twice in September 2016 on all three basins of Twin Lake.
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 at the France Avenue weir, which is the outlet of the Twin Lake system into Ryan Creek. 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.
During the October tracking, the fish were dispersed along the near shore of the lakes where food was still abundant. In December, the fish began to cluster, and during the January 2017 tracking were found only in the deeper areas of Upper and Middle Twin Lake, with none found in Lower Twin.
We will continue to track the carp through early spring 2018.
October 2016 Tracking
December 2016 Tracking
January 2017 Tracking