Where Did the Wipers Go? Hybrid Striped Bass Emigration Downstream from Dams

Methods

Summary

Hybrid Striped Bass are typically stocked in Iowa as small fingerlings (about 2 inches long) in early summer. We will raise the fish to a larger size (about 6-7 inches) so they can be safely tagged with Passive Integrated Transponder (PIT) tags. The proposed budget will allow for the purchase of 3,000 PIT tags, which will be inserted into 3,000 Hybrid Striped Bass. All of these fish will be stocked this fall into Big Creek Lake, a popular fishing destination north of Des Moines in central Iowa. Big Creek Lake is a reservoir with a large spillway which flows into Saylorville Reservoir; before this project, fish often washed down the spillway into Saylorville and eventually even into the Des Moines River. These fish cannot move back upstream and are lost from the Big Creek Lake fishery.

A new physical barrier has been installed blocking the Big Creek Lake spillway. This barrier is intended to reduce fish "emigration" or movement out of the reservoir, thereby maintaining higher fish densities and better catch rates for anglers in Big Creek. The spillway has been outfitted with several tag readers, electronic assemblies that can detect a PIT tag as it goes by. The readers use a low-frequency radio signal to constantly "ping" the surrounding area, and any PIT tagged-fish in the area "ping" back their unique ID number. This way, we can identify every individual fish that goes over the spillway. We can also use portable readers during fish sampling (e.g., electrofishing or gill netting) to identify fish that are recaptured, allowing us to estimate survival rate, population density, and even growth rate. This infrastructure has all been put in place as part of an ongoing Walleye research project.