2021 Stream Sampling Trends: A Banner Year for Trout
Despite the drought conditions and warm summer, 2021 was a banner year for trout in this part of Wisconsin in terms of overall trout abundance and natural reproduction. Numbers of all size classes were higher than the average over the last 10 years on most streams. However, the numbers of age-0 (young-of-year, fish hatched this spring) and age-1 fish (fish hatched the previous spring, spring 2020 in this case) were through the roof in many streams! This was encouraging to see during the course of our summer sampling as many anglers expressed concerns about the trout population in the Rush River and others following the major flood event in late June 2020. The Rush, in particular, was impressive as always producing higher than average numbers of all size classes of fish from young-of-year fish up to adults with abundances of over 7,000 fish per mile. We completed a comprehensive survey of the Rush River this summer and I will wait to give away those details at the spring KiapTUWish meeting. Brook trout abundances were also higher than average in most streams as well including in the Rush River which was great to see. We also captured a record number of tiger trout within our surveys this year as well. The stream with the highest densities of trout this year was Pine Creek with over 10,000 brown trout per mile! Most of the fish here were either part of the age-0 (2-5 inches) or age-1 year class which is made up of fish in the 5-8 inch range. This was the theme for many streams, meaning that fishing will be very good in the next 1-3 years as these fish mature. Many factors may influence the survival of eggs/fry to the juvenile stage but one of the more influential factors is the timing of spring flood events. Flood events at the late egg stage or soon after fry have emerged will likely result in a very poor year class of trout. For example on the Kinnickinnic River, the graphs below show the large flood events in the early spring of 2019 and the steady low flows of 2021 which resulted in very poor year classes of trout in 2019 and very strong year classes of trout in 2021 according to our sampling (keep an eye on the vertical y-axis and the difference of the cfs between the graphs). The timing of these flood events can be a predictor of the strength of the year class of trout and how good the fishing may be in years to come.
-Kasey Yallaly
