Redd Survey Results on the AuSable South Branch Shows Significant Decline

On November 11 members of Mershon-Neumann Heritage Chapter, the Mason Griffith Founders Chapter, and Anglers of the Au Sable met to wade the South Branch of the AuSable to count the redds. This annual event, done simultaneously on the main and north branches, gives the DNR Fisheries an estimate of the female trout population, trends of fish sizes, identifies protective cover needs, and productive and non-productive river reaches.

Per a recent email from Howard Johnson, founder and chairperson for Cedars for the Au Sable, raw data from the 2023 survey shows a 30% reduction in the number of redds compared to 2022. This is the first time since the beginning of the annual survey on the south branch of the Au Sable that such a remarkable reduction in the number of redds has occurred.

Six of the eleven surveyed reaches had a reduction in the number of redds – and one half of these were substantial reductions compared to past averages. Three of the reaches remained the same compared to last year - while two reaches had an increase…one of the reaches in the lower section of the surveyed area had a substantial increase.

DNR Senior Fisheries Biologist for the Au Sable, Matt Klungle has reviewed this information and has plotted the reaches to determine trends. He has noticed that the lower river – closer to Smith Bridge, is providing a higher concentration of brown trout redds. However, there is no definite pattern at this point. Matt is very thankful for the data our volunteers provide in this ongoing study.

Conducting the survey on November 11th this year,10 days later than prior years, might mean the spawning season was past the peak; some of the redds were older and more difficult to see in the low light conditions and the darker water. The plan for next year is to complete the south branch redd survey earlier in November.

Raw data will now be collected by Steve Johnson and entered into his database. At that time, Steve determines redds per mile of river, which is the method he uses to adjust for inconsistencies of not always surveying the same reach each year.

Thanks go to the eighteen volunteers that surveyed the south branch and especially Group Leaders: Chris Abbott, Mike Schmitz, Boyd Dillon, Jeff Minnis, Don Albrecht, and Dave Fisher. And a special thanks to Terry Lyons for supervising the project for Howard Johnson.