Redd Count Surveys

Spawning Behavior of Trout and Utility of Redd Counts from Dr. Robert F. Carline

 

Redd Counts

            The primary motivation for initiation of the stream bank stabilization project was the poor reproduction of brown trout in the middle section of Spring Creek.  Spring Creek was divided into three sections: (1) the upper section extended from the Highway 45 bridge in Boalsburg to the Highway 26 (College Ave.) bridge in College Township; (2) the middle section extended from Highway 26 to the bridge on Rockview property just upstream of the outfall from their wastewater treatment plant; (3) the lower section extended from Rockview to Milesburg.

            Since Unit personnel first began redd counts in 1976, the total number has ranged from about 800 to almost 2,100.  Counts have varied among years and among sections.  In 1987 and 1988, we counted about 8 redds/km in the middle section.  In the upper and lower sections, we found 37 to 38 redds/km (Figure 1).  Not only were there fewer redds in the middle section, survival of trout embryos was about one-half that of embryos in the upper and lower sections.

            Redd counts were resumed in 1997, when most of the stream bank restoration work had been completed in the Cedar Run and Slab Cabin Run sub-basins.  In 1997 redd numbers in the middle section increased to 31/km, nearly a fourfold increase over the counts in 1987-1988.  Redd counts increased over the next three years and then fluctuated about the long-term mean of 46 redds/km, nearly six times higher than in 1987-1988.

            While we would like to credit this substantial increase in trout redds to our stream bank stabilization work, we need to be cautious about assigning cause and effect.  It is possible that there were decreases in sediment contributions from Slab Cabin Run downstream of our project boundary or from the borough of State College, where storm water drains into Thompson Run and then into Slab Cabin Run.  We do not know of any apparent reductions in sediment delivery to streams, but it may have occurred.  But clearly, the reduction in total suspended solids that was documented in Cedar Run and Slab Cabin Run translates to a reduction in sediment load of hundreds of tons.

Pictures From Redd Counts in 2015 and 2016

classbob and alcold