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North Branch Wiscoy Creek Habitat Enhancement Evaluation (2013)

Technician holding 18 inch wild brown trout from N. Branch Wiscoy Creek.
Eighteen inch wild brown trout from
N. Branch Wiscoy Creek.

In July 2013, Region 9 fisheries staff and angler volunteers conducted trout population sampling on the North Branch Wiscoy Creek (N. Branch). This sampling was the 2nd year of post-habitat enhancement monitoring on the stream. Trout population sampling had been conducted in 2010 and 2011 prior to a habitat enhancement project and to compare with populations after completion of the project.

Habitat Enhancement Project

In July 2011, 57 "Lunker" structures (456 total feet) were installed along a 2,100 foot section of public fishing rights easements on the N. Branch (North Branch Wiscoy Creek Habitat Enhancement Project). This project was done to increase habitat for adult wild brown trout in this highly productive stream. Areas where the structures were installed were deepened to approximately 2 feet and the stream width was narrowed by 1/4 to 1/3. Prior to the work, this stream section was overly wide, shallow and overgrown with alder from past land use practices and held very few larger adult trout.

Post-Enhancement Assessment

Fisheries crew electrofishing N. Branch Wiscoy Creek.
Electrofishing sampling on the N.
Branch Wiscoy Creek.

Trout population sampling was done on the entire 2,100 foot habitat enhancement section (seven 300-foot sites) as well as one additional site on the N. Branch and one site on nearby Trout Brook to serve as "control sites." For all adult (yearling and older) wild brown trout, densities varied significantly at both the control sites and the habitat enhancement section from 2010-2013. Densities of brown trout >10", >12" and brown trout biomass declined from 2010-2013 at the two control sites. However, densities of brown trout >10", >12", >14", as well as brown trout biomass increased substantially in the habitat enhancement section from 2010 to 2013. It is expected that in future years we will see further increases in both overall adult trout density and density of larger wild brown trout in the habitat enhancement section as the trout population fully occupies the enhanced habitat.

Lunker Structures = Larger Trout

Angler fishing along lunker structures on North Branch Wiscoy Creek.
Angler fishing along lunkers on N.
Branch Wiscoy Creek.

A further indication of how effective the lunker structures were as habitat for yearling and older trout in general and larger trout in particular can be seen in Table 1 below. Of the 600 total yearling and older trout captured in the 2,100 foot long habitat enhancement section, 436 (73%) were found in the four 300-foot sections with lunkers and only 27% in the three 300-foot sections without lunkers. Even more impressive, 119 of the 132 fish >10" and all but two of the fish >12" and >14" were in the sections with lunkers.

The two largest brown trout captured in the habitat enhancement section in 2013 were 14.9" and 18.1" while in 2012 they were 17.0" and 18.0". In 2010 the two largest were 15.7" and 12.6" and in 2011 they were 13.9" and 12.6". The largest wild browns captured at the control sites on the N. Branch and Trout Brook were 13.2" and 15.6" respectively.

Table 1. Comparison of the number of yearling and older (adult) wild brown trout (# adult, # >10", # >12" and # >14") in each 300 foot reach sampled within the habitat enhancement section on N. Branch Wiscoy Creek in 2013.
Section Lunkers present Feet of Lunkers in site # adult brown trout # >10" # >12" # >14"
2100' - 1800' Y 168' 99 33 12 4
1800' - 1500' N 0 25 1 0 0
1500' - 1200' Y 72' 124 34 8 2
1200' - 900' N 0 56 3 1 0
900' - 600' Y 104' 89 26 5 1
600' - 300' N 0 83 9 1 0
300' - 0' Y 112' 124 26 9 1
Total - 2100' - 456' 600 132 36 8