As the South Fork Boise is currently closed to fishing now is the time to dip into stacks where we can find out a thing or two about the general area where the South Fork flows. This installment is a geology tour. At Idaho State University they have lots of geology information posted on line, including the Guidebook to the Geology of Central and Southern Idaho. In that book is the chapter “Cretaceous and Tertiary Intrusive Rocks of South-Central Idaho,” which includes a tour of the South For Boise River canyon area.
This geology tour begins with the road approaching Anderson Ranch Dam and goes downstream to the Cow Creek bridge where you drive from the South Fork back to Highway 20. Included is a side trip from Cow Creek Bridge to Danskin Bridge.
A couple of notes. The zero point for the tour, shown as 0.0, is the intersection of Sun Valley Road and Main Street in Ketchum. So the tour approaches the South Fork Boise from the east. Secondly, the interval mileage is shown in parentheses. Here goes: Continue Reading…
The 2012 South Fork Boise River fishery population sampling by Idaho Fish and Game shows a continuing population size structure that has lots of small fish and large fish making up the raw sample, but few middle sized fish. And the numbers of medium sized fish are too small to explain the numbers of the larger fish. Below is the graph showing the 2012 population distribution by size in 2012 compared with 2009 and 2006:
Fish between 200 and 400 millimeters - roughly eight to sixteen inches in length, are Continue Reading…
For the year 2012 southforkboise.org salutes Whitefish Ed for his devotion to the South Fork Boise River fishery and his early work to call attention to the stranding of young of year trout when the river flows are abruptly reduced in late summer. Previous posts have reported the details here about the concern that changes in flows could be affecting survival of juvenile trout, and then the follow up study where anglers and agency biologists worked together to assess the effects. Information on the results of the work is forthcoming in 2013 but for now let’s tip the hat to Whitefish Ed who initially called attention to this concern and inspired others to get the ball rolling on a study.
Whitefish Ed gets instructions from IDFG biologist Art Butts during the stranding study on September 17, 2012
In addition to the population survey that Idaho Fish and Game conducts every three years on the South Fork Boise River, there is also an effort to track the status of trout fry in several locations along the South Fork Boise River.
In late October a small crew was led by Art Butts from Idaho Fish and Game along with volunteers from Boise Valley Fly Fishers and the Ted Trueblood Chapter of Trout Unlimited. They monitored trout fry in six locations spread a few miles apart.
A section of the river would be measured for a 33 meter transect. The photo at left shows a portion of the river right (we are looking upstream so it’s on your left in the photo) portion of the South Fork just upstream of the confluence with Rough Creek. This is just upstream of the slide area where a January 1996 landslide formed a backwater along the South Fork.
Since Art was the guy who knows what he is doing with electricity he manned the backpack electroshocking unit. The three volunteers handled the nets, and as fry would emerge from the river bottom they would be netted and put in the five-gallon bucket. The larger photo above shows the method.
The next step in the process was counting and measuring each of the trout that had been netted and put in the bucket.
Each trout was counted and measured with a ruler. Total numbers are each site were recorded as were the measurements of all the fry.
The age zero trout were then put in the second bucket (both buckets held water of course) so they could avoid double counting or losing track of the number of fish.
This process was repeated for a total of six different sites. The data collected at these sites match up with previous fry monitoring activities in years past.
Over time we hope to get a better sense of the juvenile fish populations in the South Fork Boise River and what issues they face with flow and habitat management along the river.
As lay people we were interested to see these fry are in very shallow water and for the most part on or in and among the interstices of the rocks on the bottom of the channel. And they were right along the bank or shoreline. In places where there was better brush cover along the bank there appeared to be more dense numbers of these little fish. The more open areas seemed to have fewer fish.
This website is the creation of fishing enthusiasts who have a conservation interest in the South Fork Boise. And we’re as interested as any in the fishing conditions. But the best information on fishing is to be found with local fly shops, businesses and message boards. Here’s a working list: