Electrofishing the American River Featured

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Blocking Net
Monitoring in 2022 occurred in the first two weeks of September and Steve Schwartzbach participated as a volunteer from trout unlimited in the first day’s monitoring on the south Fork of the American River at 30 Milestone road. If you will recall, the first week of September was a week when a vast dome of high pressure settled over California producing record high daily temperatures. It seemed like a good day to be on a river, however ankle deep was not the best depth for working in hip waders

Fish species recovered during our first pass it seemed to me included primarily Rainbow trout, and Sacramento Suckers. While the complete results of the 2022 survey are not yet available we have the 2017 report results to compare. That report showed that the South Fork American below the project 184 diversion was the richest site in rainbow trout with 3,589 trout per mile estimated and 33.9 pounds of rainbow trout per surface acre. Data for other sites are as follows: Alder Creek (1,810 trout/mile and 74.6 lbs/SA), Silver Fork (1207,and 19.7) Pyramid Creek (1,479 and 6.5), Echo Creek (354 and 11.8) and last was Caples creek which had zero Rainbow Trout.

The El Dorado Irrigation District operates the El Dorado Hydroelectric Project (Project 184) which is licensed by the Federal Energy Regulatory Commission (FERC). This project comes with about 15,000 Acre feet of water rights for EID supplied by Echo Lake, Lake Aloha, Caples Lake and Silver Fork Lake. FERC requires the monitoring of Rainbow Trout populations in six streams reaches affected by the project. These waters include Lower Echo Creek, Lower Pyramid Creek, Caples Creek below Kirkwood, Silver Fork American River at Forgotten Flat, Lower Alder Creek, and South Fork American River below Carpenter Creek (access by 30 Milestone Tract).
EID was last licensed for the project in 2006. Monitoring is to occur in two successive years every 5 years. Monitoring has occurred in 2011 and 2012 and in 2016 and 2017.

Steve met the EID crew and a couple of the consultants at the Safeway parking lot in Pollock Pines to make introductions, sign liability waivers and coordinate vehicles. We then caravanned to 30 Milestone tract which is forest service land with a few recreational cabins right on the river.

When we arrived at the site there were already several trucks and crews present. With our additional arriving manpower, we had about 16 people. We needed them. The South Fork monitoring site is one of the most complicated of the waterbodies to survey. It consists of pool, riffle and run habitat, but the site is really two sites because at this location the river is divided by an island. On this day the flow of the river at our sampling site was at the fish flow minimum of 16 CFS, as some river water was actively being diverted upstream into the EID flume. Water depth varied from ankle to hip height, but was mostly below the knee. While there was some shade, most of the river sampling was done in full sun.

To compare results from site to site and from year to year electrofishing survey protocols require standardized efforts on standardized stretches. Two 100 meter stretches of river, one on each side of the island were isolated by block nets stretched across the river upstream and downstream. Four electroshockers were employed, 3 on the main stretch and one on the north stretch. The electroshock technique involves carrying a 40 pound pack with an anode tail and a cathode probe on a 6 foot rod. The shocker time is set to zero and seconds of use are recorded on each shocker to allow effort standardization later. The amount of current employed is adjustable as is the amount needed for effective shocking. It is desirable to use the least amount of current possible to minimize injuries to fish. The effectiveness of the current depends upon the conductance of the water. On this date our conductivity was about 60 uS/cm. (For reference – distilled water has a conductance of 1 and sea water a conductance of about 50,000). Conductivity is a measure of the amount of soluble ions in the water. If conductivity is low then adding salt blocks to the water is a good option and we did that. This minimizes the difference in conductivity between fish and water minimizing injury potential. We started at 300 Volts and ended up going to 375 volts, 25 volts at a time. Hip waders and rubber gloves must be used by all. Typically the shocker operator is followed by one or two net men and a bucket guy. The shock travels between the anode and cathode and it is best not to find yourself between these two, especially if your waders are leaking.

To effectively compare years and sites there are a number of formulas for standardizing effort. The effort involves usually at least three passes where a crew works upstream from the downstream net going back and forth across the stream shocking, netting and capturing in buckets. Captured fish are moved and stored upstream away from shocking in netted cages. After the 100 m stretch is completed fish are processed for size weight and species and returned to storage in live car cages in the river away from electroshocking. Two more passes are usually needed to effectively remove all fish from the sampled section. An algorithm on reduced effectiveness is used to calculate whether a fourth pass is needed, each time fish are being processed and data recorded between passes.

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