Friday December 17, 2010

These are not the typical electrofishing surroundings, but they are certainly interesting. Construction begins this winter on a new fish-screened pumping plant for Tehama-Colusa Canal Authority, and to facilitate the construction they are building cofferdams in the Sacramento River just upstream of the Red Bluff Diversion Dam. A cofferdam is a temporary structure used to create a dry workspace within a watery environment, such as a river, lake or bay. This particular cofferdam is engineered from a series of sheet pilings hammered into the riverbed to form a reservoir 35 ft. wide and 300 ft. long. Once the area is isolated, the water is removed so that construction of the actual pumping plant can begin. However, due to the potential presence of several ESA-listed species, the fish need to be carefully relocated before all the water is drained (i.e. ‘fish removal’). That’s where we came in. In order to e-fish the isolated chamber, a crane lowered our electrofishing boat into the reservoir. (see photo above).
As water was pumped out of the reservoir we conducted multi-pass electrofishing. There are numerous challenges with working in this kind of environment, and we were well aware of the need to avoid touching the iron sheet piles with the anodes while sending current through the water. But we had not anticipated that the trickiest part of the whole sampling process was to avoid hitting our heads on the horizontal supports. Heads up!
Photos source: FISHBIO

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