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Los Padres Dam Steelhead Migration Data Results

by Bob Garbarino

An interesting recent article from FISHBIO discussed a study performed by the National Marine Fisheries Services on the migration of steelhead from the Carmel River up into Los Padres Reservoir and and their return out of the reservoir and downstream toward the ocean.  The data obtained from the experiment supports the concept that fishways at dams dams present what they call ecological traps.  The article describes ecological traps:  “Animals expressing instinctual behaviors that put them at disadvantage in an altered environment is referred to as an ecological trap.”    The goal of the study was to determine the how many fish made it back out of the reservoir on their way out to the ocean.   There are two routes for the fish to make it out:  over the spillway (when there is enough water) and through a bypass.  Both adult and juvenile steelhead preferred the spillway by a significant margin and that very low percentage of  fish make it back down to an antenna 8.7 miles downstream.  The scientists concluded that the dam significantly impairs downstream passage and the fishway is creating an ecological trap.  I encourage you to read the full article….it’s not long and and is quite interesting.  FISHBIO has an office in Santa Cruz.