Laboratory Evaluations of Fine-mesh Traveling Screens – 5 Years of Research

Biological performance – primarily the 48-hour survival of collected larvae – was evaluated in the laboratory with fine-mesh traveling screens.  The first year of testing used small acrylic, tabletop, flumes to evaluate the effects of approach velocity, duration of impingement, and fish length on the survival of six species of freshwater fish.  These data were used to select variables for further evaluation with fully-operational fine-mesh traveling screens in a large flume.  In Years 2-4, survival of larvae was assessed with screens from three different manufacturers using 0.5 to 2.0 mm screen meshes.  Test variables included approach velocity (0.5 to 2.0 ft/s), duration of impingement (2 to 8 minutes), and fish length (5-28 mm) with eight species (bigmouth buffalo, bluegill, common carp, golden shiner, white sucker, channel catfish, hybrid striped bass, and rainbow smelt).  There was considerable variability in survival depending upon species, especially with the earliest life stages.  In general, smaller fish (<12 mm) had poor survival while larger fish (>12 mm) had good survival.  This increase in survival appears to coincide with development of scales and increased musculature.   In general, there was a trend toward decreasing survival as duration of impingement or velocity was increased, but these relationships were not always significant.  Duration of impingement was rarely a significant predictor of survival.  In a fifth year of testing, a screen that removes organisms directly from the screen panel with a fish-friendly pump was evaluated.  The variables tested included velocity (0.5 to 4.0 ft/s) and fish length (11-52 mm).  Fish species tested included: bigmouth buffalo, bluegill, common carp, and white sucker.  Survival with this screen exceeded 65% and for two species survival was greater than 89% for all conditions tested.  A similar pattern of increasing survival as fish grew larger was observed with this screen as with the previously tested screens.