Mufeed Odeh

Effect of Water Acceleration on Downstream Migratory Behavior and Passage of Atlantic Salmon Smolts and Juvenile American Shad at Surface Bypasses

Abstract Behavior and passage rate of smolts of Atlantic salmon Salmo salar and juvenile American shad Alosa sapidissima were compared between a standard (sharp-crested) and a modified surface bypass weir that employs uniform flow velocity increase (1 m·s−1·m−1 of linear distance). Within the first 30 min after release, significantly more smolts passed the modified weir than the standard weir, but no differences in passage rate between weir types were noted for juvenile American shad. More Atlantic salmon smolts and juvenile American shad were passed by the modified weir in groups of two or more than were passed by the standard weir. Mean lengths of passed and nonpassed smolts were not significantly different between weir types, but American shad passed by the sharp-crested weir were significantly smaller than nonpassed fish. Most individuals of both species that passed the modified weir maintained positive rheotaxis and strong swimming throughout the length of the weir. In addition to acceleration, visua...

Response of Juvenile Rainbow Trout to Turbulence Produced by Prismatoidal Shapes

Abstract Water velocity is a common measure of habitat suitability for salmonids. It is often noted that salmonid focal positions occur in low-velocity areas adjacent to high-velocity ones. Such locations are associated with increased turbulence. Turbulence in the stream regions typically occupied by salmonids is produced by flow separation around large objects such as rocks or on the riverbed. Turbulence has also been shown to increase the energetic cost of swimming for salmonids. Despite the link between cover and turbulence, no measurements of turbulence at the focal positions of juvenile salmonids have been reported in the literature. We measured turbulence at the focal positions of juvenile rainbow trout Oncorhynchus mykiss in a laboratory flume and found that those focal positions were characterized by low turbulence levels across a range of average velocities. Fish occupied highly turbulent locations if excessive average velocities were present. Eddy size, measured as the autocorrelation function o...

Use of the Average and Fluctuating Velocity Components for Estimation of Volitional Rainbow Trout Density

Abstract The relationship between discharge and fish density in streams is commonly accepted to be curvilinear, progressing from low discharge and low fish density to a peak and then declining to high discharge and low fish density. Discharge is related to water velocity; in general, as discharge increases velocity increases. Habitat complexity is an important aspect of salmonid ecology; more complex habitats support higher fish densities. Habitat complexity also influences the flow of water through the process of flow separation and turbulence production. More complex habitats generally exhibit higher levels of turbulence even though both may have similar average velocities. We tested whether the physical link between habitat complexity and turbulence was correlated with fish density. Turbulent kinetic energy and average velocity for three different levels of discharge and habitat complexity were measured in a flume. Turbulent kinetic energy was found to predict fish density, whereas average velocity did...

Effect of Slope and Headpond on Passage of American Shad and Blueback Herring through Simple Denil and Deepened Alaska Steeppass Fishways

Abstract Passage and transit time of adult upstream-migrant American shad Alosa sapidissima and blueback herring A. aestivalis were investigated in standard Denil and Alaska steeppass fishways with variable slope and headpond under semicontrolled conditions. Percent of American shad passed per unit time (percent passage) increased with temperature, while time required to ascend from the fishway entrance to the exit (transit time) decreased with increasing temperature for both species. Increasing fishway slope decreased percent passage of American shad, regardless of fishway type. Higher fishway slope decreased percent passage of blueback herring in the steeppass fishway only. Low headpond enhanced percent passage of American shad in the Denil fishway, but decreased percent passage of American shad in the steeppass fishway. Headpond level had no effect on percent passage of blueback herring in either fishway. Because headpond level in the steeppass fishway affected percent passage of American shad but not ...

Comparative hydraulics of two fishery research circular tanks and recommendations for control of experimental bias

Abstract Hydraulic characteristics inside two research circular tanks (1.5-m and 1.2-m diameter) with the same volume of water were studied to understand how they might affect experimental bias by influencing the behavior and development of juvenile fish. Water velocities inside each tank were documented extensively and flow behavior studied. Surface inflow to the 1.5-m tank created a highly turbulent and aerated surface, and produced unevenly distributed velocities within the tank. A low-flow velocity, or “dead” zone, persisted just upstream of the surface inflow. A single submerged nozzle in the 1.2-m tank created uniform flow and did not cause undue turbulence or introduce air. Flow behavior in the 1.5-m tank is believed to have negatively affected the feeding behavior and physiological development of a group of juvenile fall chinook salmon, Oncorhynchus tshawytscha. A new inflow nozzle design provided comparable flow behavior regardless of tank size and water depth. Maintaining similar hydraulic conditions inside tanks used for various biological purposes, including fish research, would minimize experimental bias caused by differences in flow behavior. Other sources of experimental bias are discussed and recommendations given for reporting and control of experimental conditions in fishery research tank experiments.