Rainbow trout (Salmo gairdneri) populations of the Great Lakes showed a great variability in timing of spawning migrations and life histories. This variability was examined to determine if rainbow trout populations of the Great Lakes are comprised of discrete stocks. Differences in timing of migration and spawning indicated that at least one spawning population may be distinctive and that others may be in progressive stages towards emergence of discrete stocks. The innate ability of this species to adapt to different environmental conditions, together with its ability to 'home,' provide rainbow trout in the Great Lakes with the potential to develop discrete stocks. The management of this species that allows for the development of this potential is emphasized.Key words: rainbow trout. Great Lakes, stocks, migrations, spawning, life histories, homing
The flow and turbulence characteristics of a new baffle–brush type fish pass were investigated experimentally in a 2 m wide rectangular flume with a bed slope of 4% and Reynolds and Froude numbers in the range 5 × 104–2·8 × 105 and 0·17–0·23, respectively. The baffle–brush fishway combines the properties of a baffle (Larinier) fish pass with the features of the brush-furnished fishway. The baffle–brush fish pass ensures continuous low- and high-velocity migration corridors for both strong (e.g. salmon) and weak swimming (e.g. river lamprey) fish, with negligible flow accelerations (i.e. quasi-uniform conditions). The turbulent kinetic energy (TKE) takes its maximum value near the centre of the baffle zone and decays towards the brush zone. The effects of the Reynolds number (Re) on the resultant velocity and TKE distributions were also investigated. For Re = 2 × 105, the TKE was in the range 0·05–0·21 m2/s2 with an average value of 0·11 m2/s2 in the baffle section, whereas it ranged between 0·007 and 0·04 m2/s2 with an average value of 0·02 m2/s2 in the brush section. In the proposed fish pass there is no need to build resting pools.
The flow characteristics (depth, velocity, energy dissipation) of a new baffle–brush fish pass were investigated experimentally in a 2 m wide rectangular flume which has a bed slope of 4% for discharges of 100–550 l/s. In all the experiments, quasi-uniform and sub-critical flow conditions and Froude numbers between 0·17 and 0·23 were observed. The Darcy–Weisbach friction factor was negatively correlated with the relative submergence of the brush elements. Two different characteristic velocity regions were identified, namely the baffle region and the brush region. The turbulence intensities were in the range 38–79% in the baffle zone and 13–31% in the brush zone. The hydraulic test results showed that this type of fish pass can produce adequate flow depth and favourable local flow velocities for the design discharge of 0·2 m2/s (relative submergence of brushes = 1·03), which is suitable for different fish species.
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