Flow in nature-like fishway and its relation to fish behaviour

Experimental results on the nature-like fishway induced flow field and its relation to fish behaviour are presented. A rocky-ramp with 5% slope was built along a 8.9m x 0.9m x 0.6m laboratory flume, and acoustic Doppler velocity measurements were taken in a grid with 186 points for low, middle, and high discharges. The flow is characterized applying spatial and point analysis techniques. Point analysis consistently shows that the boulder to boulder distance is small enough to disrupt turbulent coherent structures. At boulder wakes no predominance of sweep and ejection events occur, evidencing a good resting place for fish migration. The nature-like rocky-ramp offers a diversity of flow conditions controlled by the boulders geometry that might allow a variety of fishes to develop their preferred paths characterized by flow properties with different magnitudes depending on the particular species. Obtained results compare well with similar ones reported for other standard fishways.