Swimming in Two-Vector Flows: Performance and Behavior of Juvenile Chinook Salmon near a Simulated Screened Water Diversion

Abstract

We used a large, annular flume equipped with a simulated fish screen to assess the swimming and behavioral responses of juvenile Chinook salmon Oncorhynchus tshawytscha to two‐vector flows typifying habitats near water diversions, where small fish may become entrained. Groups of 20 fish (4.4–7.9 cm long, at 12°C or 19°C) were tested for 2 h at one of nine experimental flow regimes derived from combinations of three (approach) velocities perpendicular to the screen and three (sweeping) velocities parallel to the screen and a (0‐cm/s) control during daytime (lighted) and nighttime (dark) conditions. In the high‐velocity (resultant vector) flow regimes, all fish swam at velocities comparable to the critical swimming velocities measured for similar‐sized conspecifics, suggesting that exposure to such flow conditions near a water diversion is energetically expensive. Although most fish exhibited strong positive rheotaxis, older (smolt‐size) fish acclimated to the warmer temperature exhibited higher rates of negative rheotaxis (particularly in the intermediate‐velocity flow regimes), a behavior consistent with downstream migration. Fish life stage (length), time of day (light level), and water velocity influenced swimming velocity; sweeping velocity, swimming velocity, and rheotaxis influenced screen passage velocity. Regardless of the flow regime, juvenile Chinook salmon contacted the screen most frequently at night, and nighttime contact rates were not affected by the velocity of either flow vector. During the daytime, screen contact rates were inversely related to sweeping velocity and independent of approach velocity. Injury rates were low and unrelated to either flow or screen contact rates, and survival rates were high (>99%) in these predator‐free experiments. Fish screen designs that minimize screen exposure duration (e.g., via reduced screen length or increased sweeping velocities) should optimally protect valuable juvenile Chinook salmon, a species that encounters multiple water diversions along many of its migratory paths to the ocean.

Field‐Based Evaluations of Horizontal Flat‐Plate Fish Screens, II: Testing of a Unique Off‐Stream Channel Device—the Farmers Screen

“…Rose et al (2008) evaluated ranges of sweeping (15-143 cm/s) and approach (1-8 cm/s) velocities that were similar to ours. Other studies evaluated various designs of vertically oriented screens and reported results similar to ours for juvenile splittail Pogonichthys macrolepidotus (mean length of about 6 cm; Danley et al 2002), bull trout (median length, 25 mm; Zydlewski and Johnson 2002), and juvenile Chinook salmon O. tshawytscha (4.4-7.9 cm; Swanson et al 2004). …”

Can behavioral fish-guidance devices protect juvenile Chinook salmon (Oncorhynchus tshawytscha) from entrainment into unscreened water-diversion pipes?

“…Decreasing water-diversion rates below 0.37 m 3 ·s -1 for 0.46 m diameter unscreened pipes can also substantially decrease entrainment risk. Fish screens have been installed at many large waterdiversion projects in California, are generally very effective at minimizing juvenile salmonid entrainment (Swanson et al 2004;Gale et al 2008;Walters et al 2012), and are required in California on all new or renovated water-diversion structures in salmoninhabited waters (California Department of Fish and Wildlife 1996). However, the costs of installation, required maintenance, and legal regulations can discourage owners of existing water diversions (that are not required to be screened) from installing new fish screens.…”

Distribution and movement of domestic rainbow trout, Oncorhynchus mykiss, during pulsed flows in the South Fork American River, California

“…The fish was then removed from the anesthetic solution, weighed, and measured for its standard length (SL). A health index was calculated for each fish based on its external body condition, using a modification of the injury index developed by Swanson et al (2004). Damage was rated from 1 (no damage) to 5 (severe damage) for the following 11 physical features: eyes, operculum, fins (anal, caudal, dorsal, pectoral, pelvic), scales, abrasions, fin blood, and presence of fungus.…”