Effectiveness of Common Fish Screen Materials to Protect Lamprey Ammocoetes

Abstract

Understanding the effects of irrigation diversions on populations of Pacific lamprey Lampetra tridentata in the Columbia River basin is needed for their recovery. We tested the effectiveness of five common fish screen materials for excluding lamprey ammocoetes: interlock (IL), vertical bar (VB), perforated plate (PP), and 12‐gauge and 14‐gauge wire cloth (WC12) and (WC14). When fish (28–153 mm) were exposed for 60 min to screen panels perpendicular to an approach velocity of 12 cm/s in a recirculating flume, the percentage of ammocoetes entrained (i.e., passed through the screen) was 26% for the IL, 18% for the PP, 33% for the VB, 62% for the WC14, and 65% for the WC12 screens. For all screens, most fish were entrained within the first 15–20 min. Fish length significantly influenced entrainment, with the PP, VB, and IL screens preventing fish greater than 50–65 mm from entrainment and the WC14 and WC12 screens preventing entrainment of fish greater than 90–110 mm. Fish of all sizes repeatedly became impinged (i.e., contacting the screen for more than 1 s) on the screens, with the frequency of impingement events increasing during the first 5 min and becoming relatively stable thereafter. Impingement ranges were highest on the IL screen (36–62%), lowest on the WC14 and WC12 screens (13–31%), and intermediate on the PP and VB screens (23–54%). However, the WC14 and WC12 screens had fewer and larger fish remaining as time elapsed because so many were entrained. For all screen types, injuries were rare and minor, and no fish died after overnight posttest holding. Our results indicate that wire cloth screens should be replaced, where practical, with perforated plate, vertical bar, or interlocking bar screens to reduce lamprey entrainment at water diversions. Received October 26, 2011; accepted March 14, 2012

Effectiveness of common fish screen materials for protecting lamprey ammocoetes—Influence of sweeping velocities and decreasing flows

“…However, even with this improvement, lamprey ammocoetes still had higher rates of entrainment than juveniles of other species, including Chinook salmon (Oncorhynchus tshawytscha) (Swanson and others, 2004), bull trout (Salvelinus confluentus) (Zydlewski and Johnson, 2002), delta smelt (Hypomesus transpacificus) (Swanson and others, 2005), and Pacific lamprey eyed juveniles (Ostrand, 2007). This confirms the notion of Rose and Mesa (2012) that lamprey ammocoetes, particularly small ones (approximately <50 mm), are more vulnerable to entrainment than teleosts or larger lampreys.…”

“…We surmise that the comparatively low percentage of open area for PP resulted in higher focal velocities passing through the individual screen openings, resulting in a concomitant rise in impingements for fish of all sizes. We concur with Rose and Mesa (2012) that impingements are probably not harmful to young lampreys under most circumstances. We never saw any obvious injuries on our fish and survival was high.…”

“…Water temperature during normal rearing ranged from 5.0 to 8.5 °C and increased by 2-3 °C during some days when fish were fed with the inflow water off. Fish were fed a slurry of active yeast and commercial fry food (Gemma Wean 0.1; Skretting, Vancouver, British Columbia) using methods modified from Rose and Mesa (2012).…”

“…However, these tests were simplistic and probably a worst-case scenario for lamprey ammocoetes because they used small pieces of vertically-oriented screen material positioned perpendicular to the flow without a bypass route or a sweeping velocity (SV, the velocity of water flowing parallel to the screen surface). For this work, we increased the ecological realism of the tests done by Rose and Mesa (2012) to further explore the potential effects of irrigation diversion screens on ammocoetes. We designed and built a large, recirculating flume that could hold a 2.5-m-wide screen panel at an angle to the flow which could be controlled up to a maximum of 10 ft 3 /s.…”

Behavior and potential threats to survival of migrating lamprey ammocoetes and macrophthalmia

“…Most (65%) of these very small fish were 220 easily entrained, as were 30% of the <50 mm Western brook lamprey. Laboratory studies of a variety of screen 221 materials revealed similar rates of impingement and entrainment for small Pacific lamprey ammocoetes; but no short 222 term mortality and low rates of injury (Rose and Mesa 2012). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 attach to substrate with their oral disc.…”