Testing Adult Pacific Lamprey Performance at Structural Challenges in Fishways

Abstract

Adult Pacific lampreys Lampetra tridentata migrate through areas of difficult passage and high water velocity by attaching their oral discs to substrate and then releasing and bursting upstream. In fishways at dams, this burst‐and‐attach behavior can be ineffective, particularly where suitable attachment surfaces are unavailable. We used an experimental fishway to test performance of adult Pacific lampreys when confronted with a series of structural challenges. These included vertical steps near fishway weir orifices, squared versus rounded orifice entrances, and floor‐mounted metal grates. All experimental challenges simulated common existing structures in weir‐and‐orifice fishways at Columbia and Snake River dams. Most experiments were paired with field evaluations of radio‐tagged Pacific lampreys or video observations of untagged individuals in situ. Field and experimental results consistently indicated that the structural challenges reduced passage efficiency and lengthened passage times. Improving Pacific lamprey passage may be facilitated by removing or modifying vertical steps and other sharp‐edged corners and by providing adequate attachment surfaces. Such accommodations should be especially beneficial in areas with high water velocity. The findings demonstrate how fish morphology and behavior should be explicitly considered in the design or retrofitting of fish passage structures.

Extreme inefficiency of two conventional, technical fishways used by European river lamprey (Lampetra fluviatilis)

“…High efficiencies recorded at vertical slot fishways for lamprey can be partly attributed to the provision of passage routes near the sides and substrate of the fishway. The rounding of entrances, turns or bulkhead challenges in fishways should be considered, as this modification has demonstrably improved entry success, increased passage efficiency and decreased passage time for Pacific lamprey (Keefer et al, 2010;Moser et al, 2002b). For low to moderate gradient nature-like or rock-ramp fishways, high passage efficiencies for lamprey are likely to be achieved given their suitable oral disc attachment sites and heterogeneous flow conditions, whereby lamprey can exploit low velocity areas for refuge and passage.…”

“…Most research concerning lamprey passage has originated in North America: firstly, in detailing the efficacy of large fishway facilities at hydropower dams in the lower Columbia River for threatened Pacific lamprey Lampetra tridentata (Jackson and Moser, 2012;Johnson et al, 2012;Keefer et al, 2009Keefer et al, , 2010Keefer et al, , 2011Moser et al, 2002aMoser et al, , 2002bMoser et al, , 2011, and secondly in investigating the capabilities of the sea lamprey Petromyzon marinus, an invasive species in the Great Lakes, to negotiate barriers, in order to develop preventative measures to block their upstream migration (Hanson, 1978;Hunn and Youngs, 1980;Katopodis et al, 1994). However, differences in the size, swimming capabilities and behaviour of lamprey species and migratory forms warrant care in extrapolation between species.…”

Passage and Behavior of Radio-Tagged Adult Pacific Lampreys (Entosphenus tridentatus) at the Willamette Falls Project, Oregon

“…Moser et al (2002a,b) noted that sharp corners or floor grates reduced the passage efficiency of lampreys through fishways at Columbia River dams because they precluded consistent lamprey attachment. Modifications such as rounding corners and placing steel plates over some area of the floor grates improves lamprey passage (Moser et al 2005, Keefer et al 2010 and such measures should be implemented at the Project. Third, the possibility that delayed tagging effects might impact lamprey passage success at dams is real, but research in this area is sparse.…”

Network analyses reveal intra‐ and interspecific differences in behaviour when passing a complex migration obstacle

“…burst‐swimming speed), structural impediments and environmental factors may explain the low passage rates observed for Pacific lamprey at Columbia River dams compared to salmon (Keefer et al . , ; Johnson et al . ; Kirk et al .…”