The impact of intermediate‐head navigation locks on downstream fish passage

Navigation in inland waterways is increasingly important worldwide and so is inherently the construction and use of navigation locks. However, the impact of navigation locks on downstream migrating fish is rarely documented. In Belgium, the Albert Canal connecting the Meuse River to the Scheldt Estuary may offer migration opportunities for European eel (Anguilla anguilla) and Atlantic salmon (Salmo salar), two critically endangered species. During their downstream migration phase (respectively silver eels and salmon smolts), both species have to pass five intermediate‐head navigation locks before reaching the estuary. Previous research showed that silver eel escapement is largely unsuccessful and that eels are delayed extensively at the navigation lock complexes. To get a better understanding of the mechanisms behind these failures and delays, we tagged and released 62 silver eels and 44 salmon smolts in the vicinity of one navigation lock complex of the canal. This paper reports the mechanisms behind the previously perceived delay, the route choices to pass the complex, and the risks involved. Of the 65% tagged eels and 73% tagged smolts that succeeded to pass the complex, respectively, 20% and 41% needed more than one trial to pass the complex. Moreover, 52% of all trials were via intakes of the lock filling system, at least four smolts (17%) died after intake passing, and about 30% of both intake‐passing smolts and eels stopped migrating after passage. Therefore, intermediate‐head navigation locks are a potential threat to downstream migrating fish, which requires more research to fully investigate its impact.     

Using acoustic tracking of an anadromous lamprey in a heavily fragmented river to assess current and historic passage opportunities and prioritise remediation

Anthropogenic structures extensively fragment riverine systems, reducing longitudinal connectivity, inhibiting migration and leading to severe declines in many fish populations, especially for diadromous species. This study investigated the upstream spawning migration of anadromous river lamprey (Lampetra fluviatilis) in a heavily fragmented tributary of the Humber Estuary, the location of one of the largest UK river lamprey populations. Overall, this study quantified river lamprey migration, spawning habitat distribution and historic river levels to develop a novel empirical index to understand the impact of man-made barriers and prioritise their remediation. Passage at all weirs only occurred during episodic high river levels, often after prolonged delays with no lamprey passing below average levels for the time of year or utilising the fish pass at the first weir (T1) at the tidal limit. Barrier passage opportunities at the first four weirs were only possible for 30.3%, 38.7%, 52.1% and 6.7% of the migration period, but were lower and severely limited in 15 of the last 21 years. In addition, more lamprey (60%, n = 18) were last detected in reaches with no spawning habitat than in spawning habitat (40%, n = 12). Given the impassibility of, and lack of retreat from, T1 to other Humber tributaries, the River Trent is currently considered an ecological trap for a large proportion of lamprey that enter from the Humber Estuary. This passage should be urgently remediated, per the prioritisation index presented here, to aid river lamprey conservation, especially given their status as a designated feature of the Humber SAC.     

Performance of a Vertical‐Slot Fish Pass for the Sea Lamprey Petromyzon marinus L. and Habitat Recolonization

In 2011, a vertical‐slot fish pass was built at the Coimbra Açude‐Ponte dam (Mondego River, Portugal), approximately 45 km upstream from the river mouth. The performance of this infrastructure for sea lamprey passage was evaluated between 2011 and 2015 using several complementary methodologies, namely radio telemetry [conventional and electromyogram (EMG)], passive integrated transponder (PIT) telemetry and electrofishing surveys. During the study period, the electrofishing revealed a 29‐fold increase in the abundance of larval sea lamprey upstream of the fish pass. Of the 20 radio‐tagged individuals released downstream from the dam, 33% managed to find and successfully surpass the obstacle in less than 2 weeks, reaching the spawning areas located in the upstream stretch of the main river and in one important tributary. Fish pass efficiency was assessed with a PIT antenna installed in the last upstream pool and revealed a 31% efficiency, with differences between and within migratory seasons. Time of day and river flow significantly influenced the attraction efficiency of the fish pass, with lampreys negotiating it mainly during the night period and when discharge was below 50 m³ s^?1. Sea lampreys tagged with EMG transmitters took 3 h to negotiate the fish pass, during which high muscular effort was only registered during passage, or passage attempts, of the vertical slots. The use of complementary methodologies provided a comprehensive passage evaluation for sea lamprey, a species for which there is a considerable paucity of valuable data concerning behavioural, physiological and environmental influences on obstacle negotiation. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.     

Implications of tagging effects for interpreting the performance of sea lamprey traps in a large river

Abundance estimates can be crucial for managing species of economic concern. The accuracy of these estimates can depend on the methods used to track animals and to estimate abundance from tracking data. We tested experimentally if disparate estimates of trapping efficiency calculated for sea lamprey (Petromyzon marinus) in the St. Marys River near Sault Ste. Marie, Canada could be explained by effects related to the invasiveness and handling involved in tagging or the tag size used in the marking procedures. Trapping is used to gauge adult abundance, trapping efficiency, and success of a binational sea lamprey control program in the Laurentian Great Lakes, North America. Our experiment compared nightly catches of sea lamprey marked with external fin clips, surgically-implanted passive integrated transponder tags (PIT-only), and surgically-implanted PIT and acoustic tags (PIT+acoustic). We found no evidence that the probability of being trapped was affected by the added invasiveness and handling of internal tagging. Nightly recaptures of PIT-only tagged sea lamprey, relative to fin-clipped sea lamprey, were not different from expectations based on the numbers of individuals released from each treatment group. Conversely, there was evidence of effects related to tag size. Nightly recaptures of PIT+acoustic tagged sea lamprey, relative to PIT-only tagged sea lamprey, were lower than expected based on numbers of individuals released from each treatment group. Effects related to tag size partially explain the disparate estimates in trapping efficiency observed for sea lamprey.     

Fishway passage and post‐passage mortality of up‐river migrating sockeye salmon in the Seton River,British Columbia

Adult sockeye salmon (Oncorhynchus nerka) were studied to assess the consequences of a dam and vertical‐slot fishway on mortality during their spawning migration in the Seton–Anderson watershed, British Columbia, Canada. Since previous research suggests fishway passage may be difficult, our main hypothesis was that the dam and fishway have post‐passage consequences that affect subsequent behaviour and survival. Eighty‐seven sockeye were caught at the top of the fishway, implanted with an acoustic telemetry transmitter, non‐lethally biopsied to obtain a small blood sample and released either upstream or downstream of the dam. Indices of physiological stress (i.e. plasma cortisol, glucose, lactate and ions) indicated that fish were not stressed or exhausted after capture from the fishway, and were not unduly stressed by transportation to release sites or net‐pen holding. Of 59 fish released downstream of the dam, 14% did not reach the dam tailrace. Overall passage efficiency at the fishway was 80%. Mortality in two lakes upstream of the dam was greater in fish released downstream of the dam (27%) compared to fish released upstream of the dam (7%; p = 0.04) suggesting that dam passage has consequences that reduce subsequent survival. Cumulative mortality of fish released downstream of the dam (n = 55) resulted in only 49% survival to spawning areas, compared to 93% of fish released upstream of the dam (n = 28). Survival was significantly lower for females (40%) than for males (71%; p = 0.03), a finding that has implications for conservation because spawning success of sockeye salmon populations is governed primarily by females. Copyright © 2010 John Wiley & Sons, Ltd.     

The influence of discharge and temperature on the ability of upstream migrant adult river lamprey (Lampetra fluviatilis) to pass experimental overshot and undershot weirs

The efficiencies of fish passes specifically designed and constructed to facilitate the movement of a limited number of species and life‐stages past structural barriers are likely to decline as site‐specific conditions shift with a changing climate. There is a need to develop realistic fish passage criteria based on understanding swimming capability and behaviour of multiple species in relation to temperature and flow. The influence of temperature and discharge on behaviour and ability of groups of migrating adult river lamprey (Lampetra fluviatilis), a threatened species, to pass a small overshot or undershot weir at night was investigated using a large experimental flume. Lamprey approached the weirs less, and more often maintained station by using the oral disk to attach to structure, under high flows. Oral disk attachment was more commonly observed during tests employing the undershot weir. Upstream movement tended to be in close proximity to the channel walls and floor where, compared to the mid‐channel, velocities were generally lower and velocity vectors more likely to be in a direction other than the bulk flow. Upstream movement was positively related to temperature, and was higher for the overshot weir. Weir passage rate was higher for undershot than overshot weirs, and negatively related to the maximum velocity at the weir. Passage rate was low when maximum velocities at the weir exceeded 1.5 m s^?1, although some fish passed at c. 1.7 m s^?1. Passage efficiency, the number of weir passes as a percentage of the number of approaches, was also higher for the undershot weir, but was not affected by discharge because lamprey approached less frequently at high flows. This study provides fish passage criteria under realistic conditions for an infrequently studied anguilliform species of conservation concern and provides a methodological perspective by which to improve fishway suitability for a wider range of species subject to changing climate. Copyright © 2010 John Wiley & Sons, Ltd. This article was published online on March 3, 2010. An error was subsequently identified in the Article title. This notice is included in the online and print versions to indicate that both have been corrected [April 12, 2010].     

Downstream Swimming Behaviour of Catadromous and Potamodromous Fish Over Spillways

Flow characteristics associated with spillways are important to restore ecological connectivity because spillways can either constrain or offer safe routes for downstream passage of fish. We studied the hydrodynamics of flow and downstream movement behaviour of the catadromous European eel (Anguilla anguilla) and the potamodromous Iberian barbel (Luciobarbus bocagei) in spillways with upstream face inclinations of θ = 90° (standard) 45° and 30° (modified). The standard spillway was tested for two water depths (H = 32 and 42 cm). Modified spillways facilitated downstream passage and reduced delay times of passage of the European eel. Upstream of the 90° spillway, distinct recirculation areas were observed, and associated turbulence strongly hampered downstream passage of fish. Both species were found to avoid turbulence, but barbel displayed stronger avoidance for areas of rapid changes in flow velocity when comparing to eels. Overall, eels were faster in passing the spillway and had a higher downstream passage success (80%) than barbel (32%). Eels were predominantly thigmotactic in contrast to barbel, which showed limited contact with structures. The results suggest that modified spillways may enhance passage survival. Copyright © 2015 John Wiley & Sons, Ltd.     

Dam Operations Affect Route‐specific Passage and Survival of Juvenile Chinook Salmon at a Main‐stem Diversion dam

Diversion dams can negatively affect emigrating juvenile salmon populations because fish must pass through the impounded river created by the dam, negotiate a passage route at the dam and then emigrate through a riverine reach that has been affected by reduced river discharge. To quantify the effects of a main‐stem diversion dam on juvenile Chinook salmon in the Yakima River, Washington, USA, we used radio telemetry to understand how dam operations and river discharge in the 18‐km reach downstream of the dam affected route‐specific passage and survival. We found evidence of direct mortality associated with dam passage and indirect mortality associated with migration through the reach below the dam. Survival of fish passing over a surface spill gate (the west gate) was positively related to river discharge, and survival was similar for fish released below the dam, suggesting that passage via this route caused little additional mortality. However, survival of fish that passed under a sub‐surface spill gate (the east gate) was considerably lower than survival of fish released downstream of the dam, with the difference in survival decreasing as river discharge increased. The probability of fish passing the dam via three available routes was strongly influenced by dam operations, with passage through the juvenile fish bypass and the east gate increasing with discharge through those routes. By simulating daily passage and route‐specific survival, we show that variation in total survival is driven by river discharge and moderated by the proportion of fish passing through low‐survival or high‐survival passage routes. Copyright © 2016 John Wiley & Sons, Ltd.     

POTENTIAL IMPACTS OF SMALL‐SCALE HYDROELECTRIC POWER GENERATION ON DOWNSTREAM MOVING LAMPREYS

Small‐scale hydropower is developing rapidly in many countries in response to policies of encouraging renewable energy and reducing reliance on fossil fuels. This rapid increase in the construction of hydroelectric turbines provides a substantial risk to migrating biota, especially fish. Some turbines, such as the Archimedes screw design, are regarded as relatively friendly to fish but have not yet been assessed for their potential impacts on threatened lamprey species. To assess the risk of impingement and the patterns of movement by emigrating river lamprey Lampetra fluviatilis transformers and drifting larval ammocoetes at the site of an Archimedes screw turbine in north‐east England, drift nets were set over the periods of January to June 2009 and November 2009 to May 2010. Drifting Lampetra sp. larvae were recorded in all sampling months, November to June, while emigrating lampreys were recorded in all months but June (93% captured between December and April), reflecting a higher period of impingement risk than expected. Night‐time catches were 24‐ and 8‐fold higher for transformers and larvae, respectively, than daytime catches. Catch per unit water volume data in different channel areas suggest that lamprey larvae behaved as passive particles within the river flow but that transformers selected areas of higher flow. Damage rates of lampreys passed through the screw were low (1.5%), suggesting minor impacts on downstream‐moving larval and juvenile lampreys. However, the cumulative potential impacts of multiple hydropower sites on downstream fish passage, including lampreys, should be considered by regulatory agencies when planning hydropower development within catchments. Copyright © 2012 John Wiley & Sons, Ltd.     

GUIDING OUT‐MIGRATING JUVENILE SEA LAMPREY (PETROMYZON MARINUS) WITH PULSED DIRECT CURRENT

Non‐physical stimuli can deter or guide fish without affecting water flow or navigation and therefore have been investigated to improve fish passage at anthropogenic barriers and to control movement of invasive fish. Upstream fish migration can be blocked or guided without physical structure by electrifying the water, but directional downstream fish guidance with electricity has received little attention. We tested two non‐uniform pulsed direct current electric systems, each having different electrode orientations (vertical versus horizontal), to determine their ability to guide out‐migrating juvenile sea lamprey (Petromyzon marinus) and rainbow trout (Oncorhynchus mykiss). Both systems guided significantly more juvenile sea lamprey to a specific location in our experimental raceway when activated than when deactivated, but guidance efficiency decreased at the highest water velocities tested. At the electric field setting that effectively guided sea lamprey, rainbow trout were guided by the vertical electrode system, but most were blocked by the horizontal electrode system. Additional research should characterize the response of other species to non‐uniform fields of pulsed DC and develop electrode configurations that guide fish over a range of water velocity. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

USING A NON‐PHYSICAL BEHAVIOURAL BARRIER TO ALTER MIGRATION ROUTING OF JUVENILE CHINOOK SALMON IN THE SACRAMENTO–SAN JOAQUIN RIVER DELTA

Anthropogenic alterations to river systems, such as irrigation and hydroelectric development, can negatively affect fish populations by reducing survival when fish are routed through potentially dangerous locations. Non‐physical barriers using behavioural stimuli are one means of guiding fish away from such locations without obstructing water flow. In the Sacramento–San Joaquin River Delta, we evaluated a bio‐acoustic fish fence (BAFF) composed of strobe lights, sound and a bubble curtain, which was intended to divert juvenile Chinook salmon (Oncorhynchus tshawytscha) away from Georgiana Slough, a low‐survival migration route that branches off the Sacramento River. To quantify fish response to the BAFF, we estimated individual entrainment probabilities from two‐dimensional movement paths of juvenile salmon implanted with acoustic transmitters. Overall, 7.7% of the fish were entrained into Georgiana Slough when the BAFF was on, and 22.3% were entrained when the BAFF was off, but a number of other factors influenced the performance of the BAFF. The effectiveness of the BAFF declined with increasing river discharge, likely because increased water velocities reduced the ability of fish to avoid being swept across the BAFF into Georgiana Slough. The BAFF reduced entrainment probability by up to 40 percentage points near the critical streakline, which defined the streamwise division of flow vectors entering each channel. However, the effect of the BAFF declined moving in either direction away from the critical streakline. Our study shows how fish behaviour and the environment interacted to influence the performance of a non‐physical behavioural barrier in an applied setting. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

A Practical Method for Obtaining Useful Quantities of Pheromones from Sea Lamprey and Other Fishes for Identification and Control

Pheromonally-mediated trapping is currently being developed for use in sea lamprey control in the Laurentian Great Lakes. To identify and test lamprey pheromones a practical procedure was needed to isolate relatively large quantities of pheromone from lamprey holding water. The present study developed such a technique. It employs Amberlite XAD7HP, an adsorbent resin which we found can extract over 80% of the sea lamprey migratory pheromone from larval holding water at low cost and with relative ease. This technique allowed us to collect tens of milligrams of all three components of the sea lamprey migratory pheromone, eventually permitting both identification and successful field testing. This technique might also be used to collect pheromones released by other species of fish.     

Consistent individual differences in sea lamprey (Petromyzon marinus) behaviour: Implications for control via trapping

We tested if consistent individual differences (CIDs) in the behaviour of sea lamprey (Petromyzon marinus) from the Laurentian Great Lakes could influence their vulnerability to trapping. The sea lamprey is invasive in the Upper Laurentian Great Lakes and the target of a binational control program. Trapping could be used for control if trapping efficiency is unbiased and effective. Our test involved comparing the behaviour of sea lamprey collected in the field from a trap (n = 42) at a barrier and electrofished (n = 9) downstream of the barrier. We quantified each individual's latency to exit an enclosure (a measure of exploration), proportion of time spent moving (a measure of general activity), and change in activity in response to a putative predator cue (a measure of boldness). CIDs were detected for each behaviour measured (intraclass correlations: 0.3–0.5). CIDs in behaviour also differed between trapped individuals and those collected downstream using electrofishing, irrespective of size, sex, and maturity status. Trapped individuals decreased their activity in response to a putative predator cue, while individuals collected using electrofishing increased their activity in response to the cue. Trapped individuals also tended to spend a greater proportion of time moving than individuals sampled downstream of the trap. However, the two samples of lamprey did not differ significantly in time taken to exit an enclosure. The behavioural differences between sea lamprey sampled from a trap and those sampled downstream of the trap suggest that CIDs in behaviour can influence an individual's vulnerability to trapping.     

Mortality of silver eels migrating through different types of hydropower turbines in Lithuania

Hydropower plants (HPP) are considered to be one of the major threats to the survival of European eels when they migrate downstream along inland water bodies during the early part of their annual journey to the spawning area in the Sargasso Sea. There are 98 HPPs in Lithuania and thousands throughout Europe. Numerous studies describe HPP induced mortality rates among European eels as variable depending on local, environmental, and technical factors. This heterogeneity in effect complicates theoretical extrapolation to eel mortality arising from specific types of HPP, necessary for effective management of local stocks. Silver eel mortality was estimated for 4 different HPPs in Lithuania. Mortality was estimated using RFID (Radio Frequency Identification, passive integrated transponders) tags and acoustic telemetry in a large HPP (>100 MW) with Kaplan turbines, a small HPP (<1 MW) with a Kaplan turbine and a fish passage, and for the first time in two small HPPs (<1 MW) with CINK turbines. The results supported a hypothesis that the mortality rate of migrating eels depends mainly on the type and size of the turbine. HPP induced mortality varied from 100% in a small CINK turbine down to 25% in the large HPP with Kaplan turbines. The importance of simple mitigation measures was highlighted by 34% of all tagged eels bypassing one of the HPP via an adjacent fish passage constructed for upstream migration of salmonids. The observed differences in mortality provide essential information for long term strategies designed to restore depleted eel populations in Lithuania and other European countries.     

Fishway passage success for migratory rainbow smelt Osmerus mordax is not dictated by behavioural type

Recent research has demonstrated that an individual's behavioural decisions can have a profound impact on an animal's fitness. For anadromous fishes requiring access to spawning habitat above obstructions, successful passage at fishways may at least in part be a function of an individual's behavioural type. The objectives of this study were to determine whether distinct behavioural types—bold and shy—could be distinguished within a population of anadromous rainbow smelt (Osmerus mordax) and, if so, whether passage success at a nature‐like fishway varied relative to behavioural type. Field‐caught rainbow smelt were tested for individual differences in boldness (i.e., willingness to engage in risk‐taking behaviour) using the metrics of exploratory behaviour, general activity, and response to a simulated predator. After testing, 276 rainbow smelt were implanted with a passive integrated transponder tag, released below the fishway, and their movements monitored via a stationary antenna array. The results of our behavioural assays indicated the presence of a behavioural syndrome among rainbow smelt, and that behaviour was partially repeatable. In total, 41.7% of fish entering the fishway passed successfully, but contrary to our initial prediction, boldness was not a significant predictor of successful passage. Instead, increasing water temperature and decreasing river discharge were consistent predictors of successful passage and greater distances moved through the fishway. Our findings indicate that the nature‐like fishway did not select for a particular behavioural type and that individuals representing the spectrum of bold–shy behavioural types could pass.     

The potential contribution of small coastal streams to the conservation of declining and threatened diadromous fishes,especially the European eel

Human‐generated pressures are continuing to have a detrimental effect on diadromous fishes, resulting in legislative initiatives to conserve and manage these species. Field studies to inform these initiatives focus almost exclusively on larger marine, estuarine, and inland waters, neglecting the role of small coastal streams and tributaries in population recovery. As an example of the potential contribution of very small coastal streams to diadromous fish recruitment, we report here on the densities and distribution of European eel Anguilla anguilla L. and flounder Platichthys flesus (L.) in one such stream, “La Warenne,” in northeast France in October 1998 and 1999. Both species were found mainly in downstream sites in both years—flounder were captured in low numbers only, but mean CPUE values for eel were similar to the highest densities reported in the ICES WGEEL database for larger rivers of Great Britain, France and Spain in the Interreg Atlantic and North Sea areas. This small dataset illustrates that small coastal streams may represent an important, but overlooked, role in conservation strategies for European eel, and possibly flounder, indicating the need for further field studies and investigations of existing data sources to evaluate the contributions to diadromous fish recruitment of these poorly studied water courses.     

Use of chemosensory cues as repellents for sea lamprey: Potential directions for population management

Sea lamprey invaded the Great Lakes in the early 20th century and caused an abrupt decline in the population densities of several native fish species. The integrated management of this invasive species is composed of chemical (lampricide) applications, low-head barrier dams, adult trapping and sterile male release. Recently, there has been an increased emphasis on the development of control methods alternative to lampricide applications. We propose as an alternative-control method the use of chemosensory cues as repellents for sea lamprey population management. Based on the available evidence at this time, we suggest that injury-released chemical alarm cues show promise as repellents for sea lamprey and further research should be directed at determining whether sea lamprey show an avoidance response to these types of chemosensory cues. From a management perspective, these chemosensory cues could be used to restrict sea lamprey access to spawning grounds. Repellents could also be used together with attractants like sex pheromones to manipulate sea lamprey behavior, similar to the “push–pull” strategies utilized with insect pests.     

Assessing migratory bottlenecks and escapement of silver eel (Anguilla anguilla) in the highly urbanized North Sea Canal basin,the Netherlands

Habitat fragmentation and migration barriers have attributed to the decline of European eel (Anguilla anguilla). The migration of silver eels through pumping stations, ship locks, and migration facilities within the North Sea Canal basin using acoustic telemetry and overall escapement by mark–recapture was studied. A network of 61 acoustic receivers and three PIT-tag stations was built, and 305 silver eels were tagged with acoustic transmitters and 3923 with PIT-tags. Of all the silver eels that were detected, 55% passed barriers between the polders and the canal and 46% also passed the barrier complex at IJmuiden to sea, mainly via the ship locks. Overall, silver eel escapement to the North Sea per year averaged 81,629 silver eels and 14.3% suffered mortality in the pumping station at IJmuiden. Migration speed was lower for silver eels that initiated their migration upstream compared with silver eels further downstream, higher for silver eels passing barriers later in the migration period, and highest at sea. This study of silver eel movement and escapement in the North Sea canal basin indicated several bottlenecks. Passage success along barriers varied strongly between sites and types of barriers. While at two smaller locations, silver eels migrated through the pedal valves in the ship lock gates, a small passage facility and the pedal valves in a ship lock at complex IJmuiden did not enhance silver eel migration. The barriers and unnatural canal system caused additional delay during silver eel migrations. Mitigation measures for management could include installing fish-friendly pumps, using pumping stations only during the day, and in addition opening ship locks and pedal valves at the beginning of the night.     

Performance of a prototype surface collector for juvenile salmonids at Bonneville Dam's first powerhouse on the Columbia River,Oregon

During April–July 2000, we radio‐tagged and released juvenile Chinook salmon (Oncorhynchus tshawytscha) and steelhead (Oncorhynchus mykiss) to evaluate a prototype surface flow bypass at Bonneville Dam on the Columbia River. The mock bypass, called a prototype surface collector (PSC), had six vertical slot entrances that were each 6 m wide and 12 m deep. The PSC was retrofitted to the upstream face of Bonneville Dam's First Powerhouse. Our objectives were to: (1) assess species‐specific differences in movement patterns and behaviour of fish within 6 m of the face of the PSC, (2) estimate the efficiency and effectiveness of the PSC and (3) evaluate factors affecting the performance of the PSC. We found that 60–72% of the fish, depending on species, detected within 6 m of the PSC entered it. Of the fish that passed the First Powerhouse at turbines 1–6, 79–83% entered the PSC. Diel period was a significant contributor to PSC performance for all species, and day of year was a significant contributor to PSC performance for subyearling Chinook salmon. The PSC was twice as effective (%fish/%flow) as the spillway, passing 2.5:1 steelhead and subyearling Chinook salmon and 2.4:1 yearling Chinook salmon per unit of water. If fully implemented, the PSC would increase the percentage of fish that pass the First Powerhouse through non‐turbine routes from 65–77% (without the PSC) to 76–85% (with the PSC), depending on species. Published in 2008 by John Wiley & Sons, Ltd.     

The behavioural response of migratory sea lamprey (Petromyzon marinus) to potential damage-released larval and migratory chemical alarm cues

We investigated the presence of damage-released alarm cues and the reactions they may cause in landlocked migratory sea lamprey (Petromyzon marinus) using semi-natural laboratory conditions during the day. In two separate experiments, migratory sea lampreys were exposed to stimuli prepared from the skinless carcasses and skin tissue of larval sea lamprey and from the skin tissue and muscle tissue of migratory sea lamprey. Migratory female sea lamprey swam significantly longer after being exposed to the stimulus prepared from the skinless carcass of larval sea lamprey. No significant changes were seen in the behaviour of the migratory female lamprey in response to larval skin extract or in the behaviour of male sea lamprey to any experimental extract in the larval extract experiment. In the second experiment that utilised migratory lamprey stimuli, neither male and nor female migratory sea lamprey showed a significant difference in their behavioural response among different treatments and controls. Our findings indicate that adult female sea lamprey respond strongly to damage-released alarm cues from larval sea lamprey; hence, the latter holds promise for sea lamprey behavioural manipulations for control purposes during the day. Further research is needed to examine responses to damage-released alarm cues at night, when migratory sea lampreys are more active.