Escapement Rate Research Articles

Modelling past migrations to determine efficient management rules favouring silver eel escapement from a large regulated Floodplain Lake

As human activities caused a dramatic decline of European eel population since the 1970 s, the European Union has set targets to ensure a 40% escapement to the sea of the silver eel biomass by considerably reducing anthropogenic impact. Thus, human obstacles to fish migration like dams and hydropower plants should enable efficient management measures ensuring safe passage for eels during the migration. In order to provide a quick and efficient assessment of eel conservation measure applied to the sluice gates of a large floodplain lake, we implemented a novel evaluation method using predictions on past migration seasons when no management measure were applied. For this purpose, we collected acoustic telemetry monitoring data over three migration seasons and fitted a predictive model based on Boosted Regression Trees (BRTs) to describe the influence of environmental parameters on migration. The water level difference over two days proved to be decisive, along with early migration occasions in the season, as an increase of at least 10 cm water level was associated with a sharp increase of migration probability. We then used the BRT model to predict migration occasions at the dam over 8 past seasons and forecast the impact on escapement of management measures if they had been applied. Thanks to this original prospective assessment of dam management measures, we identified an enhanced opening decision rule, capable of increasing the eel escapement for each year of the study. The management measure is particularly efficient during the years with poor hydrological conditions (i.e. droughts), that is the periods with the lowest initial escapement rates. Finally, efficient management measures to increase silver eel escapement were based on increasing the number of gate opening days by only a few days per year (c.a. 15%). However, the management measure only focused on silver eel migration, so that further investigations should consider the impacts of other threats occurring during the life cycle. This study also provides a highly operational approach for fast evaluation of conservation measures, avoiding lengthy and expensive monitoring campaigns of classical ex-post assessments.

Evaluating Chinook salmon (Oncorhynchus tshawytscha) response to artificial light in support of bycatch mitigation

In commercial trawl fisheries in the North Pacific and US West Coast, fishermen and scientists are evaluating if artificial lights facilitate escapement of bycaught Chinook salmon (Oncorhynchus tshawytscha) from the trawl by attracting them to an opening provided by a bycatch reduction device. Inconsistent behaviour and escapement rates when lights were used in the trawl led us to conduct a laboratory study to evaluate the role of light properties (intensity, colour, and strobe) on marine Chinook salmon behaviour. Results from this study suggest a negative phototactic response. Light colour and strobe, and the interaction between them, differentially affected behavioural response with regard to mean swimming speed and distance from and habituation to the light. White light intensity had limited influence on response; however, the range of trialed intensities was limited. While behaviour is contextual and responses in a laboratory setting cannot be directly extrapolated to responses in fishing gear, this study highlights the significant role of light properties when trying to affect behaviour for bycatch mitigation and the importance of distinguishing between a response to light and to illuminated surroundings.

Migration behaviour of Atlantic salmon smolts (Salmo salar L.) in a short and highly fragmented gravel‐bed river stretch

AbstractThe succession of migration barriers and different turbine types during downstream migration impede Atlantic salmon (Salmo salar L.) smolts from reaching the sea in time but is poorly studied. We investigated the isolated and cumulative impacts of 14 consecutive migration barriers (MBs) on downstream migration of 200 radio‐tagged smolts over an 18.9 km stretch of gravel‐bed river, by equipping five MBs with automated radio listening stations. At the level of isolated barriers, median research times (i.e. time between the first and the last detection upstream of a MB) varied between 0.1 and 0.7 h. The median crossing delays (i.e. time between the first detection upstream and the first detection downstream of a MB) varied between 1 and 2.9 h. Considering successive MBs, median cumulative crossing delays varied between 2.6 and 32.1 h and increased with the number of MBs. We observed a global mortality rate between 33% and 76%, increasing with the distance travelled and the associated number of MBs. Only 48% of the migrating smolts reached the end of the studied river stretch. Results suggest that the dynamics of the smolt downstream migration over this short highly fragmented stretch had a significant effect in terms of delays, mortalities and seaward escapement rate.

Trying to choose the less bad route: Individual migratory behaviour of Atlantic salmon smolts (Salmo salar L.) approaching a bifurcation between a hydropower station and a navigation canal

Contrary to small- and medium-sized rivers, little attention has been paid to the downstream migration of Atlantic salmon smolts in large-sized rivers and the size-related impact of hydropower stations. From 2014 to 2016, we investigated the downstream migration of n = 72 acoustic-tagged smolts in the Meuse river at a bifurcation zone between a hydropower station equipped with three Kaplan turbines and a navigation canal. A hydrodynamic model that solves the depth-integrated shallow water equations on a Cartesian grid using a finite volume technique was used to infer the influence of water discharge and flow velocity on the smolts' behaviour upstream of the hydroelectric complex. Of the migrating smolts, 41.5% performed back and forth movements before approaching the complex for the first time, sometimes over long distances and at a slow pace, leading to significant delays (3–298 h). Beyond about 250 m3 s−1, the water flow direction changes towards the hydropower station with a gradual acceleration. A median water discharge of 161 m3 s−1 and associated median flow velocity of 0.14 m s−1 tended to favour a more direct and downstream movement towards the hydropower station. On the other hand, the navigation canal was mainly approached at low water discharge (median 132 m3 s−1), due to a higher flow velocity (median 0.11 m s−1) at the entrance. Of the released smolts, only 38.6% passed through the complex, of which 36.4% migrated by the navigation canal and 63.6% by the hydropower station, with a median research time of 04:44. Among all the released individuals, the escapement rate at the end of the study site was 2.9% by the canal and 8.3% by the Meuse river. This site, which offers two non-optimal, unattractive and unsafe migration routes, turns out to be problematic for successful downstream smolt migration.

Evaluating the role of bycatch reduction device design and fish behavior on Pacific salmon (Oncorhynchus spp.) escapement rates from a pelagic trawl

Pacific salmon (Oncorhynchus spp.) bycatch is a significant driver in the management of walleye pollock (Gadus chalcogrammus) pelagic trawl fisheries in the North Pacific. Various bycatch reduction devices that permit salmon to escape from the trawl (‘excluders’) have been developed. High variability in escapement rates from the excluders underscores a lack of understanding regarding mechanisms that promote escapement. We developed an excluder that provided a 360˚ open area for escapement during towing, turns, and haulback. We used computational fluid dynamics simulations and flume tank testing to expedite development by producing quantitative flow and net mensuration data, which reasonably predicted performance at full scale under commercial conditions. During at-sea trials, salmon escapement rates were high (mean 0.58 ± 0.18); however, more comprehensive testing is needed among salmon species and over a breadth of fishing conditions. Video footage revealed that salmon disproportionately escaped by swimming forward from aft of the excluder during haulback and turns. This highlights the importance of providing an open path to the escapement area during these periods. Retention of any salmon despite the expansive, easily accessible open area reflects the important role played by perception of the open area and motivation of salmon to escape at that point in the fishing process.

Escapement of Broodstock Chinook Salmon From Whitlock Bay Spawning Station, Lake Oahe, South Dakota

Feral spawning fall Chinook salmon (Oncorhynchus tshawytscha) in Lake Oahe, South Dakota, are captured using a fish ladder and catch raceway at Whitlock Bay Spawning Station. The number of salmon that escaped the catch raceway and descended the fish ladder prior to spawning was unknown. During October 2017, all salmon that ascended the fish ladder at the spawning station were tagged. Tagged males remained in the catch raceway. Tagged females were moved to other secure raceways and used to estimate tag retention. Of the 383 tagged males, 159 (41.5%) were initially designated as escaped from the catch raceway. Tag loss in the females was 3.9%. Thus, the estimated male salmon escapement rate from the catch raceway was 37.6%. Male salmon remained in the catch raceway for one-to-three days before escaping. The escapement rate decreased over the month-long spawn, with nearly 60% of the males going back down the fish ladder in the first week of October, compared to less than 20% escapement by the final week. Such high rates of escapement from the spawning station may be negatively impacting the spawning efficiencies. Possible solutions include re-engineering of the fish ladder or daily removal of the salmon in the catch raceway to other more secure locations at the spawning station.

Transient inconsistency between population density and fisheries yields without bycatch species extinction.

Recent studies have demonstrated the great advantages of marine reserves in solving bycatch problems by maintaining the persistence (i.e., avoid extinction) of endangered species without sacrificing the fisheries yields of target species. However, transient phenomena rather than equilibrium states of population dynamics still require further research. Here, with a simple and general model, the transient dynamics of the target fish species are investigated under management which minimizes extinction risk of the bycatch species. An interesting finding is that fisheries yields can strongly fluctuate even if population density both inside and outside marine reserve only slightly varies (or vice versa), leading to transient inconsistency between the population densities and fisheries yields. This finding suggests that population density dynamics of the target fish species cannot be used to predict the transient phenomena of fisheries yields (or vice versa) in fisheries management. However, the unpredictability can be receded as the sensitivity analyses show that a large marine reserve size and low escapement rate can shorten the transient duration.

Saving the European Eel: How Morphological Research Can Help in Effective Conservation Management.

The European eel (Anguilla anguilla) is a critically endangered species, whose recruitment stocks have declined to nearly 1% compared to the late 70s. An amalgam of factors is responsible for this, among them migration barriers, pollution, habitat loss, parasite infection, and overfishing. A lot of recent studies focus on aspects that can increase the mature silver eel escapement rate, such as identifying migration barriers and developing passageways or addressing the impact of pollution on the eel's health. However, little attention is given to the eel's morphology in function of management measures. Worryingly, less than 50% of the currently installed management plans reach their goals, strongly indicating that more information is needed about the eel's ecology and behavior. Functional morphological studies provide insights on how species perform behaviors crucial for survival, such as feeding and locomotion, but also in how environmental changes can affect or limit such behaviors. Consequently, functional morphology represents an important biotic component that should be taken into account when making conservation decisions. Hence, here, we provide an overview of studies on the eel's morphology that do not only demonstrate its relation with ecology and behavior, but also provide information for developing and installing proper and more specific management measures.

Using automated video analysis to study fish escapement through escape panels in active fishing gears: Application to the effect of net colour

Quantification of the escapement rate of unwanted fish through a selective device is usually based on catch comparison. This study proposes a new, time efficient method to automatically compare two selective devices by automated counting of fish escapements through each selective device based on video sequences. First, sea trials were conducted to record video sequences of fish escaping a white and black square mesh panel. Then, all of the underwater sequences were automatically analysed by a computer vision software for automated object detection and tracking. Finally, the algorithm was assessed using 150 min of video sequences analysed by humans. We observed that the variability in escapements rate between all the observers on reference video sequences could reach 5%. As the difference in escapements rate between the algorithm and the observers was lower than the variability between observers, the automated approach was validated. The software detected a significant difference in fish escapement rate according to the net colour in the camera field of view: 60% of all fish escaped through the white panel. Our results suggest that net colour influences the escape rates of fish. The colour of the selective device should therefore be investigated further with the aim of increasing their efficiency. Further development of the software could be done to identify species and size of the fish and assess the effectiveness of a selective device by species and size.

Performance of a large partial-depth guide wall to divert downstream migrating Atlantic salmon smolts at Tuilières dam, Dordogne River

From 2010 to 2016, an evaluation of the performance of a partial-depth guide wall associated with three surface bypasses to ensure the safe downstream migration of Atlantic salmon smolts was conducted at the Tuilières power plant on the Dordogne River in southwestern France. The objectives of this study, during which 603 smolts were monitored using radio telemetry, were (i) to determine their escapement rate (passage through routes other than turbines), (ii) to analyse their behaviour faced with the structure and (iii) to assess the permeability of the guide wall as a function of turbine and spilling flows. The rate of escapement through the surface bypass routes varied from approximately 15% to 85%. The turbine flow was the main factor influencing the guide wall efficiency. The contribution of secondary bypasses, while significant for low flows, decreased rapidly with the increase in turbine flows. The vast majority of fish arrived on the two downstream bays of the wall or directly in the area of the main bypass, with the guiding effect of the guide wall becoming less noticeable with the increase of turbine flow. A modification of the depth of the guide wall in 2014 slightly improved its efficiency (by 5–10%) for low turbine flows. Logistic regression models were used to describe the evolution of the efficiency of the facilty as a function of the turbine flow and the probability of direct passage under a bay as a function of average velocity under this bay.

Density-Dependent Escapement of Rusty Crayfish from Modified Minnow Traps with Varying Throat Configurations

Abstract Modified minnow traps are the most widely used gear for collecting tertiary burrowing crayfishes. The throats of modified minnow traps are often widened more than 60% to accommodate the capture of larger crayfish. However, widening this crucial chokepoint into the trap may facilitate easier escape of captured individuals, especially as density in the trap increases. Increased escapement rates may reduce catch rates and corresponding estimates of relative abundance and lower detection probability. Incorporating a design feature, that is, throat restriction, that allows entry of all sizes of crayfish while reducing escapement would be an improvement over current designs. Here, I present the results of a paired field and laboratory experiment comparing the effectiveness of modified minnow traps with a throat restriction (restricted) and without such a feature (unrestricted) under varying crayfish densities. I chose rusty crayfish Faxonius rusticus as a study organism because it is widespread and abundant in the Laurentian Great Lakes region and commonly the focus of research and removal efforts. Rusty crayfish capture and escapement were strongly influenced by throat design and crayfish densities. The field component demonstrated that both traps performed similarly under low-to-moderate densities; however, at high densities catch in unrestricted traps plateaued at approximately 50 crayfish/trap, while restricted traps kept accumulating catch up to 155 crayfish/trap. Laboratory trials demonstrated that escapement for both trap types was negligible at low density and slightly higher at medium density: 0.8% for restricted and 11.5% for unrestricted. However, at high density, escapement from restricted traps was 8.8 vs. 45.3% for unrestricted traps. Our findings suggest that inclusion of a throat restriction may increase catch of rusty crayfish by reducing escapement and may be of particular use in removal projects or when sampling in high-density populations.

The effect of artificial illumination on Chinook salmon behavior and their escapement out of a midwater trawl bycatch reduction device

The Pacific hake (Merluccius productus) midwater trawl fishery is the largest groundfish fishery off the U.S. West Coast by volume. Catches comprise mainly Pacific hake, however, bycatch of Chinook salmon (Oncorhynchus tshawytscha) can be an issue affecting the fishery as Endangered Species Act (ESA) listed Evolutionarily Significant Units represent a portion of the total Chinook salmon bycatch. We conducted two separate experiments evaluating the influence of artificial illumination on Chinook salmon behavior and their escapement out a bycatch reduction device (BRD) in a Pacific hake midwater trawl. In Experiment 1, we tested whether Chinook salmon could be attracted out specific escape windows of a BRD equipped with multiple escape windows using artificial illumination. In Experiment 2, we compared Chinook salmon escapement rates out of the BRD between tows conducted with and without artificial illumination to determine if illumination can enhance their escapement. Our results show that artificial illumination can influence where Chinook salmon exit out of the BRD, but also demonstrate that illumination can be used to enhance their escapement overall. As conservation of ESA-listed Chinook salmon is an ongoing management priority, our research contributes new information on how artificial illumination can minimize adverse interactions between the Pacific hake fishery and Chinook salmon.

Seasonal variability of ichthyoneuston assemblage on the continental shelf and slope of the Southwest Atlantic Ocean, Brazil (20°–23°S)

Many marine organisms spend the early life history stages in neuston domain. Although the importance of ichthyoneuston, few studies were developed in the Southwest Atlantic Ocean. Therefore, this study aimed to improve the knowledge on ichthyoneuston of the Brazilian coast analyzing the vertical stratification and horizontal distribution of these organisms. Neuston samples were collected in daylight between 20°S and 23°S from February to April 2009 (late summer/early autumn; rainy season) and from August to September 2009 (late winter/early spring; dry season). Eggs of six taxa were identified: Anguilliformes, Engraulidae, Clupeidae, Synodontidae, Trichiuridae, and Maurolicus stehmanni (Sternoptychidae). The neustonic larval fish assemblage was composed by 40 families and 63 species. Mullidae and Myctophidae larvae were the most abundant in the rainy period while Mullidae and Mugilidae dominated in the dry season. Seasonal and spatial variation of larval fish assemblages in the neuston were structured by oceanographic features. The larval fish abundance on the outer slope stations may have been favored by the advection of an anticyclone that encompassed most of the study region during the cruise periods. In the rainy season, salinity and local depth structured the larval fish assemblage in a cross-shelf gradient, while in the dry season the larval assemblage was structured around temperature and north-south gradient. In the dry season, the cross-shelf gradient was less pronounced mainly because of the low abundance and frequency of mesopelagic larvae. The low frequency and abundance of some species are probably related to the net avoidance of fish larvae during the day or dial vertical migration, as many species migrate to deeper layers during the day and ascend to neuston only at night. Nevertheless, the present study presented baseline information about the seasonal and spatial variation of the neustonic larval fish assemblage influenced by the oceanographic conditions in the Campos Basin. We recommend to additionally collect night samples to decrease larval escapement rates and to compare night versus day catches to further investigate the influence of daily migration in the neustonic larval fish in the area.

Performance of Bycatch Reduction Devices in the Small-Scale Shrimp Trawl Fishery of the Persian Gulf

High rates of discards have been noted for shrimp fisheries worldwide and especially for the small-scale shrimp trawl fisheries of the Persian Gulf. Bycatch reduction devices (BRDs) can significantly decrease discards in shrimp trawl fisheries. We tested the performance of a square mesh panel BRD (SMP) and a juvenile and trash fish excluder device (JTED) in the small-scale shrimp trawl fishery of the Persian Gulf. Efficiency of the BRDs was determined in terms of shrimp loss, by-product loss, the reduction in discards by weight and differences in size selectivity of commercial fishes. Where a JTED was used, reductions in catch, by weight, were (mean ± 95% CI) 12% ± 2.35 for shrimp, 31.9% ± 5.22 for by-product fish and 49% ± 7.52 for discards. Similar reductions were observed when a SMP was used: 16% ± 4.19, 38.3% ± 6.41 and 45% ± 6.15 for shrimp, by-product and discards, respectively. There was no significant difference in the exclusion rate of discards between the JTED and SMP. Significant difference was found for loss of shrimp between JTED and SMP. The mean escapement rate for by-product species in trawl net with JTED and SMP were 35% and 40%, respectively. Selectivity curves of both BRDs indicated, that for each species, the length of 50% retention probability (L50) were smaller than the length at maturity (LM) and an increase in bar spacing in JTED and mesh opening in SMP would be required to delay capture until fish had reached Lm. The results indicated that SMP allows a higher proportion of sub-legal by-product species to escape the trawl, compared to the JTED used in the study. Implementing BRD requirements for the Persian Gulf small-scale shrimp fisheries would contribute to meeting strict sustainability criteria, a good outcome for this small-scale fishery.

The migration of stocked, trapped and transported, and wild female American silver eels through the Gulf of St. Lawrence

The stocking of juvenile eels and trap and transport programs of large yellow (American) eels (Anguilla rostrata) were initiated in Ontario to mitigate mortalities observed at hydroelectric dams and to increase escapement from the upper St. Lawrence River and Lake Ontario (Canada). A total of 380 migrating female silver eels (stocked, trapped and transported, and wild) were tagged with acoustic transmitters between 2011 and 2014. Their migration and escapement at the exit of the Gulf of St. Lawrence, the Cabot Strait, were recorded using acoustic receivers. Escapement rates varied between 8.9% and 20.0% annually (mean = 11.4%). A high proportion of stocked eels were detected (N = 27 of 43 detected at Cabot Strait), demonstrating their ability to escape the Gulf. No differences in migration speed or crossing locations at Cabot Strait were found among the three categories. Eels crossing Cabot Strait did not display diel and tidal patterns, but their estimated swimming depth indicated diel vertical migrations. The low escapement rates observed may be related to predation events and (or) the low and variable detection efficiency of the acoustic receivers’ line.

Silver eel downstream migration in the River Rhine, route choice, and its impacts on escapement: A 6-year telemetry study in a highly anthropized system

Several routes are available for the downstream migration of silver eels in the river Rhine system. Very different effects on migration success can result from this choice, such as speed and migration duration or escapement rate. We studied the downstream migration of silver eels in a river section with two different routes. The first route is the initial and old riverbed, with two dams equipped with two rather small or medium sized hydropower plants (HPPs) located at the beginning and at the exit of the bypass stretch. Both HPPs have small bar spacing (10 mm and 20 mm, respectively) and the second HPP has two downstream bypasses. The second route is a power canal, supplying four major HPPs (maximum discharge capacity = 1400 m3 s−1) and a nuclear power plant with cooling water. Firstly, this study focused on highlighting the factors influencing route choice. Secondly, we focused on the consequences of this choice. We demonstrate that water current management in the old riverbed at the study site had a 40% higher negative effect on eel survival than that by a consecutive passage in four turbines.

Behaviour, escapement and mortality of female European silver eels within a regulated lowland river draining into the Baltic Sea

AbstractMigration patterns of 146 female silver eels on their way through fresh and brackish water stretches of the Warnow River into the Baltic Sea were studied using acoustic telemetry. The majority of eels (77%) regained their expected downstream migration behaviour after a median rehabilitation time of 2 days. Positive rheotactic behaviour was observed for 23% of tagged eels after release, probably influenced by experimental procedures. The observed silver eel escapement rate was 63%. Two migratory groups were classified by significantly different migratory speed, time of residence in brackish waters and biometric silvering characteristics. Although the classification of silvering stages is based on these measures, the proportions of these stages did not reflect the observed differences in migratory behaviour. In the context of a permanent silver eel descent in the freshwater part of the Warnow River, a permanent escapement was likewise occurring into the Baltic Sea.

Comparison of Two Escapement Designs for Western Painted Turtles Captured in Modified Fyke Nets

AbstractAltering sampling methods to reduce bycatch during fish population sampling can introduce biases that affect the capture of target species. Therefore, understanding bycatch reduction devices and how they affect fish sampling is important. Our goal was to test two potential escapement designs intended to reduce bycatch of western painted turtles Chrysemys picta bellii during freshwater-fish population assessments with modified fyke nets. Design A tested an escapement flap on the interior of the modified fyke net and design B tested an escapement throat on the exterior of the modified fyke net. We completed 4-h and 24-h trials for turtle escapement to determine the effectiveness of each design for reducing turtle bycatch. We also simulated fish population assessments to determine the escapement of fish and turtles from each design. Turtles escaped from each design with mean escapement rates during the 4-h and 24-h trials of 71.1% and 63.8% from design A and 55.6% and 50.0% from design B, respectively. In the fish population assessment simulation we observed a mean escapement rate of 49% for turtles from design A, but a mean escapement rate of only 11% from design B. Species-specific escapement rates were observed for fish in both designs. Significant differences in the size structure of some species were observed. Escapement rates from design A were likely underestimated for most species captured due to movement of fish and turtles from the holding pen back into the fyke net. Based on our results, we do not recommend either design to reduce bycatch of turtles during fish community sampling without substantial refinement of the designs. Further research is needed to identify alternative methods for reducing turtle bycatch mortality.

Comparison of a rigid grid to a square-mesh panel in size selection for commercial fishing in the Persian Gulf shrimp trawl fishery

Two bycatch reduction devices (BRDs): a juvenile and trash fish excluder device (JTED) and a square-mesh panel (SMP), were tested in the Persian Gulf shrimp fishery from a small-scale shrimp trawler in October–November 2012. Each device was alternatively tested by using a small-mesh cover net to retain individuals that escaped the BRDs. Three valuable fish species—tigertooth croaker (Otolithes ruber), silver pomfret (Pampus argenteus) and silver sillago (Sillago sihama)—were selected for detailed analyses. Average escapement rates by number for commercial species in the trawl nets with either JTED or SMP were calculated as 24% and 33%, respectively. There were significant differences in escapement rates for Otolithes ruber and Sillago sihama between JTED and SMP (p < .05). In both BRDs, Pampus argenteus had the smallest escapement rate. A two-sample Kolmogorov–Smirnov test detected a significant difference (p < .05) in the length-frequency of Sillago sihama, and Otolithes ruber captured in the codend and cover net equipped with JTED. Selectivity curves of both BRDs indicated that for each species, the length of 50% retention probability (L50) was substantially smaller than the length at maturity (Lm), except for Otolithes ruber. From an ecological perspective, the codend equipped with SMP was superior to the codend equipped with JTED because it retained substantially fewer under-sized fish and had the smallest selection range. It therefore seems that replacing the standard codend with a codend equipped with SMP provides the best outcome for the fishery whereby fishermen will increase their catches of larger fish while simultaneously reducing their under-sized fish catches.

Effectiveness of pulsed direct current at reducing walleye escapement from a simulated reservoir

Fish escapement from reservoirs is problematic and makes management of these fisheries challenging. Historically, physical barriers have been used to limit fish movement but are prone to clogging and require constant maintenance. Thus, evaluations of alternative technologies are needed to limit reservoir fish escapement. Electrical barriers may offer an effective option for reducing fish escapement, but their effectiveness may be species-specific. Here, we predicted pulsed direct current with a graduated field would (1) alter walleye Sander vitreus behavior, (2) reduce escapement and (3) not induce mortality. Laboratory experiments compared walleye behavior, escapement, and mortality at four pulse (0, 0.3, 0.5, and 0.8ms) and three voltage (0, 60, and 80V) settings. The average voltage gradient 80cm in front of the outlet was 0.09V/cm (power density=1.36μW/cm3) at 60V and 0.14V/cm (power density=3.36μW/cm3) at 80V. Our results demonstrate that pulsed direct current was successful at reducing approaches and increasing deflections of walleyes, suggesting fish avoided the barrier. Altered behavior resulted in nearly an 80% reduction in escapement with smaller fish more likely to escape compared to larger individuals. However, pulse width and voltage did not influence escapement rates. Walleye mortality was 0% for control trials, ranged from 0.5–5.7% with the current activated, and was greatest at the highest barrier setting (0.8ms, 80V). Our laboratory results indicate pulsed direct current may be effective at reducing fish escapement from reservoirs. Lower pulse and voltage settings should be used due to their ability to reduce escapement while inflicting minimal mortality compared to higher settings. Additional work should evaluate the success of electric barriers in reservoir field settings under a wider range of conditions and on additional species.