Our services and technologies

ATET-Tech is an environmental consulting company focused on fish conservation at industrial water intakes including once-though-cooling, hydroelectric, irrigation, pulp & paper, and manufacturing.  This includes assessing wether a facility requires "fish protection or not" based on several facility and ecological based factors. ATET-Tech staff have considerable experience in impingement and entrainment monitoring as well as evaluation of different fish mitigation technologies. ATET-Tech has experience evaluating different fish protection systems especially related to cost-effectiveness, biofouling, and strengths/weaknesses in mitigation control. Technologies reviewed have included fish mitigation options such as acoustic and light systems, fish pumps, air bubble systems, fish return systems, fine mesh wedgewire screens, barrier nets, flow reduction methods and other approaches used at industrial plants.

ATET has also developed a new underwater LED device (Light Guidance Device, LGD) for fish management applications which has been designed to work alone or integrated with different fish-conservation methods listed above. The device can also be used for research applications.

Our unique technology is available for purchase or long term rental by interested groups such as industrial water users, consulting groups, environmental engineering and consulting groups and universities.

ATET also provides consulting services jointly with technical personnel from Carleton University, both in laboratory and field investigations using our systems. CanNorth, one of the largest environmental service providers in Western Canada will be available to conduct field studies using the LGD on hydropower projects.

For the field evaluation of LGD, we are also partnering with Milne Technologies to use remote sensing technologies such as acoustic cameras (ARIS-DIDSON),  imaging cameras (M3), and hydroacoustics.

In the United States, LimnoTech (Ann Arbor, Michigan) is a strategic partner and will conduct investigations at hydropower and other water user facilities.

Our LGD technology uses red, green and blue LED light modules capable of producing different color combinations flashing at frequencies of 1 to 40 times per seconds to address species specific responses of fish and other aquatic organisms. Different controlled spectral/frequency and intensity combinations are controlled by user friendly software which have been demonstrated to be effective at either attracting or repelling juvenile fish such as Largemouth Bass and White Sturgeon.

LGD technology can either be used alone or integrated with another system such as coarse physical barriers such as bar racks and louver systems.

We also provide unique technical advice for integrated systems based on our years of experience with fish protection systems.


In Canada, recent amendments to the fisheries protection provisions (FPP) of the Fisheries Act came into force. Under the amended Act, the Minister of Fisheries and Oceans has the authority to authorize a project that causes serious harm to fish (which by definition includes the death of fish) by taking certain factors into account. In the United States (US), the US Environmental Protection Agency (USEPA) requires generating facilities to meet fish impingement and entrainment reduction criteria under Clean Water Act (CWA) §316(b). There are several different compliance options for reducing fish impingement one of which includes a system of technologies which may include lights integrated with physical barriers.

One environmental challenge of small hydropower development relates to fish passage both upstream and downstream. Small scale hydro developments are often an impediment to these migrations. Efficient fish passage is required under many jurisdictions in order for regulating agencies to approve hydropower projects, whether they be new developments or under relicensing.

ATET-Tech has developed a novel Light Guidance Device (LGD) that allows for the generation of different frequencies of light, intensity and flash rate to be controlled by the user. This system works in conjunction with physical louvers interspaced strategically to maximize sufficient flow to run the hydroelectric power plant while minimizing the fish loss through the turbines. ATET-Tech is seeking patent protection for this new innovation and represents the competitive advantage of the company. This system would be installed in hydroelectric power plants to mitigate their impact to the fish populations.

The development of these technologies have been developed in collaboration with the National Research Council Canada Industrial Research Assistance Program (NSERC-IRAP), the Department of Fisheries and Oceans (DFO) and the Ontario Centre of Excellence (OCE).


An example of a fish diversion system using the lights with a reversed louver is shown in Figure 1. This example also shows a traditional bar rack which is angled to the flow. In this integrated system, lights are used for fish orientation to the structure as a possible attractant towards a bypass (it is also possible for repulsion frequencies to be used at specific locations behind the louver array to increase louver effectiveness). The addition of light devices may allow an increased louver spacing which reduces costs and biofouling concerns. In this application, the traditional bar racks would be replaced by a modified angled “reversed” bar rack or louver with light support devices. The design parameters of this system are unknown and may be species specific.

Figure 1. Example of integrated fish protection system with reversed bar racks and light system.



We propose to test the effectiveness of a new portable LED device (Light Guidance Device, LGD, ATET-Tech Inc.) that uses red, green and blue LED light modules capable of producing 16 million color combinations flashing at frequencies of 1 – 40 times per second. Various spectral/frequency combinations produced by the LGD have previously been demonstrated effective at either attracting or repelling different life history stages of several species of fish. Based on available literature into the spectral sensitivity of retinal photopigments of different species (e.g. Sillman et al 1990), the spectral output from the LGD can be tailored to exploit the sensory biases of target species during migratory life history stages. The effect of strobing light pulses at different frequencies remains unknown, however the LGD can easily be programmed to emit constant, low- and high-frequency flashes.

Light Guidance Device (LGD)

The use of light for fish management applications has been known for many years. Many studies have been conducted over the past 50 years but most have focused on “white” light or specific types of light projectors such as halogen lights or mercury vapour lights. Mercury vapour lights were selected because their spectral radiation is strongest in the blue-green region of the visible light spectrum, the region of greatest penetration in seawater (but not necessarily freshwater systems). With development of LEDs technology a wider range of light spectra exist and some of these lights are available commercially for underwater use. However, most of these devices, like their predecessors, are limited in that there is little or no flexibility in adjusting light spectra or frequency as well as light intensity level within the same device. However, this flexibility is required since species specific responses to light occur with some fish species attracted or repelled by light in the red spectrum whereas others are attracted to light in the blue-green region of the visible light spectrum. These behavioral responses can vary diurnally as well as seasonally with fish ontogenetic stage development. The Light Guidance Device (LGD) is unique in that it allows different frequencies of light, intensity and flash rate to be controlled by the user as indicated in Figures 1 and 2.  

Figure 1. Example Screen of LGD Device Showing Frequency, Intensity and Flash Rate Capabilities


Figure 2. Example Screen of a Single LGD Device. Several can be used together with same or different frequency


Lights have been studied in fish diversion projects at both hydro-electric and once-through cooling power plants for many years. Most “light” studies have involved both strobe light as well as mercury vapour light, and only limited information was available on the responses of fish to different frequencies of light. Light devices with the ability to alter frequency and intensity were generally not available as a research tool. Nevertheless, there are still several examples on where “white” strobe light has been effective as a repellant for some species (e.g. Coutant 2001, Patrick et al. 2001, Maiolie et al, 2001, Schilt 2006, Stantec 2007) but not others. Avoidance responses tend to more prevalent for pelagic species than demersal ones. For example, strobe lights were shown to elicit a behavioural response in Rainbow Smelt (Osmerus mordax) and displaced them 6 m in field tests in Lake Oahe, North Dakota (Hamel et al. 2008). It should be noted that strobe lights become less effective under turbid conditions. Based on mixed results for some species, white strobe light does not appear to have potential for widespread application at water intakes for all fish species given species specific responses (Allen et al. 2012). Applications will be species specific (e.g. Hamel et al. 2008).

Similarly, for mercury vapour light, there are numerous examples where light has proven effective as an attractant (Haymes et al. 1984, Rodgers and Patrick 1985, Stantec 2006). Figure 3 shows the application of mercury vapour light in attracting juvenile and smelt towards a fish pump at a power plant with and without lights operating.

Figure 3. Accumulation of Fish in Front of Bar Racks with and without Lights (from Haymes, Patrick and Onisto 1984 - click to view PDF Haymes et al 1984)


Still, there are other examples were mercury vapour lights have not been effective (Allen et al. 2006). Schilt (2007) concluded that light, both constant and flashing, has promise for fish protection and passage but that spectrum-specific differences in fish response, the effects of background and contrast and other aspects need to be explored. In addition, Noatch and Suski (2012) reported that lights and other non-physical barriers may be more effective when used in combination with other fish diversion systems. This can include fish pumps, angled screens, louvers and fish guidance systems.

As noted above, previous studies on behavioural systems using light devices have been limited in their exploration of light spectra for its potential use in freshwater fish guidance. Sullivan et al. (2015), using the LGD device capable of wavelengths between 400-670 nm, tested the responses of Largemouth Bass (Micropterus salmoides) to16 different light and light-pulse combinations. The colours of red, orange, yellow and green were considered with three light-pulse frequencies (120 min-1, 300 min-1, 600 min-1) as this species exhibits a high spectral sensitivity to red. LED technology provides new opportunities for using different light spectra and light-pulse frequencies to guide fish.


Reversed Louver Array

The primary function of louver systems is to divert juvenile and adult fish which may eventually become entrained through the turbines or impinged on the bar racks. A secondary function is to divert or minimize debris passing through the turbines. The system we propose to evaluate is operated in a “reversed mode” which offers numerous advantages over traditional bar racks or louvers (Figure 4). Differences between the configurations relate to the frame angle or the slat angle to flow which in the reversed louver example is much steeper. 

Figure 4. Configurations of traditional and reversed louvers demonstrating hydraulic effects on streamflow.


Potential advantages of this reversed configuration include the ability to divert debris as well as fish away from turbines or other powerplant structures, decreased occurrence of biofouling and the use of less construction material (for example, with increased slat spacing). Typically, a louver spacing of 2-5 cm between slats is effective in diverting fish but tends to lead to biofouling of the structure and creates hydraulic issues with flow alterations (Amaral and Dixon 2008, EPRI 2001). Increased spacing between slats without reducing the effectiveness of fish diversions may be achieved when other systems such as lights are used concurrently. If lights could be used to maintain high louver effectiveness at a spacing of 15-20 cm, louvers would present a more viable option to reduce fish mortalities at hydroelectric facilities. Early work has shown that even basic illumination of a structure will prevent passage as fish orientate to the structure (and flow) and are gradually swept towards bypasses along the louver array. Consequently, a louver presents fish with both a physical barrier and a behavioural structure. Fish avoidance response is expected from large schools encountering the louver since the entire school would respond as a single unit, and would be too large to pass through the louver slat opening especially in a reversed mode.

Carleton University recently evaluated an integrated system using ATET-Tech’s LGD equipped with adjustable wavelength and strobing output with a reverse‐configured louver rack to assess the effectiveness on downstream movement of age‐0 white sturgeon (Acipenser transmontanus). Incorporating the LGD operating at the most attractive setting with the louver spacings of 10 or 20 cm achieved the highest rates of bypass usage (100% and 97%, respectively) under both day and night conditions while the control treatment (no LGD or louver) resulted in the lowest bypass rate (46%) among fish that moved downstream. Further details are provided in Ford et al. 2017.


Barrier Nets

Barrier nets provide another example of one component of an integrated system. Barrier nets with mesh sizes of 9.5 mm or greater have been installed at numerous hydroelectric projects and power plants.  In northern locations, the barrier net is placed in front of the existing intake structure during the ice-free period which is typically April to November.  Under ideal conditions (e.g., proper hydraulic conditions, low approach velocity without heavy debris loading), coarse mesh barrier nets have been shown to be effective in reducing fish impingement (see Patrick et.al. 2014, below). Similar to stationary screens, barrier nets require a high level of maintenance. However, it is possible that a larger mesh size could be used with thicker cross-members illumnated with lights, thus reducing maintenance yet maintaining high performance for fish exlusion. This concept needs to be further evaluated.


Carleton University recently evaluated an integrated system using ATET-Tech’s LGD equipped with adjustable wavelength and strobing output with a reverse‐configured louver rack to assess the effectiveness on downstream movement of age‐0 white sturgeon (Acipenser transmontanus). Incorporating the LGD operating at the most attractive setting with the louver spacings of 10 or 20 cm achieved the highest rates of bypass usage (100% and 97%, respectively) under both day and night conditions while the control treatment (no LGD or louver) resulted in the lowest bypass rate (46%) among fish that moved downstream. Further details are provided in Ford et al. 2017.


An example installation is the Pickering Nuclear Generating Station (PNGS) on Lake Ontario which was evaluated using a variety of methods as shown in the figure below and involved ATET-Tech staff. The barrier net system consists of a series of interconnected net panels with a total length of 600 m.



Barrier Net Location - Pickering


Approximate sampling locations and placements (not to scale) of the Simrad EK60 echo sounder, DIDSON imaging sonar, gill netting, and underwater video cameras used at all aspects (south, east, and west) for the Pickering Nuclear Generating Station (PNGS) Fish Diversion System (FDS) barrier net effectiveness study, 2010. (Source: Patrick et al. 2014)


Publication attached: Patrick et al. 2014


Fish Pumps with LGD to Improve Performance

A fish collection and transport system may include the following components:

  • For fish transport, a fish pump such as a Hidrostal “fish-friendly” pump requires consideration especially if one requires fish to be collected and transported prior to being impinged on the screens;
  • Attraction system. Generally, there is a requirement for a fish attractant or guiding system to improve efficiency in transporting fish such as the use of lights as a directive cue. This is an application of the LGD (Figure below) where specific frequencies can be used to attract specific target species;
  • Fish transport pipe. Issues to be considered include pipe diameter, velocity in pipe, length of pipe, temperature in pipe, configuration (number of bends, etc.), and length of time in transport system;
  • Discharge location. The location of the discharge is important since it is preferred to transport fish into water bodies with similar temperatures as the source water.


There are several fish pumps which have been shown to effectively pass fish unharmed such as an Archimedes lift and Hidrostal pumps (McNabb et al. 2003). Hidrostal pumps are centrifugal screw type pumps which have been used successfully to pass fish unharmed to a receiving water body especially at low impeller speeds, and are well documented in the literature (Rodgers and Patrick 1985Patrick and McKinley 1987, McNabb et al. 2003, Helfrich et al. 2007). Factors considered important in the use of this pump include pump size, impeller speed, fish density, and flow volume. There can also be species specific mortality rates with some species having higher fish passage survival than others (Rodgers and Patrick 1985).


There is a requirement for a fish attractant to improve fish efficiency in collecting fish prior to transport. This is an application for the LGD to attract fish towards the fish pump prior to being impinged on the screens. For example, Rodgers and Patrick 1985, demonstrated the use of filtered mercury vapour light in increasing the performance of a Hidrostal pump in lab trials. The Hidrostal pump by itself, without directive cues, was not effective in capturing fish. For both rainbow smelt and alewife, capture efficiency increased significantly when the pump was operated in conjunction with the filtered mercury vapor light and other directive cues. Furthermore, lights have been shown as an attractant with a modified fish handling pump at an operating power plant (Haymes et al. 1984).


Light Guidande Device (LGD) - Field Unit