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- Evaluating migration of fish over man-made structures such as fish ladders or weirs.
- Allows for the assessment of these conservation practices.
-  Quantifying migration patterns of salmon and trout
(Lucas and Baras, 2000)

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Do you think you can apply fish counters to solve a ecological problem in your community or elsewhere? 

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Do you think you can apply fish counters to solve a ecological problem in your community or elsewhere? 

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The estuaries and tidal rivers in the town I teach are in the process of being restored. Fish counters could be used in the areas to assess the improvements made by the restoration. (Salt Marsh Restoration Program, n.d)

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One of my units in marine biology is continental shelf ecology. We use the event below (released Atlantic salmon into native Pacific salmon fish stock) as our driving phenomena. I can have my student work with the data collected from the fish counters to see the impacts of the nonnative population on the native ecosystem.

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Fish farm caused Atlantic salmon spill near San Juans, then tried to hide how bad it was, state says

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A Washington state investigation of the catastrophic net-pen collapse in August at Cooke Aquaculture's Cypress Island fish farm finds the company at fault for a disaster that freed more than twice as many Atlantic salmon into the Salish Sea as...

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Example of a fish ladder in Scotland with various automatic fish counters(Eatherley, et al., 2005).

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In 2003 there was a significant drought which preventing many fish reaching their spawning grounds. Data collected using the fish counters showed a drop from the average 1631 to 97. This information drove government officials to action. (Eatherley, et al., 2005)

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The Tweed River provides 15% of Scotland's freshwater Atlantic salmon habitat. Automatic fish counters were installed on existing in-river structures to assess the abundance of Atlantic Salmon in the system. Data collected inspired a catch-and-release program, revealed interesting behavioral patterns, and helped obtain emergency releases of reservoir water. (Eatherley, et al., 2005)

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See attached document for literature cited

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- Many errors can occur including missed counts, false counts, mixed counts, and multiple counts (Eatherley, et al., 2005).
-When two fish enter at the same time it only recognizes them as one fish.
- There has been documentation of fish avoiding the structure and changing behavior, which may skew the data (Baumgartner et al., 2010).

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As of 2005 there were 29 fish counters in use in Scotland to assess the impacts of human made structures on native salmon stock and migration (Eatherley, et al., 2005). The counters are embedded in river structures such as weirs or fish ladders.

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Uses light beams that are disrupted as the fish pass though them. (Thorley et al., 2005)

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Uses principals of sonar (Casselman et al., 1990).

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Sense the change in electrical resistance of the surrounding water (Lucas and Baras, 2000)

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Although fish counters are not suited for citizen science, the data that they collect can be valuable for my students as I work to inspire civic engagement and stewardship.

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- Can only be used for small populations sizes, which is why they are used less frequently in North America (Eatherley, et al., 2005).
- Less accurate when counting fish at higher migration rates. Only 76% accurate at rates exceeding 1,500 fish/h (Shardlow and Hyatt. 2004).
- Some versions do not work in areas with high turbidity or salinity (Baumgartner et al., 2010)

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- Expensive
- Must be associated with a suitable in-river structure
- Require regular monitoring
(Eatherley, et al., 2005)

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- Many other fish stock monitoring tools are capture dependent.
- While those methods provide more information, they disrupt the fish' natural behavior and many cause stress.
(Lucas and Baras, 2000)

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1. More efficient than visual observation

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1. More efficient than visual observation

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- Does not disrupt the natural behaviors of the fish
- Data can be collected from more inaccessible locations
- Requires less people
(Lucas and Baras, 2000)

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fish counters are often used to assess the impact of man-made barriers on the local fish stock (typically salmon or trout). See the attached video to view the application of a fish counter to a migration ladder.

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A Fish Ladder with a Vaki Riverwatcher Fish Counter

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Fish counters are used to estimate fish population sizes and dynamics without needing to capture the fish. The device is placed in a stream/river and as the fish swim past, the device senses their movement. (Casselman et al., 1990; Baumgartner et al., 2010) The device can also capture other information including upstream or downstream direction, body depth, and silhouette image (Shardlow and Hyatt. 2004).