A10. Video counting systems

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Figure A10VC4.jpg

1. Objectives[edit]

Source: Vaki riverwatcher. Source : www.aquatic control.co.uk. ; fishbio.com ; www.wav-stuttgart.de

Video-counting systems are widely used to study migratory fish populations. The method has multiple applications, for example:

  • Precisely count and obtain information on both anadromous (fresh water to salt water, e.g. salmon) and catadromous (salt water to freshwater e.g. eels) migratory fish.
  • Collect information on phenology and migration patterns in relation to environmental factors (e.g. temperature, flow etc.).
  • Obtain measures for individuals and ascertain population characteristics, size distribution among population.
  • Identify checkpoints/hotspots where new species are likely to populate.
  • Detect previously unknown sedentary species.
  • Evaluate ecological continuity by comparing video data obtained at different locations and structures, such as dams and weirs, across a river basin.
  • Check body condition of migratory fish.
  • Evaluate residency of some species in the fishway (e.g. catfish).

2. Method summary[edit]

The principle of video-counting systems is to count and identify fish. This is achieved by placing an underwater device, equipped with a camera, to film a channel were fish are funnelled through individually. This can be a fishway, or a specifically designed barrier that allows counting on natural, undammed rivers (see pictures below). Cameras are linked to a computer that records the video, which can be downloaded for post-processing and quantification at a later date. Post-processing encompasses several steps, including the application of filtering algorithms that enable the operator to discriminate objects erroneously identified as fish, e.g. leaves or branch, thus mitigating against false positives. Additionally, adjusting the brightness and contrast of the video image, enables the operator to view select fish more easily. While some systems are efficient and time-saving each has its own advantages and limitations (Eatherley et al., 2005), and care and prior thought should be taken to ensure the system selected suits the conditions of the study area.

3. Advantages[edit]

Source: Vaki riverwatcher. Source : www.aquatic control.co.uk. ; fishbio.com ; www.wav-stuttgart.de
  • Large quantity of information collected, providing a detailed dataset which can be analysed.
  • Some systems automatic database on fish population numbers, individual size (not all systems) and direction of migration (not all systems).
  • Suitable for long-term studies.
  • Equipment is lightweight and can be redeployed for use on other sites.
  • The use of software to automatically distinguish videos sequences containing fish from those that contain objects that are not (e.g. branches, leaves etc.) increases the time efficiency of the method.
  • Remote data transfer is possible if there is internet access.
  • Can be coupled with PIT-tag antennas (not all systems).
  • No fish handling, reducing stress to fish.
  • Some systems are coupled with IR optical beam counter for scanning and mapping the fish.
  • Method is reliable during unsettled conditions.

4. Disadvantages[edit]

  • Expensive.
  • Complicated to retrofit fishways and locations not designed with the installation of the device in mind.
  • Requires routine maintenance (e.g. cleaning parts of the device that is underwater, computer maintenance, removal of detritus in fishway etc.).
  • Can become a predation spot for some sedentary fish (e.g. trout, catfish) especially because the funnels induce a concentration of prey.
  • Does not function in turbid water during floods.
  • Can be damaged in streams with active bedload, e.g. alpine streams.
  • If the water flow is too slow, fish can stay in the channel, obstructing the camera view.
  • Misidentification of detritus (e.g. leaves, branches etc.) as fish can occur during high turbidity events; this can be mitigated during post-processing.

5. Recommendation for method application[edit]

  • The installation of the device needs to be considered during the design/planning stage of the structure (i.e. weir or dam) into which it will be integrated. Meet with the device contractor as soon as possible.
  • Where a device is being installed into a weir or dam that is already constructed specialist advice will be required to inform best way to retrofit the structure.
  • Consider the need to install an internet connection for accessing device remotely. This allows for desktop checks on functionality and remote data transfer.
  • Installation design and selection of device should consider safety issues surrounding cleaning and maintenance, consider devices that are easy to lift and/or access.
  • Routine checks and maintenance of the device may need to be scheduled depending on local conditions, e.g. rate of algae and macroinvertebrate growth etc.
  • Get a contract with maintenance and insurance for device.
  • There are several devices available each with specific properties; ensure background research is thorough to help select device best suited to specific site characteristics.

6. Costs[edit]

Expensive to get a powerful and durable tool, between several thousand and tens of thousands of pounds. Cost estimates can be found at: https://www.gov.scot/publications/technical-logistical-economic-considerations-development-implementation-scottish-salmon-counter-network/pages/8/

7. Data analysis[edit]

Source: Vaki riverwatcher. Source : www.aquatic control.co.uk. ; fishbio.com ; www.wav-stuttgart.de

From the devices only carrying cameras, without any measuring apparatus:

  • Species richness and abundance.
  • Populations phenology.
  • External indicators of fish health.
  • Fish behaviour. Note, this will only be within the field of view of the device.
  • Passability of a fishway, depending on flow conditions.

From devices allowing fish measurements:

  • Cohort and population characteristics assessment.

From devices dedicated for downstream migration:

  • Recruitment, i.e. number of fish that survive to enter adulthood.
  • Adult survival after reproduction.

8. Surveys[edit]

After installation recording can be carried out continuously offsite.

9. References[edit]

  1. Eartherley, D. M. R., et al. (2005). Trends in Atlantic salmon: the role of automatic fish counter data in their recording. Scottish Natural Heritage Commissioned Report No. 100 (ROAME No. F01NB02). UK.
  2. https://www.gov.scot/publications/technical-logistical-economic-considerations-development-implementation-scottish-salmon-counter-network/pages/8/

10. Gallery[edit]

Video - https://www.gwct.org.uk/blogs/fisheries-blog/2020/june/video-watch-returning-fish-pass-through-our-counter/?utm_source=All+Contacts&utm_campaign=0943cedb6f-Non-Mem-NL-090620&utm_medium=email&utm_term=0_dd843c5cb6-0943cedb6f-27774948&mc_cid=0943cedb6f&mc_eid=cf738415c4