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Science Manual – Using Video Images for Fisheries Monitoring 21

configured. In reality, an image analysis system requires at least a portion of the

detected events to be verified visually by an operator.

3.7.2 Fishtick, the motion detection software system

Fishtick is an image processing software package developed by the Oregon-based

company Salmonsoft. It consists of a capture programme, FishCap, and a review

programme, FishRev. There are a number of different versions suitable for different

purposes. Fishtick Gold was assessed in this project and this is the version referred

to throughout this manual. FishCap captures images using motion detection or

tripwire algorithms. The user is able to configure the programme for a particular site

by setting regions of interest and then masking out areas within these regions (Figure

3.7) which may affect the capture process, such as weed waving in the current. The

motion detection algorithm compares successive frames, looking for a large enough

block of movement to be a fish. The user must set the size of the changed area

which will generate a detection as well as the pixel threshold where, if a sufficiently

large block of pixels shows enough change, a detection is triggered. Details of the

parameters which can be set and instructions on how to use Fishtick are provided in

Fishtick Fish Passage Monitoring System User’s Manual, included in Appendix 8.

This manual also gives the required PC specification for Fishtick.

Figure 3.7: FishCap display screen showing how a quad input can be

processed using four separate regions. An area of the top left image has been

masked off.

The tripwire algorithm uses a series of up to 25 ‘tripwires’ to detect fish; however, this

method works best when turbulence is low, water clarity is good, and lighting is

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