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Science Manual – Using Video Images for Fisheries Monitoring 1

1 Introduction

This manual details the equipment and methods required to record underwater video

images and to use them to monitor and count fish. It outlines the combination and

arrangement of camera, lighting, image recording equipment, motion detection and

image analysis software for a variety of applications related to monitoring fish. The

technique can be used to validate existing fish counters (resistivity, infrared, acoustic)

or as a stand-alone counting system.

The specifications given for system components can be found in commercially

available off-the-shelf products, or can be met by manufacturers to a design

appropriate for the technique.

This work was developed under Environment Agency project, Development of a fish

counting system for fish passes. The full range of outcomes from this project, of

which this manual is one component, is listed below.

• A fish counting system costing less than £5,000 suitable for fish passes and

narrow channels, and an assessment of its performance.

• A guidance manual for using underwater cameras, lighting and image

analysis techniques to monitor fish.

• Standard designs for the fish exit of a fish pass for the routine deployment of

video monitoring equipment.

• An automated motion detection system for fish, developed to meet

Environment Agency requirements.

• An automated image analysis system for counting fish, based on an interface

with commercially available hardware.

• Material for a workshop titled Using video images for fisheries monitoring.

• A statistical model for improving the accuracy and precision of fish counts

using an automated motion detection or image analysis system.

The methods outlined here use relatively cheap components, are easy to build, install

and maintain and have demonstrated their ability to produce reliable results with

modest use of staff time.

1.1 Use of video images

There is no universal tool for counting migratory fish in a river and there are

situations for which a reliable technique does not exist. Video can be used in cases

where other methods would be inappropriate or prohibitively expensive for the

required purpose, such as:

• monitoring the effectiveness of newly constructed fish passes;

• obtaining data for the approval of existing fish passes;

• studying fish behaviour;

• whole river counting for returning stock estimates.

Absolute validation, that is, an accurate record of how many fish actually passed the

counter and when, is very difficult to achieve. Cameras are used to obtain such a

record, but under conditions of high turbidity and flow it can be impossible to be

certain that all fish are visible and so it becomes more of a comparison. Video

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