User manual

Science Manual – Using Video Images for Fisheries Monitoring 3
2.1.2 Sizing
A simple method of sizing by reference point has been integrated into both the image
processing techniques outlined in this report (Fishtick and DVMD). The user clicks
on two points within the view a known distance apart (at approximately the same
distance from the camera as the fish) in order to calibrate, before measuring the fish.
A simple calculation then determines fish length from the calibration. All that is
needed for this method to work are a number of markers at known distances from the
camera. This method can therefore work with all of the systems described in Table
2.1. However, under certain conditions, it may not be possible to place markers or to
accurately estimate the distance of the fish from the camera, for example with
upward-looking cameras with no structure in the view.
2.1.3 Fish behaviour
Avoid mounting equipment in areas where fish may hold. This may mean deploying
on the downslope of a Denil or Larinier pass.
2.2 Logistics
2.2.1 Mains power
Some system configurations may not lend themselves to running on battery-powered
systems, even with an on-site method of keeping the batteries charged. Wide fish
passes which require lots of lighting are an example. Strategic or long-term
monitoring sites would also benefit from mains power; it may be more cost-effective
to install mains power where equipment is likely to be deployed for a number of
years.
There are plenty of options for powering a system where mains power is not
available (Section 3.2). Low-power charging options are not included in the system
descriptions here, as they are very site-specific. Add whatever is chosen to the total
cost of the system
2.2.2 Equipment maintenance
Don’t forget to factor the time needed to clean cameras, light panels and white
boards into your fish counter budget. During the summer months cameras will need
to be cleaned at least every two weeks. Sites where debris is likely to accumulate
will need regular checking and maintenance all year round.
2.2.3 Access to equipment
Equipment maintenance should be borne in mind when planning a fish pass counter
site, as you will need to be able to access equipment over a range of river flows. You
are likely to lose data if you have a fish pass in the middle of a river with only wading
access. As soon as the flows increase, you will be unable to safely reach the
equipment to clean cameras, remove debris or repair any damage.