VEMCO - VR2C Manual
9
Jul 2018
45
4
Attachment Methods
How a VR2C is deployed is driven by the environment in which it is being deployed and the type of study
being performed. Some important points to keep in mind when designing a deployment plan for your VR2C
receivers are explained here. The common method for attaching a VR2C to a mooring line is also given,
along with the dimensions of the VR2C cases.
4.1
Deployment Facts/Tips
4.1.1
Mooring
VR2C receivers are moored in many configurations often
reflecting the bathymetry and oceanographic/weather
conditions. A simple mooring design generally works well.
However, in rougher conditions, heavier weights and
mooring lines are usually required. If a bottom mooring is
desired, the VR2C should be positioned above the floor such that it has an unobstructed “view” of tagged
animals within their expected acoustic range. Ensure the VR2C’s hydrophone is unblocked (e.g. do not
position an air filled buoy directly above the hydrophone) and free of any biofouling. In high flow locations,
you may consider using hydro-dynamically shaped buoys and low profile anchors.
For the best horizontal range, mount the VR2C receiver in a
vertical position. If the VR2C is deployed close to the
bottom, mount the VR2C with the hydrophone pointing up to
the surface. If the VR2C is deployed close to the surface in
deep water, then position the VR2C so the hydrophone is
pointing down.
4.1.2
Spacing
Receiver spacing is generally determined based on range testing and historical acoustic data. Our
recommendation is that you should try to space receivers such that you achieve good detection probability in
most or all weather conditions. It is not always necessary to have 100% coverage if you have several other
locations where you know the animals will be passing through. However, if you wish to accurately quantify
the passing of animals through receiver locations then you should strive for 100% detection probability.
Typical spacing is usually between 100 and 1,000 meters depending on environmental conditions and the
output power of the tags used in the study.
4.1.3
Biofouling
Some customers use a rubber shrink tape, such as DAFLEX ST250 Cold Shrink Tape,
available from Digikey (W211-ND), to prevent biofouling on the VR2C receiver. It can be
used to cover the receiver body (don’t cover the hydrophone) and does not leave a glue residue
when removed. Another option is to use an antifouling paint, such as Interlux Micron CSC.
CAUTION:
The hydrophone must
be kept
free of mooring lines
and obstructions
. Objects
around the hydrophone will
adversely affect the detection
range of the VR2C receiver.
Never cover the Status Light (LED)/Release Valve.
The release valve
must
be able to pop open if needed
and must not be blocked by tape or paint.
The VR2C underwater cable must
be appropriately
strain relieved
to
ensure that no strain is placed on
the cable connection to the receiver.
NOTE:
Keep the
hydrophone
uncovered
to prevent
acoustic
dampening.
