Issue 9, July 2009

VR2W Positioning System: More Tracks, Less Effort

In our March 2009 newsletter, we told you about how Dr. Terry Dick of the University of Manitoba used the VR2W Positioning System (VPS) to track the movement of lake trout. In this issue we tell you about how the Cal State Long Beach Shark Lab is now able to gather significantly more fish tracking data using the VPS than they used to be able to by doing active tracking, and with less effort.

Like any new technology, they needed to be sure that it worked properly. The Shark Lab validated the VPS by comparing its performance with their active tracking methodology. They double-tagged a shovelnose guitarfish and released it into Bolsa Chica, a west coast estuary, where a 16-receiver VPS system was running.

They simultaneously recorded its movement by using active tracking over a 24-hour period with a Vemco VR100 receiver and directional hydrophone. A portion of the two tracks is shown here:

A video of the two tracks can be seen here. The consistency of the two tracks is easy to see, as is the fact that there are many more VPS positions available than active track positions. The conclusion?

"Our results suggest that the VPS provides fine-scale data comparable to active tracking over the entire life of a coded transmitter (years), providing significantly longer term, fine-scale data for numerous individuals simultaneously." (Thomas J. Farrugia, Mario Espinoza, Christopher G. Lowe, California State University Long Beach Shark Lab)

The VPS at Bolsa Chica has been running continuously for about one year.

There are currently dozens of VPS studies worldwide in diverse environments such as lakes, rivers, estuaries, harbours, miles off the ocean coast, under ice, and at dams. The VPS is also well suited for unattended monitoring of remote locations for extended periods of time.