The goal of this project was to build an instrumentation buoy that would make it possible to monitor cod behavior in our offshore aquaculture net pen, 6 miles offshore. All the instrumentation needed to run of 12VDC power, a number of cables had to connect the buoy to the net pen, ~ 300 ft away and 50 ft below the surface, and, of course, it all had to be very waterproof. Below we describe the buoy and the instrumentation we used.
Our current instrumentation buoy for investigating the behavior of cod was built out of a buoys donated by the US Coast Guard. One of the waterproof chambers in the buoys contains 4-8 high capacity marine batteries (image at left shows Chris Rillahan and Adam Chouinard putting a rack of batteries in the buoy) and the other chamber contains the instrumentation (computer, HTI receiver, 4-channel digital video recorder, timers and router for wireless communication).
When deployed at sea, 6 miles offshore, the buoys is capable of continuously collecting data for ~6 days. A wind generator and solar panels supplement the power provided by 8, 100 Ahr batteries.
Cable lead from the buoy to the aquaculture cage located about 400 feet away. The cables are connected to three underwater cameras, 4 hydrophones, and a CTD that provides environmental data from inside the cage.
Data can be downloaded from the onboard PC through a wireless router.
The heart of the system is an HTI Model 591 receiver that is linked to a PC running the appropriate software package (far left). The 4 hydrophones (one is shown to the left connected to the net pen) are connected directly to the receiver. The hydrophones pickup pings emitted from transmitters inserted into selected fish, ~ every 2 seconds.
All data is stored on the PC hard drive and downloaded wirelessly once per week.
HTI pingers are activated and then surgically implanted into the body cavity of selected fish. Fish are anesthesized with MS222 and a single suture is required to close the incision. Fish recover within 10 minutes after surgery.
The pingers weight about 1 gram, they are about an inch long and they ping ~ every two seconds at a frquency of 307 kHz. Pingers can be turned on and programmed to different pulse widths and intervals prior to implantation.
In addtion to tracking fish with the HTI telemetry system we obtain video data from 3 underwater and 1 surface camera all day long, every day the system is in operation. Cameras are hard-wired to the Instrumentation Buoy and images are stored on a 4-channel DVR. The 250 gB hard drive can be swapped out each week so that videos, like the one shown to the left, can be analyzed while new data is being collected.