Currently, we are using a custom-made underwater videography to assess the boundaries and health of oyster reefs in NH. The video system consists of an underwater black and white camera (Aqua-Vu model IR) with integral infrared lighting mounted on a steel frame, Garmin differential GPS unit (Model GPS 76), laptop PC for navigation and GPS datalogging, and Sony digital video camera (Model DCR-TRV103) for recording. The entire system was assembled for approximately $3,500. In typical operation, the frame with camera is suspended in the water column with a steel cable on a manually operated winch. After positioning the camera at a height suitable for obtaining adequate image quality, the unit is slowly towed (at speeds up to about 1.5 knots) so that it remains directly below the winch. The video image is split onboard to a camcorder for recording and a monitor so the operator can see the imagery in real time. This allows for quick adjustments of the camera as the survey proceeds. Ship tracks are monitored in real time on the PC which has navigational software installed, and GPS data are logged. The video imagery and GPS data are synchronized by time which is recorded in both datasets.
Nannie Island Oyster Reef
The Nannie Island reef is the largest (about 30 acres) and most productive in waters approved for harvesting in New Hampshire, but this video reveals the fact that it is heavily worked by tongs, the most common harvesting method used in this area. Its overall appearance is similar to the Piscataqua River reef described above. When this video was taken, seaweeds were quite dense in some areas (and caught on the camera frame) and the infrared lights were used (see "washed out" look near center of imagery).
Piscataqua River Oyster Reef
A survey done in the early 1970s by the State of Maine found "oyster bottom" extending along several miles in the deep channel areas of the Piscataqua River. Only a few areas have been surveyed recently, and this video is typical of what has been found: reefs consisting mostly of single oysters or small clumps with very little vertical extension and most oysters lying on their side. Some reefs in this general area have been harvested in recent years by small dredges, but the extent of harvest has not been documented.
Squamscott River Oyster Reef
This imagery was taken as the video system was slowly towed across a natural, undisturbed oyster reef in New Hampshire. Most of our still productive reefs (see
Oysters in New Hampshire) are regularly worked by harvesters using tongs and have very little vertical relief. The reef in the video, however, is in an area where harvesting is prohibited. Note the presence of many clumps of oysters that extend vertically several centimeters into the water column; this is particularly visible as the camera rocks back and forth near the end of the video. Also notice where the reef drops off into the channel, and an area that appears to have been damaged (by boat anchor?) near the end of the video. This reef had an average of about 500 oysters per square meter (all size classes) when this video was taken, a density that is about 10-fold the typical density found on harvested reefs in New Hampshire, such as those below.
