1,570
Potential Derelict Lobster Traps located during 4 days of Derelict Fishing Gear
Sidescan Sonar Survey: Portsmouth, NH and the Isle of Shoals
Rozalia Project for a
Clean Ocean conducted a 4 day sidescan sonar survey to locate derelict fishing
gear around the coastal waters of Portsmouth, NH and the Isle of Shoals on the
behalf of the Blue Ocean Society for Marine Conservation, NH Sea Grant and UNH
Cooperative. The Sonar survey was conducted as part of the Marine Debris to
Energy Project, a NOAA funded project to detect and remove marine debris along
the coastline from southern Maine to northern Massachusetts. The Sonar survey
was also supported by Optima Bank, Portsmouth, NH and the Kittery Point Yacht
Yard, Kittery, ME.
METHOD:
The survey was
conducted from Rozalia Project's 60ft sailing research vessel American
Promise utilizing a Tritech
Starfish sidescan sonar towed from the starboard quarter of the vessel at
speeds ranging from 1.9-4.3 knots, in depths of water from 20-135 feet.
The aim of the survey
was to locate derelict fishing gear and investigate it's volume and
geographical distribution, in this case predominantly derelict lobster traps
(pots)
Potential derelict
lobster traps were identified on the sonar image by the following criteria: red
dots=potential derelict trap, blue dots=active trap. The following examples are
from the sonar survey:
1: Groups of 3 or more lobster traps clumped
together in close proximity:
2: Trap line of 3 or
more with v shape or large deformation of the multi-trap line:
3: Individual traps
with no active gear nearby:
4: Trap lines with no
active lobster buoys within the Starfish’s range:
When potential
derelict lobster traps where viewed on the sonar display, a snapshot was taken
from the sonar image. In addition, waypoint locations and track information
were recorded on an iPad utilizing Navionics charting software with snapshot
time, waypoint number, track number, track start and finish GPS positions and
track start and finish times recorded on data sheets.
RESULTS
1: Portsmouth
Harbor/Piscataqua River Entrance (Fort Constituition to Gunboat Shoal):
- 30.18 potential derelict traps per mile
- 9 tracks totaling 11.1nm were surveyed with
335 potential derelict lobster traps located
2: Gunboat Shoal to
Rye Ledge:
- 102.86 potential derelict traps per mile
- 9 tracks totaling 10.14nm were surveyed with
1043 potential derelict lobster traps located
3: Isle of Shoals:
- 25.95 potential derelict traps per mile
- 7 tracks totaling 7.4nm were surveyed with 192
potential derelict lobster traps located
Survey totals:
- 1,570 potential derelict lobster traps
located
- 28.64 miles of ocean were surveyed
- 296 waypoint locations of potential derelict
traps recorded on sonar
CONCLUSION
- Clumps/groups of lobster traps are often
located at substantial terrain changes, for example, from sand to rock
ledge (see below – ledge off Rye Harbor):
- A higher volume of potential derelict
lobster traps exists within 1.0 mile of the coast. Density of inshore tracks = 72.8 pdlt/mile
- A higher volume of potential derelict
lobster traps exists in proximity of highest density of active fishing
gear (recommend ROV survey to confirm accuracy of sonar survey in these
high density active trap areas).
- A lower volume of potential derelict lobster
traps exists offshore beyond 1.0 mile of the coast. Density of offshore
tracks = 37.7 pdlt/mile.
- A lower volume of potential derelict lobster
traps exists in areas of lowest density of active gear (Isle of Shoals,
and offshore tracks).
- Derelict lobster traps are not static,
during the survey, American Promise re-surveyed a shipwreck that was part
of a 2008 Sonar Survey (below). During the 2008 survey the top of the wreck was
covered by over 20 derelict traps. During our 2011 survey, the sonar image
shows a wreck with no derelict lobster traps on it, just an active trap
line to its port side. More research is needed on what moves the traps
around (storms, draggers?) and where they go.
In the opinion of the
Rozalia Project, the waters of coastal New Hampshire and the Isle of Shoals
have a significant amount of derelict fishing gear on the sea floor with
several inshore (within 1 mile of coast) locations where it has accumulated
that would make removal of the derelict fishing gear feasible.
Rozalia Project picked up its first piece of Pacific marine debris (the first of many!) with the VideoRay ROV Tuesday! Thanks to Nancy Richardson and the crew of the tall ship Exy Johnson, we had a very cool launch pad as well. The Exy Johnson is docked along the main channel of the Port of Los Angeles and we went aboard to show off the VideoRay Pro 4 and our trash-hunting capabilities to some great people from ReGreen, the Cabrillo Marine Aquarium, and the LA Maritime Museum.
