Study results: 1,570 potential derelict traps off the NH Seacoast

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

1. 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):

2. A higher volume of potential derelict lobster traps exists within 1.0 mile of the coast.  Density of inshore tracks  = 72.8 pdlt/mile
3. 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).
4. 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.
5. A lower volume of potential derelict lobster traps exists in areas of lowest density of active gear (Isle of Shoals, and offshore tracks).
6. 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.

Study results: there is a lot of trash and derelict fishing gear, and we're learning where to find it!

We are now releasing reports and results from Rozalia Project's work this summer. We are kicking it off with our most recent expedition, the Isles of Shoals neuston net study...

Rozalia Project discovers marine debris densities of up to 105,564 pieces and 2.25 miles of monofilament and rope per square mile in the tidelines and current convergences 

east of the Isles of Shoals

Rozalia Project for a Clean Ocean conducted a 4 day neuston net survey of marine debris density and type in the waters around the Isles of Shoals of New Hampshire and Maine. This expedition was funded and supported by the Bonnell Cove Foundation of the Cruising Club of America.

The objective of the survey was to identify if marine debris/derelict fishing gear was found in greater densities in the proximity of tidelines and current convergences and if so, in what densities and make up. This research was conducted by the Rozalia Project as part of a larger ongoing study to come up with marine debris detection and removal methods.

METHODS:

The survey was conducted from Rozalia Project's 60 foot sailing research vessel American Promise, utilizing a 1 x 0.5 meter, 333µ neuston net (provided by Sea Education Association), towed from a spinnaker pole 15 feet off the starboard beam of the vessel at speeds ranging from 1.4 - 2.2 knots. Survey tracks were run in depths of water from 65-330 feet.

The net was washed down when lifted out, to move items stuck on the net down into the cod end jar. The cod end jar was removed and contents sieved through paper towel. Fish, jelly fish and lobster larvae were returned to the sea immediately. The remaining sample was thoroughly inspected by eye for microplastics, fishing line and other marine debris. Once marine debris was removed, remaining organic matter and plankton were returned to the sea. All marine debris items collected were identified, catalogued and those under 2” stored. Larger items of marine debris such as plastic bags were recycled or properly disposed of on land.

Eight trawls, each 1 nautical mile in length were completed (see image below).

• Trawls 1 and 2 were conducted west of White Island, Isles of Shoals
• Trawls 3 and 4 were conducted on Old Scantum ledge, 8 miles SE of Isles of Shoals
• Trawls 5 and 6 were conducted 1-4 miles east of Smuttynose Island, Isles of Shoals
• Trawl 7 was conducted 2 miles west of Appledore Island, Isles of Shoals
• Trawl 8 was conducted 1.5 miles east of Smuttynose Island, Isles of Shoals
• Trawl 5 was the only trawl that was conducted through a visually identified tideline. Seaweed, foam and floating micro, meso and macro marine debris were all observed on the surface in this trawl area.
• Trawls 3 through 8 were conducted under sail

The ledges to the east of the Isles of Shoals are a convergent/upwelling zone on the outer bend of a slowing Western Maine Coastal Current (see figure left). This is potentially a temporary terminus area for marine debris that has travelled half of the Gulf of Maine Gyre past some of North America's busiest commercial fishing areas of Nova Scotia and Coastal Maine. In addition, it is an area in proximity to and encompassing marine mammal habitat and feeding grounds such as Jeffrey’s Ledge, seasonal home to minke, finback, and humpback whales as well as the endangered Atlantic right whale.

Using daily sea surface temperature satellite pictures, we identified where the cold water of the Western Maine Coastal Current upwelled to converge with warmer inshore waters, this convergence on September the 13th produced a  visually defined tideline, as we sailed 1.0 miles east from Smuttynose island on the Isle of Shoals. The tideline was in a SW-NE axis. We conducted Trawl 5 at a 90 degree angle to the tideline, and bisected it at the 0.5 nautical mile distance of the 1 nautical mile length trawl.

Right: This image was taken at 1800 UTC, September 13, 2011. The red lines to the left show the border between Maine, New Hampshire and Massachusetts. The convergence is labeled with a black line and the track of Trawl 5 in red.

RESULTS:

1. Trawls 1,2,3,4,6,7,8 yielded an average of 4.714 pieces of marine debris. This equals: 8,731 pieces of marine debris per nautical square mile
2. Trawls 1,2,3,4,6,7,8 yielded derelict fishing gear in the form of monofilament fishing line and rope/net fiber that made up 30.3% of the marine debris collected in these trawls
3. Trawl 5 bisected a visible tideline and yielded 57 pieces of marine debris. This equals: 105,564 pieces of marine debris per nm²
4. Trawl 5 yielded derelict fishing gear in the form of monofliament fishing line and rope/net fiber that made up 66% of the marine debris collected in this trawl
5. Trawl 5 contained 22 pieces of monofilament that averaged 3.2cm/piece totaling 70.4cm
6. Trawl 5 contained 16 pieces of rope/net fiber that averaged 9.6cm/piece totaling 154.1cm
7. Trawl 5 contained 224.5cm total length of monofilament and fiber. This equals 2.245 nm of monofilament and rope/net fiber per nm²
8. Tidelines and current convergences can yield up to:

• 105,564 pieces of marine debris/nm²
• 2.25 nautical miles of monofilament, fishing line and rope and net fiber/nm²

CONCLUSIONS:

1. More research is needed to increase the number of tidelines, convergences that are sampled by neuston net to give a good representative sample
2. There is a higher density of floating marine debris associated with visible tidelines and convergences
3. There is a higher density of floating derelict fishing gear associated with visible tidelines and convergences
4. The Western Maine Coastal Current has a high density of floating derelict fishing gear

FUTURE:

Rozalia Project is planning another expedition in 2012 to conduct neuston net trawls in tidelines and current convergences of the Western Maine coastal current. We will be working with the Blue Ocean Society of Portsmouth, NH, who have representatives on several whale watching boats. Their observers will contact us with the location of visible tidelines between the Isle of Shoals and Jeffrey's Ledge, allowing us to start mapping their location and size, as well as streamline our locating tidelines on a daily basis to run trawls. We also hope to partner with local draggers, lobstermen and tuna fishermen to provide us with additional realtime tidal data.

Jeffrey's Basin and Ledge are critical whale feeding areas, where a variety of marine mammals are frequently observed surface feeding. These areas of upwelling and current convergences with high densities of monofilament and rope/net fiber may also be locations where there are higher densities of plankton and copepods on which the whale feeds, thus increasing the risk of potentially harmful marine debris ingestion by the whales.

The high density of marine debris in these tidelines makes it feasible to remove. Rozalia Project is in the process of designing a trawl net that removes marine debris, but does not harm the plankton and other organisms that are bi-catch in the neuston net trawl. Our intent is that if results are successful, we will scale this marine debris net up to commercial size, so that fishing boats can be employed to trawl tidelines  for marine debris when they have exceeded fishing quota or due to grounds closure.

Thanks to this study, Rozalia Project is making the removal of marine debris and derelict fishing gear in the vicinity of the Western Maine Coastal Current a priority; for the protection of the oceans on the whole and the whales and marine mammals who call these waters home.

For more information about our work, to secure a berth on American Promise (intern opportunities available) or to support our work going into next season, please give Rachael a call 802-578-6120 or send us an email: rachael@rozaliaproject.org.

Stay tuned for next Wednesday's report about our side scan sonar survey for the Blue Ocean Society locating derelict fishing gear off the NH seacoast. And please remember to vote for us in the Interlux Waterfront Challenge facebook contest (last day to vote is Friday September 30th: https://www.facebook.com/interluxwaterfrontchallenge scroll down until you find Rozalia Project and click LIKE right under our description!