LOBSTER TRAPS AND DRIFTERS MONITORING SEA
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The photo shows the power of ocean waves on the instruments that measure the movement of ocean currents and why Manning, after losing a few commercially made “drifters,” started making less expensive homemade ones from inexpensive materials such as bamboo, aluminum, cotton cloth, and those big green leaf bags. This drifter was originally set in southwest Stellwagen Bank, between Cape Ann and Cape Cod. A park ranger found the poor, battered unit collapsed on a beach at Truro, on the Cape’s hook. He said it had been hit by easterlies.
“The goal,” Manning said, “is to get long-term data at the maximum number of fixed locations.” He then added, “Ultimately we’re trying to simulate not only temperature at the bottom, but also salinity and current. As physical oceanographers, we measure those three variables. We try to collect this information and feed it to ocean models the same way weather data is fed to the atmospheric models and the National Weather Service.
Yarmouth fisherman Elliott Thomas has been involved in the eMOLT project since 2003. “We started when we were doing the ventless or recruitment trap survey,” he recalled, explaining that the survey, “Tells you what size lobsters are present.” Funded through the Gulf of Maine Lobster Foundation, the survey, Thomas said, used traps at fixed locations rather than the random sampling used by Maine’s Department of Marine Resources (DMR).
These fixed locations made Manning realize he could use the same traps as platforms to measure other variables besides bottom temperature and record them hourly throughout most of the year.. Before eMOLT, he said he had been making do with a week or two of sampling per year on research vessels.
“Jim Manning asked if we’d all put temperature probes on our traps” recalled Thomas. “Then when the ventless trap survey ended, he asked, ‘Would you mind keeping going,’ and not everybody, but a lot of us said, ‘Sure.’ He’s such a great guy,” Thomas added, “It’s hard to say no to him.”
Temperature probe in a typical arrangement attached to a lobster trap for the EMOLT project. Jim Manning Photo
Thomas records water temperatures in Casco Bay at two depths: 7 and 12 fathoms (6 feet to a fathom). That information collected over the years has made it possible for oceanographers to detect the timing of the stratification and mixing of the layers of Casco Bay waters.
Casco Bay Long Island fisherman David Johnson’s traps, 15 miles offshore at 310 feet or 52 fathoms, record bottom temperatures 15 miles south of Cape Elizabeth for a year. Johnson said, and his records prove, the warmest bottom water temperatures come in November and December; the coldest ones, in May and June.
Vinalhaven fisherman Walter Day has also been tracking bottom temperatures for eleven years. His trap #177 rests at 31 fathoms. He said he’s allowed to move his recording traps sideways, but they have to stay at the same depth. Numbers 177 and 02, which he positioned up in seven fathoms collect temperature data between May first and Thanksgiving.
Thomas reported that Manning takes the recorded temperatures and puts them into graphs he then posts on the eMOLT.org website. “He has a page where he lists all the fishermen who are doing it,” Thomas said. “You click on the name and you see the data.”
Oceanographers use an instrument called a drifter to measure ocean currents, which are difficult to measure because there are so many layers of ocean waters. “What’s going on at the surface,” Manning explained, “is not what’s going on down below.”
After having lost a few expensive units to what Manning referred to as “the rocky shores of the Maine Coastline,” he started making homemade drifters using parts available at hardware stores and for about a third the cost.
(A drifter has a surface area of one square meter or close to 11 square feet. One type rides on the surface and another, attached to a drogue, or sea anchor, does its work under water.)
Middle School students who built a drifter for the EMOLT project. Jim Manning Photo
Drifter materials cost about $50, Manning said, adding that a cell-phone-sized transmitter and fees for satellite fixes come to another $550. The temperature probes the fishermen attach to their traps cost $250 each, Manning reported. “They record temperature every hour with 0.2 degC accuracy for ten years.”
The oceanographer explained that lobstermen helped him get started on this project in 2004 by helping him assemble the first student-built drifters and then putting them out. “Since then,” he said, “there have been more than a thousand more built. It’s a less expensive way of measuring currents than sticking a mooring in place and trying to maintain it for a long time.”
Who makes those thousands of drifters? Marine science students at Southern Maine Community College in South Portland made the first ones, but now grade school to college students from all over New England make them. In late May 2014, for example, Manning said 12 high school science teachers came to Woods Hole to learn how. They spent the day building a drifter then took the completed units back to where they teach to show students how to build drifters themselves. “It’s applied science,” Manning said.
“Just a week ago,” he said, “we put a drifter, made by fifth graders in Newburyport, MA, close to Monhegan. A week later, that drifter was about a mile off a beach at Newburyport. It came all the way home to those fifth graders.”
Students Ed Crosier and Conner Warren, interns with the drifter they built for the EMOLT project. Jim Manning photo
Manning would like to further expand the Drifter project outside of Penobscot Bay with student-built drifters because, he said, “We’re particularly interested in that section of the coast off Isle au Haut. “There’s an uncertainty where currents go,” he said. “They come down the eastern Maine coast, but do they get turned off to the middle of the Gulf, or do they turn down towards southern Maine? Sometimes they go out to sea.” He noted, “There’s a branch point there. We call this a ‘bifurcation’ and we’re always interested in getting drifters upstream of that.”This is current coming down from Canada,” Manning explained. “It’s holding a lot of lobster larvae, but it’s also holding a lot of harmful algae blooms, or red tide, and other things, so we’re always trying to promote drifter deployment off downeast Maine.”
Because early June is high season for the algae blooms, Manning said new moorings in southern Maine were detecting levels of toxicity. The drifter help demonstrates for the on- and offshore movements of coastal currents and therefore helps diagnose whether the algae blooms detected at the mooring may be getting closer to shore.
When asked about funding, Manning said, “It’s ironic that just as we’re starting to understand that there are changes in the environment that could potentially affect lobsters and many other species, the funding to carry on these monitoring programs has, if anything, gone down.” Even though, compared to some scientific operations, the eMOLT project is low cost, Manning said, “It’s a constant struggle to justify this program.” Although his small team is optimistic that in the future they’ll receive some kind of routine yearly funding, he said, “Right now we just scrounge around for grants here and there.”
These oceanographers with their eMOLT data are aiming for an ocean observing system much like the National Weather Service. “Wherever there are fixed gear fishermen,” Manning said, “they can contribute by volunteering their platforms to record bottom temperature, water salinity, and current as well as to deploy drifting instrumentation.”
(To see fishermen’s results go to http://www.emolt.org/. To see the tracks of drifters go to http://www.nefsc.noaa.gov/drifter and for instructions on how to build drifters and what to do with the data in the classroom, go to http://studentdrifters.org)
The Down East, Maine, Massachusetts, and Atlantic Offshore Lobstermen’s Associations helped Manning a great deal. Erin Pelletier, of the Gulf of Maine Lobster Foundation helped administer both eMOLT and Drifter projects. Southern Maine Community College helped start the Drifter project. The Northeast Consortium provided most of the initial funding; the Northeast Cooperative Research Program has helped in recent years.