By KATIE MOSHER
During yellowfin and bigeye tuna seasons, or in search of swordfish, boats from Wanchese head 40 miles offshore to waters near the continental shelf’s edge. Captains and mates set longline gear in late afternoon or at dusk, in hopes of bringing home a good catch. But that catch may also be a temptation for pilot whales that normally dive deep in pursuit of squid.
Thus, despite the crews’ overnight attention to the lines, sometimes predators, including pilot whales and sharks, risk injury to take the tuna or swordfish as a more filling and easier meal — often leaving behind only the fish head on the hook.
Any loss affects a captain’s bottom line. And if a pilot whale were to become entangled in lines during its dinner excursion, the crew, boat and animal could all be in danger. This summer, scientists and fishermen will continue research in efforts to keep pilot whales from feeding on the easy meals provided by commercial fishing lines. Both groups would rather the whales go after more traditional fare, such as squid.
“Our ultimate goal is to document how animals are physically interacting with the gear: How are they taking the tuna off the line?” says Andrew Read of Duke University Marine Laboratory. “Then we can help to prevent pilot whales from taking the tuna.”
For Captain Dewey Hemilright of FV Tar Baby, participation in the collaborative research is an effort to keep the fishery open and in compliance with federal regulations that protect marine mammals.
“We are working on the problem,” explains Hemilright, who has been fishing for more than 20 years. “We don’t have another choice. A judge could shut us down.”
In 2007-08, Read led a pilot whale study funded by the National Marine Fisheries Service (NMFS), part of the National Oceanic and Atmospheric Administration (NOAA). Since 2004, North Carolina Sea Grant has administered several NMFS research programs designed to provide information to groups of researchers, managers and fishermen who serve on marine mammal Take Reduction Teams.
The success of the initial research has been due, in part, to the cooperation of longliners based on the Outer Banks, Read notes, citing in particular Hemilright and Matt Huth, captain of the FV Finnali.
This year, Duke researchers are working with Hemilright to expand the study through the N.C. Fishery Resource Grant Program. Known as FRG, the program is funded by the N.C. General Assembly and administered by North Carolina Sea Grant.
Building upon the combined results of the previous research cruises, the new study focuses on high-tech acoustic tags — this time tagging animals swimming closer to the longline gear.
‘To solve the entanglement problem would be a win-win,” Read says.
Commonly called pilot whales, the genus Globicephala is actually within the dolphin family. Although not classified as endangered, short-finned and long-finned pilot whales are included in the Marine Mammal Protection Act.
Like many sea birds and sea turtles, tuna and pilot whales are considered pelagic animals — roaming the open ocean. Although tuna and pilot whales range from Newfoundland to Florida, studies have focused on an area off Cape Hatteras that has extensive fishing and a high number of pilot whales.
“Attempts to reduce interactions between pilot whales and longline fishing gear have been hampered by a lack of information regarding the nature, timing and cause of these interactions,” Read explains.
Hemilright joined the NMFS Atlantic Pelagic Longline Take Reduction Team (PLTRT) in 2008 to ensure that the North Carolina fishermen’s perspective is represented. “I hope that my participation shows what is really going on,” he says. “If you don’t help paint the picture, it will be painted without you.”
Before Hemilright came aboard, the panel had already drafted a take reduction plan. “We voiced opposition. Our livelihoods are at stake,” he says of response to the initial draft that had been developed without representatives of North Carolina’s longline fleet.
A final rule, published in the Federal Register on May 19,2009 and based on the PLTRT’s draft plan, calls for serious injury and mortality of pilot whales from commercial fishing operations to be at “insignificant levels,” or a near-zero rate, within five years, explains Erin Fougeres, NMFS coordinator for pelagic longline take reduction. The final rule will become effective on June 18,2009.
The rule creates a Cape Hatteras Special Research Area (CHSRA) about 35 miles offshore. The CHSRA includes all waters inside and including the rectangular boundary described by the following lines: 35 degrees N. latitude; 75 degrees W. longitude; 36 degrees 25′ N. latitude; and 74 degrees 35′ W. longitude. Vessels wishing to set longlines in the CHSRA will need to provide NMFS at least 48 hours notice of a fishing trip. Captains must agree to accept federal observers on selected trips and to participate in research when requested.
The rule limits longliners in the CHSRA and a wider Atlantic region to a 20-nautical-mile mainline. Captains will need to post an informational placard regarding marine mammals in the wheelhouse and on the working deck. Marine mammal training has already been added to mandatory workshops for pelagic longliners to learn techniques to avoid by catch of protected species.
Even after the final rule is in place, the PLTRT will review the implementation of the plan over the five years, with attention to ongoing monitoring, research and other evaluations. “The plan is an adaptive management approach,” Fougeres explains.
Thus the North Carolina research findings will continue to be critical factors as the team decides “where to move next in the plan,” she adds.
Along with Read and Hemilright, the field studies include Danielle Waples and Kim Urian, Duke research associates who have worked with various North Carolina fishermen on projects to reduce bycatch and entanglement of marine mammals and sea turtles.
A suite of data collected in 2007-08 on the pilot whales off Hatteras included behavioral observations, digital images taken to identify individual whales, acoustic recordings, and tissue samples for species identification.
The 16,000 digital photos will help identify individual animals and their associations in family pods. “The database will allow us to determine if particular individuals are resident in this area, and if certain whales are responsible for the depredation,” Urian explains. “We have already seen some of the same whales in both spring and fall of 2007 and 2008.”
It’s not surprising that pilot whales, like fishing boats, return to particular areas. “Pilot whales can anticipate where gear will be set within 10 to 15 miles,” Read explains. “It is easy for them to find the longlines.”
Analysis of the photos includes documenting healed scars — often near the lip or mandible — that indicate previous encounters with gear. The scientists want to know if particular individuals are injured by the gear. “We are interested if certain individuals, or age or sex classes, are responsible for depredation,” Urian notes.
The researchers also are interested in how behavior — such as the taking of tuna off the lines — can be learned by new generations of pilot whales. The animals are known to travel in family or social groups called “pods,” making it possible for younger whales to learn from their elders. Shared learning among different pods may also occur. The researchers have reported seeing hundreds of animals within a day, representing multiple pods resting together at the surface.
The Duke team also is building a tissue database that provides genetic information from skin samples collected from 61 individual pilot whales. Analysis by Patricia Rosel of NOAA’s Southeast Fisheries Science Center Marine Mammal Genetics Lab in Louisiana revealed that all 61 animals were short-finned pilot whales, rather than a mix of the short- and long-finned species.
The researchers are particularly excited by initial data gathered with new high-tech Digital Archive Tags or DTAGs. In 2008, five of these tags were attached to pilot whales with suction cups to provide baseline information on the animals’ feeding habits away from the fishing gear.
“One pilot whale dove to approximately 600 meters,” Read recalls. The DTAGs yielded a great deal of useful information, and the researchers are eager to tag animals closer to the fishing gear.
Although most scientific observations are made from aboard research vessels or on the fishing partner’s vessel, the tagging and tissue sampling are done from much smaller boats — and with special permits — in order to get closer to the animals.
The small, lightweight tags are placed near a pilot whale’s dorsal fin. Long carbon poles allow the scientists to reach the animals, and the tags are attached with four silicon suction cups. Prior to tagging a pilot whale, the scientists program a release mechanism to set the length of time the tag is attached.
“The DTAG is equipped with a pressure sensor, three-axis magnetometer and accelerometers that measure depth, heading, pitch and roll five times per second,” Read notes. Two hydrophones record stereo sound continuously at a sampling rate of 192 kilohertz.
A VHP antenna allows radio tracking of the animal while it is at the surface, and helps researchers to find the tag — and the valuable data — after the tag releases from the pilot whale.
The scientists visually follow tagged animals surfacing during daylight hours, recording location, group size and composition. Analysis of dive data from night hours reveals patterns of dive duration and depth, and acoustics associated with the animals’ use of echolocation.
In the 2008 study, the tags recorded dives to 596 meters, lasting up to 15 minutes. One of the tagged whales not only dove deeper at night, but also ventured farther from the Continental Shelf where the pod congregated during the day.
Waples reports that foraging dives of more than 100 meters included clicks, which then stopped during the return ascent. The team also identified rapid clicks — described as a buzz — as the pilot whales actually attempted to capture prey.
In the new study, the researchers will place tags on pilot whales closer to fishing gear, then compare the animals’ activities with the baseline feeding data. An engineer from Woods Hole Oceanographic Institute will join the group to work with the tags.
The team will again take digital photos. And sensors on his mainline will record “vocalizations” if pilot whales are nearby.
Each step in the ongoing research process requires data to be analyzed so that the next step can be defined. “It is like finding a cure for a disease,” Hemilright explains.
Ultimately, the research project’s “win-win” goal would allow the fishing boats to identify areas and set the best gear to target species such as tuna, while at the same time limiting interactions with marine mammals. It is in the fishermen’s best interest to get more fish on each fishing trip, the scientists and fishermen agree.
“This is not just an issue for North Carolina or the United States. It is a global problem,” Read adds, citing similar problems in the Pacific and Indian Oceans, among others. Scientists working in the Pacific — to limit entanglements by false killer whales — have joined Read’s research cruises to learn more about the Duke team’s data-gathering protocols.
As president of the Society for Marine Mammalogy, Read shares results with colleagues, and provides data for the Ocean Biogeographic Information System, part of the international Census of Marine Life.
Read says that his scientific crew has a definite advantage in gathering relevant data. “The North Carolina fishermen are very willing to be active participants in the research.”
Hemilright agrees. “If you give a fisherman a problem, he will find a solution.”
For more information:
- NMFS – Atlantic Pelagic Longline Take Reduction Team: http://www.nmfs.noaa.gov/pr/interactions/trt/pl-trt.htm.
- Ocean Biogeographic Information System OBIS-, SEAMAP: http://seamap. env.duke.edu/
Longline fishermen consider sea conditions and presence of predators when choosing when and how to set gear.
For example, they will set gear early if they know that sharks have taken catch the night before. And they may adapt the arrangement of the gangions — which drop from the mainline and hold the hook — from one day to the next.
“You’ve got to fish smarter,” explains Captain Dewey Hemilright.
Pelagic longlines drift near the surface of the water, can extend many kilometers, and have a radio buoy for tracking and recovery. Hundreds of the gangions or branch lines drop off each mainline. The lines roll off a rotating drum on the fishing vessel’s deck.
Despite fishermen’s efforts to avoid interactions, pilot whales may be injured while feeding on tuna already caught on longline gear. Hooks may cut the animals in the mouth or body.
A research database of pilot whales off Cape Hatteras shows many with healed scars returning to the established fishing zones. That leads Hemilright to ask how federal regulators define a “serious injury” to an animal — a factor in the Take Reduction Plan. Sometimes a hook may remain caught on a pilot whale. On rare occasions an animal may become tangled in gear.
“It can be very difficult and dangerous for the fishermen to dehook the whale,” explains Andrew Read of the Duke University Marine Laboratory. “Sometimes the fishermen have to cut the line, releasing the animal with a portion of line trailing.”
Efforts to completely disentangle the whales can be difficult for North Carolina’s pelagic fishing fleet that includes relatively small boats of about 40 to 45 feet in length.
“Pilot whales may weigh a couple tons — and may be thrashing about,” Read explains.
Thus, crews remove as much gear as possible from the entangled animal. Efforts are underway to develop better line cutters to increase safety for the fishermen and the pilot whales or other marine mammals that may get caught in gear.
This article was published in the Summer 2009 issue of Coastwatch.
For contact information and reprint requests, visit ncseagrant.ncsu.edu/coastwatch/contact/.