Skipper Stephen Rhoades of the Marilyn J (left), University of Alaska BLaST student Kate Hauch, Dr. Thomas Gordon (foreground), and Alaska Longline Fishermen’s Association program coordinator Dan Falvey (right) coordinate the release of hydrophone arrays for tracking sperm whales that strip fish from commercial fishing gear. (Photo Provided by Anna Wietelmann)
A unique alliance between fishermen and scientists has attracted attention and participation from international scientists.
A world-renowned marine mammal scientist from Scotland and his brother, an expert in underwater microphone technology, came to Sitka to test a new technique to locate sperm whales. The two, Dr. Jonathan Gordon of the Scottish Oceans Institute of St. Andrews and Thomas Gordon were in Sitka last month working with their new device. If successful, the technology would allow fishermen to identify the presence and location of sperm whales within 5 miles of their boat, allowing fishermen to more easily avoid sperm whales and reduce the chances of having whales take fish from their longline gear.
The sperm whale issue began as early as the 1980s, when longline fishermen approached Tory O’Connell, then a groundfish manager for the Alaska Department of Fish and Game, with reports of sperm whales feeding on sablefish (black cod) from longline gear. This behavior, known as depredation, is not only economically costly to the fishery but also potentially dangerous for the whales. Like garbage bears of the ocean, the whales are engaging in an unnatural behavior that increases chances of human conflict, like getting caught in gear.
In the 1990s interactions increased, Tory O’Connell, reached out to Jan Straley, University of Alaska Southeast (UAS) whale biologist and Linda Behnken and Dan Falvey of the Alaska Longline Fishermen’s Association (ALFA). With funding from the North Pacific Research Board they formed Southeast Alaska Sperm Whale Avoidance Project (SEASWAP) in 2003. SEASWAP hopes to understand the complex relationship between sperm whales and the longline fishery and ultimately provide recommendations to decrease or eliminate depredation. SEASWAP has since formed other collaborations, including Scripps Institution of Oceanography to work on deterrent methods.
“It is not common, still, after all these years for fishermen, scientists, and managers to work so closely and collaboratively together. Some of the best and innovative experiments we have tried and techniques we have in our toolkit are because of the knowledge of the fleet, they are just good at thinking through solutions. So this is kind of a rare and very rewarding partnership. The fleet has been very proactive in helping drive this research,” says O’Connell.
Now with funding from the Central Bering Sea Fishermen’s Association, Jonathan Gordon, one of the world’s leading sperm whale experts, is joining in the effort in sperm whale avoidance all the way from Scotland.
“It’s nice that the fishing industry came looking for answers,” reflects Jonathan Gordon on the partnership between fishermen and scientists. “I think Sitka is very good in that respect.”
Gordon and his brother, spent three weeks this June working with local fisherman Stephen Rhoades, skipper of the F/V Marilyn J, and Lauren Wild, a PhD student at the University of Alaska Fairbanks' School of Fisheries and Ocean Sciences. Lauren grew up in Sitka and has been a part of SEASWAP since 2009. In 2013 she received her master's degree in Marine Mammal Science from the University of St. Andrews in Scotland, where she worked with Jonathan Gordon on her dissertation, which focused on sperm whale acoustics.
“The way to study sperm whales is acoustics,’’ says Wild, who first joined SEASWAP as a research biologist and acoustic technician and is now looking at sperm whale diet and ecology for her PhD research. This is because “they are deep divers, hard to track [visually] really far offshore, and come up miles away. If they are diving, they are clicking.” Sperm whales, like bats, produce clicks to echolocate, or navigate by reflected sounds, during dives to depths where there is very little or no light. Rather than trying to spot sperm whales when they are at the surface, scientists find it more effective to record their clicks.
Last month, the team took two trips offshore, and two day-trips within the Sitka Sound, to test the equipment they have been developing for years.
The Gordons equipment, called a towed array, consists of a 200 meter long cable, ending in an oil-filled, plastic tube containing two underwater microphones, or hydrophones, one situated three meters in front of the other. The array is towed behind the fishing vessel. Unlike the use of a traditional hydrophone, which requires the vessel to be stopped while it is deployed, the towed array is meant to be used while fishermen are moving to provide real-time information.
The towed array relies on clicks produced by sperm whales to locate where they are. Sperm whales spend 75 percent of their dives, which typically last up to 60 minutes, producing clicks to navigate to locate prey. The two hydrophones pick up these incredibly powerful clicks. The device converts the clicks into electrical signals and sends that signal up the cable to be filtered and amplified. It is then run through a computer software called Pamguard, for analysis.
The computer program times the difference in arrival times of the sperm whale clicks between the two hydrophones and uses this to provide the user with a bearing for the whale. The program also uses the rate of change of the whale’s bearing to figure out how far away the sperm whale is.
The Gordons used their time in Sitka to work on some of the issues that stand in the way of widespread use by the longline fleet. “We still have more work to do, mostly with the details of how to make it more appropriate: to figure out a simpler power supply, and make the software interface more straightforward, ” says Jonathan. The ultimate goal is to have a product that any longline fisherman can take out and use themselves to tell where whales are and then avoid them.
“This will give fishermen a powerful tool to help them make informed decisions when on the fishing grounds,” remarks Dan Falvey, fisherman and project coordinator for ALFA. “When you’re out there now, you don’t know if there are whales in the area unless you see a spout. The towed array will tell you if there are whales within 5-6 miles of you and in which direction. If there are whales in the area and the fishermen know it, they can keep moving until they find a whale free area.”
The towed array is the most recent attempt at avoiding sperm whales. Other attempts have included acoustic decoys that play sounds mimicking the sound of boat engines, beads on longline gear meant to confuse the whale’s echolocation, and a reporting network where fishermen use texting devices to report whale locations and are given location of tagged whales to aid the fleet in avoiding whale interactions. For more information about SEASWAP, please visit www.seaswap.info.
(Photo Provided by Anna Wietelmann)
This article appeared in the "Daily Sitka Sentinel" on Tuesday, July 26, 2016. It was written by Sitka Sound Science Center Science Outreach Intern Anna Wietelmann. Wietelmann received her B.S. in Earth Systems from Stanford this Spring (2016) and is a M.S. candidate in Earth Systems at Stanford.