Fishermen and Sperm Whales, the Challenges of Outmaneuvering Savvy Cetaceans


This past summer, AWF partnered with SEASWAP - a unique collaboration between commercial fishermen, scientists, and fisheries managers united in an effort to address the issue of sperm whale depredation on commercial long-line fisheries gear.  Sperm whales have learned to take sablefish off commercial fishing gear (i.e., 'depredate') in Alaska. This behavior is risky for whales and fishermen and results in economic loss in catch. The goal of SEASWAP is to understand the complex relationship between sperm whales and fishermen and to recommend strategies to reduce these interactions.

SAVVY CETACEANS OR BRAZEN THIEVES? - For the last decade, sperm whales have been traveling to the inside waters of Southeast Alaska to steal sablefish from commercial long-line fishermen.  The ~15 m whales find the boats by the sounds of their engines and then wait at the surface until the fishermen begin hauling their gear, at which point the animals dive below the surface and start stripping the lines clean as they're brought up off the bottom.

DEEP DIVERS - Sperm whales are among the deepest and longest diving air-breathers on the planet.  Although they can dive for over two hours and to depths of several kilometers, those in the inside waters of Southeast Alaska typically dive for 'only' about 40 minutes.  It remains unclear what, if anything, the sperm whales in our area are feeding on during those dives...aside from fishermens' catches!

TELLTALE BLOW - Sperm whales are unique in having a blowhole that is set both forward and to the left of their head, making their angled 'blows' fairly easy to distinguish from the tall bushy blows of humpbacks.  Once the binoculars are out, their low, rounded dorsal fin and the 'knuckles' on their tail stock are also giveaways.

TELLTALE BLOW - Sperm whales are unique in having a blowhole that is set both forward and to the left of their head, making their angled 'blows' fairly easy to distinguish from the tall bushy blows of humpbacks.  Once the binoculars are out, their low, rounded dorsal fin and the 'knuckles' on their tail stock are also giveaways.

Sperm whales can be challenging to work with as they spend so much of their time under water.  Fortunately for us, they navigate and find food by producing audible clicks and listening for their echos as they bounce off objects in front of them (called 'echolocation'), and these clicks can be heard for miles.  For most of July and August, we established a series of hydrophone stations to listen for echolocating whales and establish when they first arrived in the area. 

Commercial long-line fishermen are also integral to the project as their 'at-sea' reports of whale encounters help us zero-in on where the whales are actively feeding.  The economic impact from these whales can be substantial, so many fishermen - like the crew of the FV Republic - are more than happy to help out in an effort to find an amenable solution to this growing problem.

TEAM EFFORT - The SEASWAP (SouthEast Alaska Sperm Whale Avoidance Program) project requires a team of researchers with multiple vessels.  Taggers, dedicated observers, and data recorders operate on the vessel Nepenthe, while others collect skin samples and use directional hydrophones to locate diving whales from a second vessel.  

TEAM EFFORT - The SEASWAP (SouthEast Alaska Sperm Whale Avoidance Program) project requires a team of researchers with multiple vessels.  Taggers, dedicated observers, and data recorders operate on the vessel Nepenthe, while others collect skin samples and use directional hydrophones to locate diving whales from a second vessel.  

A tiny satellite tag (situated just in front of the dorsal fin on sperm whale 'GOA-091') allows us to track the movements of whales that are known long-line 'depredators'.  The data from these tags can help us better understand their behavioral and habitat use patterns.  But equally, they can alert fishermen to the whereabouts of these animals so they can more easily avoid them when setting their fishing gear.

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