1 year ago




OCEAN CHRONICLES In Search of Whales, Part 2: Alaska's Killer Whales Photo Josh McInnes JOSH MCINNES We had missed the killer whales by half a day. We scanned for hours hoping to get a glimpse of a tall black dorsal fin cutting the surface of the water. Our main goal during this expedition was to study the behaviour and distribution of killer whales in Southeast Alaska, home to different ecotypes of killer whales that frequent the waters of the Pacific Northwest. Three ecotypes have been classified based on acoustics, morphology, genetics, and diet. Being apex predators, diet is crucial, and shapes all other aspects of their ecology. The resident killer whales focus on fish, while transients specialize in mammals. The poorly known offshore ecotype has been known to forage for elasmobranchs and other species of fish. The three ecotypes make up populations and subpopulations along the coast. The resident killer whales are found in three distinct subpopulations, with very little overlap. The southern resident killer whale subpopulation is centered off Southern Vancouver Island and Puget Sound, but has also been sighted as far south as Monterey Bay, California. The northern resident community is often encountered in the protected waters of Northeastern Vancouver Island, but is also sighted as far north as Southeast Alaska. The largest resident community is the Alaskan subpopulation, which overlaps slightly with the northern residents. Pods within this subpopulation range widely from the protected waters of Southeast Alaska to the remote and unpredictable coastal waters of the Gulf of Alaska. The transient ecotype is also distinguished by three major subpopulations along the coast. The largest known subpopulation frequents the waters from Northern California to Southeast Alaska, and is known as the west coast transients. Further north in Prince William Sound, two sympatric smaller subpopulations have been identified: the Gulf of Alaska and AT1, or Chugach, transients. The Gulf of Alaska transients are widely dispersed across the Gulf of Alaska and have only been encountered a few times in Southeast Alaska. The small AT1 subpopulation is on the verge of extinction, with seven remaining animals. They met their demise as a direct result of human exploitation of natural resources. When first studied, the population contained 22 animals, and subsequently dropped to 13 animals a few months after the infamous Exxon Valdez oil spill of March 1989. It was the last day of our journey. We had encountered many amazing organisms, and our hopes of finding killer whales remained high. We were traveling to a NORTH ISLAND COMPASS | ISSUE 8

location known as Endicott Arm, a place frequented by transient killer whales. Endicott Arm is a fjord spanning approximately 45km, ending at a spectacular calving glacier known as Dawes Glacier. Endicott Arm is also home to an astonishing number of harbour seals, which haul out on ice floes to give birth in the months of May and June. The harbour seal population in Southeast Alaska has declined in recent times. This decline is poorly understood, but lack of food and a changing ecosystem have been considered major factors. The further we traveled, the more concentrated the ice floes became. Towering blue and multi-shaped icebergs passed us, each one unique in its natural splendour. The ice became so thick that Jeffrey had to go outside to spot icebergs, while Christine navigated the vessel. The closer we got to the glacier, the more harbour seals we counted. Numerous pups were huddled close to their mothers, while others swam close to their ice floe. As we approached Dawes Glacier, we could hear small pockets of ice explode and drop to the water in what are called snowballs. We waited in anticipation, as each crack of ice could lead to a successful calving. All of a sudden a thunderous sound emanated from the glacier, and a 200 metre chunk of ice cascaded to the water’s edge, sending a large wave towards us. As we departed the glacier and made our way towards the entrance of Endicott Arm, I heard Christine from the galley yell, “Killer whales!” We all jumped up and headed outside to pinpoint their position. In the distance four transients had quietly entered a small bay known as Little Endicott. We slowly motored in to get a better look. We recognized them as the T124s, a family group we often encountered off Vancouver Island. They had just killed a harbour seal and had begun traveling back towards the glacier. The whales navigated the ice floes with precision, looking for another seal. As I watched and studied them, I realized why I became so interested in killer whales. I have always been interested in their cultural transmission of foraging behaviour, and how this behaviour is influenced by geographical distribution. Questions Photos Josh McInnes like: How do transients passively communicate while foraging around ice floes in glacial turbid water? How do they pick up the sounds of prey while foraging in an environment surrounded by ambient noise produced by river runoff, or by the differential expansion as liquid water and ice meet? How often do transients visit this region, and are their special foraging methods employed between and within groups geographically? As we watched the whales depart, I pondered these questions. Will I ever know the answers? I hope with future expeditions that we will have the opportunity to learn more about this vast region of Alaska, and the whales that call it home. Open Year Round Full Service RV & Camp Sites On-site Marina Boat/Kayak Launches Whale Watching Fish Charters On Site Trailer Rental Oceanfront Property Spectacular Sunsets! Family & Pet Friendly LOCATED ON-ROUTE TO TELEGRAPH COVE PO BOX 1090 | PORT MCNEILL, BC | V0N2R0 1.888.956.4117 ALDERBAYRESORT@GMAIL.COM WWW.NORTHISLANDCOMPASS.CA | 7 WWW.ALDERBAYRESORT.COM

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