Everyone has heard of the huge tides in the Bay of Fundy (Nova Scotia), but not everyone outside Alaska may have heard that Cook Inlet has the 4th highest tidal range in the world—30.3 ft (9.24 meters)! Most of my previous field work has been in the Aleutian Islands and Bering Sea, or far out at sea in the Pacific Ocean, where we didn’t really have to think about the tides that much. Here in Anchorage, for us everything revolves around the tides. In fact, we are only here right now because for the next week we have minus tides (really low tides) in the middle of the day, which works out best for us (something we learned from Tamara, our project partner who we introduced in the first installment of this blog).
During a minus tide, the mud flats on the Susitna Delta go dry, and the whales have to retreat to deeper water, where they tend to line up right along the edge of the mud flat. That makes them relatively easy to find, we don’t need to worry so much about running aground, and they tend to be bunched up in bigger groups, which we hope will help us get aerial photographs of more whales. Plus, by working the low tides, even if we go aground and get stuck, we know the tide will be coming back in soon to re-float us.
I have been to Anchorage many times before and spent a lot of time here, but I had never been down to the boat ramp by Ship Creek before, even though it is just a mud ball’s throw from downtown. In most of Cook Inlet, especially the upper Inlet, there is so much glacial silt in the water that we can barely see through it at all. It’s about the color of a double tall latte. Cook Inlet is really beautiful at high tide, but all that silt and mud can be pretty messy looking at low tide. Still, it was great to see all the urban fishermen in Ship Creek putting food on the table—the silvers (coho) are running now and we saw lots being landed on the muddy banks of the creek.
My first look at the ramp (the only one in the upper Inlet) at low tide was a little scary—a 70-meter-long dock sitting on the ground. And on further inspection, some really gooey looking mud on the ramp that looked like it could swallow a truck. Dave and Tamara had warned us we needed somewhere between 12-15 feet of water to safely launch the boat at the ramp. It would be easier to dock the boat at a marina rather than have to use the ramp everyday, but the tides, winds, and currents can be so severe here there are no marinas for small boats. So every day we work on the water, we have to get the boat in before the tide goes out too far, and once we are out, we can’t come back for over 6 hours, so we are stuck out there.
We developed the “Justin rule”—the water has to be to the 5th pole in on the dock at the far end before we can launch or retrieve; that way we know we have enough water to get over the mud bar off the end of the dock, and the water is far enough up the ramp where our truck won’t get stuck, or worse. Our first day was a little intimidating—it coincided with a salmon opener, so lots of setnetters were launching their fishing boats to get out, and, of course, they have done it hundreds of times and make it look easy. But so far so good; we haven’t had any drama at the boat ramp, and we hope it stays that way!
Meet the Blogger
Paul joined the Lab’s Cetacean Assessment and Ecology Program in 1996, after completing a Ph.D. at Scripps Institution of Oceanography, and a NRC Postdoctoral Fellowship at the Southwest Fisheries Science Center.
He has conducted killer whale research in the Aleutian Islands since 2001, and recently took over as head of Cook Inlet Beluga Whale research for the Lab.