Southeast Alaska Sea Otters

We've been working on a sea otter project looking at the conflict between commercial fisheries and sea otters. In southern and southeast Alaska we're seeing increases in the sea otter population, actually fairly significant increases. So this is a growing population both in distribution and abundance. The issue was sort of brewing in my mind for a couple of years before Zach approached me about trying to tackle it from a research end. And primarily that was because Dungeness crabbers were coming and either talking to me or I listened to them testifying at a Shellfish Board of Fish meeting. Their concerns both for their bottom line but I think also for the resource because once they've seen otters in a bay for several years or even just one or two years, they won't fish there anymore because they're not catching any crab there anymore. They're worried that they're going to lose their income and they're also worried that because they're being forced into these smaller areas they're going to overly deplete that resource. Right now sea otters are competing directly for the California sea cucumbers, which are commercially harvested by divers as well as geoduck clams and red sea urchins, and the Dungeness crab fishery. The sea otters were extirpated by the commercial fur trade probably about the late 1800s and by 1911 when the International Fur Seal Treaty was put in place, sea otters were non-existent in southeast Alaska. Otters were reintroduced in the late 60s. A little over 400 otters were translocated. The populations were really insignificant as it related to competition with commercial fisheries for probably 20 plus years. But as these populations of otters got established, they got to the point where they could kind of grow rapidly in the way of numbers. And at the same time, commercial fisheries were being developed. We really started seeing the conflict between otters and fishermen probably in the early 90s. At that point, the otter population was at a level that it was impacting commercial fisheries. And so since that time, we've seen the otter population continue to grow as well as the participation and value of some of these commercial fisheries grow. We've seen several areas which have been closed to commercial fishing. And once those areas have been depleted of a couple of these resources, they've remained closed. Sea otters are kind of at the top of their food chain. And they're voracious predators. Because of that voracious appetite, they have the ability to kind of consume a lot in an area. So the classic paradigm is that where otters move in, they remove herbivores from the ecosystem. And that allows kelps to reestablish themselves. And some of these large canopy kelps, such as Macrocystis, those are important and very productive habitats, especially for early life histories of fish. We're kind of seeing in areas where otters are moving in, they're changing those ecosystems currently here. Areas that are going from a monoculture, sort of urchin barrens, for instance, kind of changing into a more diverse ecosystem. And that's great when we talk about ecosystems. But when we talk about commercial fisheries, that's not a good thing. That is precluding some of the existing fisheries from moving forward in southeast Alaska. These populations of otters, they haven't been followed well since they were reestablished. So the first thing we needed to do was just know how many otters were here. And once we established that, ongoing with those efforts to survey the otters, we also felt it was very important to look at the diet of sea otters. What are sea otters consuming? What proportion of their diet is these commercially important species? We're using high-powered telescopes to observe otters. Lucky for us, otters bring everything they eat to the surface. We're also recording the dive times and how many calories per unit effort an otter is consuming. Commercially important species are some of the most calorically rich and preferred prey of sea otters. The third sort of aspect of this research is to look at otters' movement at the edge of the range. We've established that otters are impacting these commercial fisheries. And so one of the things we wanted to do is look at otters and how otters were distributed and how their dispersal was from these sort of edge-of-the-range areas. And as otters move into new areas, areas they haven't been existing or established populations in yet, we were interested in what's going to happen here in the next year or two. So we've instrumented 30 otters in this area with VHF transmitters. And we're following those otters as they disperse from where we caught them. And the next step of the research is collecting foraging data from those animals. Right now we're working in Saginaw Bay. This bay has been inhabited by sea otters probably for, I would say, about seven or eight years now. And there's no longer a commercial dungeon-esque fishery in Saginaw Bay. And today we probably saw 100 to 125 otters in the bay. It looks like from some work we've done previously, they're mostly eating several species of clams and smaller crabs. We may be able to make some kind of a prediction for a commercial fisherman that says this is what you can guess is going to happen in the next 5, 10, 15 years in your fishery as we see this otter population change. The project itself is not going to be providing answers or recommendations for what to do. But we'll be providing information that will help decision makers, policy makers, community members, commercial fishermen make decisions about what to do in response, if anything.