Award: OCE-1600049

After sea otters were extirpated from Southeast Alaska during the 18th and 19th Century fur trade, approximately 400 sea otters were translocated to the region in the 1960s. Now, the population is increasing and expanding, or recolonizing, into its historical range. This provides a natural experiment for assessing how this keystone species and apex predator shapes its environment. While some impacts may be positive (e.g., increase in kelp forests), others may be negative (e.g., depredation on important commercial and subsistence resources). The aim of this collaborative project was to examine how the recovery of sea otters in Southeast Alaska affects nearshore marine ecosystems, provides ecosystem services, and affects community sustainability. Our objectives were to: 1) analyze the impact of sea otter recolonization on surface canopy kelp, 2) assess sea otter foraging ecology with respect to diet composition and nutritional intake, and 3) examine tourists? marine wildlife tour preferences. For our first objective, we combined a recently published sea otter population model with a novel spatial time series of kelp canopy dynamics determined from satellite imagery to investigate if increases in sub-regional sea otter population were associated with the expansion of kelp forest canopies across three decades. While there has been significant work relating the presence or absence of sea otters to the abundance of kelp over the past 50 years, these studies have been performed on local scales, usually by comparing sites with varying sea otter populations. Here, we used continuous spatiotemporal data over regional scales to establish that this pattern holds across areas of 1000?s of square kilometers. Specifically, we found that sub-regions of Southeast Alaska where populations of reintroduced sea otters increased through time showed large increases in new kelp occupied area, while areas without sea otter population growth showed little increase in new kelp occupied area. Furthermore, we found that the timing of the greatest increases in new kelp occupied area was associated with the timing of sea otter population growth. For our second objective, we found that sea otters inhabiting the western side of Prince of Wales Island and the surrounding islands ate a high proportion of clams with crabs, sea cucumbers, sea stars, and sea urchins as supplementary prey. At a regional level, sea otters did not significantly shift their diets by season or location, but there was strong individual-level variation. Sea otters seasonally increased consumption of some prey when the prey was highest in lipid and overall caloric content. Sea otters switched prey types when the prey was more energetically valuable. For our third objective, we administered a willingness to pay (WTP) survey to measure preferences for viewing sea otters on marine tours compared to other charismatic megafauna (humpback whales and killer whales). Our results revealed that WTP to see sea otters was much higher than WTP to see humpback whales. For example, WTP for a 50% chance of seeing sea otters was approximately $160, whereas WTP for a 50% chance of seeing humpback whales was approximately $50. Our collective results will help to inform local communities in Southeast Alaska about the projected impacts and potential benefits of sea otter recolonization. Taken together, this knowledge can aid in more effective ecosystem-based management practices and help communities to better co-exist with this apex predator. First, our results showing increases in surface canopy kelp as sea otters recolonized portions of Southeast Alaska provide evidence of the ecosystem benefits of sea otters. Kelp forests are critical components of healthy ecosystems, providing habitat for fish and invertebrates, and providing ecosystem services such as carbon sequestration and mitigation of shoreline erosion. Second, our results on sea otter diet can help to predict potential impacts of the expanding sea otter population on subsistence and commercial shellfish resources. Such knowledge can aid in development of effective co-management strategies for sea otters in Southeast Alaska. Finally, our WTP results showed that sea otters hold a high value in Alaskan marine tourism, even more so than the widely popularized humpback whales. These results will be important in informing tourist managers and operators within Alaska?s burgeoning tourism industry. These results also demonstrate the non-consumptive value of sea otters. This is important in regions such as Southeast Alaska that are experiencing human-wildlife conflict. We shared our progress and results widely throughout the study period, presenting more than 25 scientific and public talks in the US, Canada, and Norway, and publishing six peer-reviewed papers. There were also numerous training and professional development accomplishments. An undergraduate working on the project earned her BS and is now working for NOAA. The MS student graduated from the University of Alaska Fairbanks and is now employed as a Biologist at the US Geological Survey. The postdoctoral scholar is now an Assistant Scientist at the Woods Hole Oceanographic Institution. The PI and Co-PI both received tenure and promotion. Last Modified: 11/28/2022 Submitted by: Heidi C Pearson