Pinto abalone (Haliotis kamtschatkana) populations in Alaska have faced numerous ecological pressures, including the extirpation of Northern sea otters (Enhydra lutris kenyoni) due to the international maritime fur trade, the establishment and later emergency closure of a commercial fishery, the repatriation of sea otters, and ongoing subsistence harvest. Abalone are significant to the region for both ecological and cultural reasons. However, data deficiencies hinder the proper understanding and management of the species across its northernmost range, as no comprehensive surveys of pinto abalone across Southeast Alaska exist. This body of work aims to 1) assess the lasting impacts of fisheries and sea otters on present-day population demographics, 2) explore variations in abalone populations and recruitment and factors promoting recruitment across Southeast Alaska, and 3) assess the indirect and direct effects of repatriating sea otters on abalone populations. In Chapter 1, we assessed the impacts of fisheries and sea otters on current (2016, 2019) population demographics through comparisons of recent resurveys with historical datasets in areas both with and without sea otters. Compared to historical surveys, locations with repatriated sea otters and historically intensive fishery landings had the most significant reductions in abundance and size frequencies. Yet, locations with moderate harvest and no established sea otter populations remained similar to historical surveys. Through a spatially nested design in Chapter 2, we determined the present-day (2018, 2019) population metrics important to management (i.e., abalone densities, recruitment, size structure) and calculated reproductive capacities (i.e., egg mass) and fertilization potential (i.e., aggregation metrics) across Southeast Alaska. We identified distinctly different abalone populations across sites and regions, including Sitka, Prince of Wales Island, and Dixon Entrance, all showing evidence of visible recruitment. We determined adult abalone critical densities of (0.2/m2) and nearest neighbor distances of (0.2m), beyond which there was a minimal increased benefit of fertilization potential. Finally, with established ecological patterns following sea otter re-establishment, modeled data, and local expertise on sea otters, along with dive surveys of urchins, algal cover, and abalone (see Chapter 3), we identified the indirect benefits of moderate sea otter influence. We found abalone persist with and may likely indirectly benefit from the presence of sea otter populations through their consumption of herbivore competitors like sea urchins, whereby locations where otters remained absent had higher urchin biomasses and lower abalone densities (i.e., Dixon Entrance) than locations with long-established sea otter populations (i.e., Sitka). These findings provide the most comprehensive review of pinto abalone populations throughout Southeast Alaska and suggest effective abalone management must consider complex indirect interactions with sea otters and direct impacts of human harvest at smaller localized scales.
