The rocky shores of Prince of Wales, Alaska: intertidal ecology, abalone, and community sustainability

Abstract

Rocky, nearshore ecosystems are diverse and dynamic environments that function as the link between land and sea and provide important resources for people. In this two-part thesis, I first examined rocky intertidal ecological communities to better understand biotic and abiotic drivers in this system, and then I investigated the abundance of pinto abalone (Haliotis kamtschatkana), a key subsistence resource that local community members identified as the most important because of limited harvest and drastic declines. Pinto abalone are tied to Haida subsistence, culture, and spiritual identity and have been a traditional harvest species for the Haida people for millennia. Pinto abalone were harvested by non-Native fishermen through heavy commercial (1970-1996) and personal use harvest, causing a crash of the population. In the rocky intertidal I surveyed the upper and lower extents of major biobands, frequency of occurrence of sessile organisms, and abundance of mobile invertebrates across a vertical gradient at 18 sites near the west coast of Prince of Wales Island. A multivariate approach was used to identify the major drivers of rocky intertidal community composition and structure. Sea otter (Enhydra lutris) occupation time, average fetch, beach aspect, rugosity, and rock texture were all identified as influential forces for at least one tidal zone and/or biological metrics. Sea otters were not found to restructure the ecosystem, as they do in deeper kelp forest habitats. To assess the current viability of pinto abalone harvest, concerns about sustainability, and their ecological relationships, I partnered with local harvesters within the community of Hydaburg on Prince of Wales Island to combine Indigenous Knowledge about pinto abalone harvest with SCUBA surveys at historically productive traditional harvest sites. Only four (out of 17) of our shallow transects (2 x 20 m), which are within the depth range for traditional harvest methods, had legal-sized pinto abalone (max = 1 abalone). The traditional pinto abalone harvest fishery failed three out of four fishery recovery criteria that were examined. Fourteen out of eighteen sites did not have large (≥ 100 mm) pinto abalone, and pinto large abalone densities were below 0.1 abalone/m2 at all sites. All intermediate size classes of pinto abalone were represented within the fishery, but only 20% of large size classes were observed. Low pinto abalone abundance leads to concerns about traditional harvest viability and spawning failure and thus recruitment failure, for this density-dependent spawning species. In our generalized linear models, pinto abalone presence, density, and biomass were affected by sea urchin biomass. This baseline study of the current state of pinto abalone at traditional harvest sites bestows critical information to a community that depends on pinto abalone as a resource. The Hydaburg Cooperative Association, as a federally recognized Tribe, can use this information to make local management decisions, which include adjustments to harvest guidelines, implementation of sea otter management zones, and/or the establishment of pinto abalone restoration projects. Working with the Tribe and community members throughout the research process led to better science, applicable data, and took a step toward equity and reciprocity in the research processes.