Coastal Indigenous Peoples worldwide have relied on fish and other marine resources for millennia, and continue to do so despite recent degradation of ocean systems. Their traditional ecological knowledge, comprised of experiences, observations, beliefs, and lifeways, is relevant for modern marine management and conservation. This thesis explores the utility of traditional and local ecological knowledge for extending an understanding of changes over time for places or periods in which scientific data are unavailable. This thesis had three goals: 1) undertake research that is collaborative and inclusive, and that addresses priorities established by participating First Nations; 2) contribute to fisheries management and conservation recommendations by focusing on a species of cultural importance and exploring the applications of traditional and local ecological knowledge to species-level understandings; and 3) contribute a marine social-ecological case study that investigates the use of traditional and local ecological knowledge to understand change over time and provides appropriate context. Two main objectives allowed me to accomplish my goals: 1) demonstrate the application of traditional and local ecological knowledge to establish historical baselines that extend farther back in time than scientific surveys, and investigate reasons for changes, and 2) investigate the utility of a social-ecological trap framework in assessing impacts to a social-ecological system and identifying ways to escape such a trap. My case study occurred in collaboration with four First Nations (as many Indigenous Peoples of Canada are called) on the Central Coast of British Columbia, Canada. My methods included semi-structured interviews with knowledge holders to examine traditional and local ecological knowledge of a culturally and economically important species, Yelloweye rockfish (Sebastes ruberrimus). In this study, I interviewed First Nations fishers and Elders (n=43), asking about: observed changes to the body sizes (length) and abundance of this species over the last ~60 years, the factors driving these changes, stewardship principles or traditional management strategies, concerns for marine resources, and perceived opportunities for cultural revitalization. I then quantified the interview participants’ current and historical estimates of size and abundance, compared interview data to current biological survey data, and qualitatively analyzed responses regarding stewardship, culture, perceived threats, and cultural solutions. I utilized the framework of a social-ecological trap to analyze responses about stewardship, traditional stories or management, and threats to culture, selecting illustrative quotes to contextualize the lived experiences of participants. Overwhelmingly, respondents had observed a decrease in Yelloweye rockfish body sizes since the 1980s. Median historical length observed by participants was nearly twice the modern length. Participants reported substantial decrease in Yelloweye rockfish abundance since the 1980s, and most stated that this change was evident in the early 2000s. Sizes of modern Yelloweye rockfish estimated by participants resembled measurements from ecological data recorded concurrently at the study region. Thus, my study extends baseline historical data of Yelloweye rockfish reliably by about 50 years. Questions about traditional stories and culture revealed the presence of a social-ecological trap created and reinforced by the interplay between species decline and colonization (e.g. the residential schooling system). When asked about traditional management or stewardship practices, only one participant could remember specific traditional stories about Yelloweye rockfish, though all participants expressed adherence to the stewardship principles of taking only what is needed and respecting all life. Though participants expressed concern about the muting of traditional ecological knowledge, culture, and language, they also highlighted key ways towards revitalization and Indigenous resurgence. The ubiquitous presence of stewardship principles suggests there are ways beyond the social trap: participants described on-going cultural revitalization efforts, recovery of depleted species and ecosystems, and the reassertion of Indigenous management rights as ways to overcome problems inherent to the social-ecological trap. My research adds to a growing body of literature that supports the use of traditional and local ecological knowledge in marine management and conservation science. Adding to this literature, my work suggests the significant value of traditional and local ecological knowledge for filling gaps in historical scientific data or in data-poor regions, and highlights the importance of appropriately contextualizing Indigenous knowledge. To overcome the social-ecological trap of knowledge loss and to achieve informed marine management, reassertion of Indigenous management rights and application of traditional management strategies to modern fisheries management is vital. / Graduate / 0326 / 0768 / 0416 / eckertleckert@gmail.com