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UBC Theses and Dissertations

Climate change impacts on living marine resources in the Eastern Tropical Pacific Clarke, Tayler McLellan


The impacts of climate change on fish stocks are heightened in the tropics, where catch losses are projected to be three to four times the global average. Yet, there are large sub-regional variations in the drivers and magnitudes of shifting species distributions and their implications for fisheries. In this thesis, I aim to better understand the impacts of climate change on fisheries in the Eastern Tropical Pacific Ocean, from Mexico to Peru. First, I applied a species distribution modeling approach to project future impacts on species caught by the main fisheries in the region. Species are projected to shift towards the equator, seeking the more favorable, cooler habitats associated with the Humboldt and equatorial upwelling systems, as well as towards more oxygenated, inshore waters, away from the expanding oxygen minimum zones. Second, I developed and evaluated the performance of a Biogeographically derived Metabolic Index (BDMI). The BDMI can be generalized to assess the combined effects of warming and deoxygenation on the habitat viability of marine fishes and invertebrates. Thirdly, I applied two catch-based indicators derived from the BDMI to analyze the sensitivity of pelagic fisheries in the Eastern Tropical Pacific to warming and deoxygenation between 1970 and 2009. Temperature was the main factor driving oxygen limitation in pelagic catches. In contrast, when I applied these indices to the demersal community along the oxygen minimum zones off the Costa Rican Pacific coast, ambient oxygen was the main factor driving the responses of the exploited community, although species distributions were sensitive to changes in both temperature and oxygen. In both pelagic and demersal environments, I identified potential temperature and oxygen thresholds that separate different exploited communities with different sensitivities to changing temperature and oxygen levels. Overall, I conclude that warming and deoxygenation will likely impact fisheries resources in the region, revealing the importance of expanding our capability and credibility in projecting future changes. By modeling the mechanisms underlying the non-linear responses of biological communities to ocean warming and deoxygenation, the analytical approaches developed in this thesis can facilitate the detection, attribution and projection of climate impacts, including biogeographical shifts and three-dimensional habitat compression.

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