Date

Spring 2020

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Applied Environmental Science

Abstract

Oceans display physical variability over a range of temporal and spatial scales, influencing factors such as larval dispersal, nutrient availability, species migration, and biodiversity. Such variability is vulnerable to the effects of climate change. Larvae and juveniles are particularly susceptible to changes in ocean variability, and changes in the early life stages of species populations ultimately impacts the adult stages. Physical consequences stemming from climate driven variability, including a loss of key prey species and changes in depth distributions of vulnerable fish species, could ultimately impact ecosystem services and threaten human food security and fisheries. The deep sea benthopelagic groundfish play significant roles in biogeochemical and ecological processes on a global scale. Macrourids, the most common benthopelagic fish in the deep sea, are important benthic and midwater predators; making it critical to understand changes in their population structures over time. Macrourid larvae reside in surface waters, where they are more vulnerable to climate driven variability. Merluccius productus (M. productus) is a commercially important benthopelagic groundfish species with a life history similar to Macrourids. The combination of surface waters exhibiting more changes in physical variability compared to the deep sea and the vulnerability of larvae to oceanographic variability makes observing these benthopelagic species particularly important for understanding the full-depth interactions and climate-related changes. This project focuses on studying correlations between changes in the life stages of Macrourid species' and M. productus' populations over time in relation to changes in climate and surface ocean conditions. Four research questions are addressed; Q1 & Q2) Has groundfish (specifically Macrourid spp. (Q1) and M. productus (Q2)) population structure changed over time in relation to changing climate and surface-ocean conditions?; and Q3 & Q4) Has the depth range of groundfish species (specifically Macrourid spp. (Q3) and M. productus (Q4)) changed over time with changing climate and surface-ocean conditions? With increasing changes in climate and surface-ocean conditions over time, there is a significant change in both Macrourid species' population structure and M. productus population structure over time (Q1 and Q2). With increasing changes in climate and surface-ocean conditions over time, there is no significant change in M. productus' depth distribution over time (Q4). Regarding potential changes in Macrourid species' depth distributions, Q3 couldn't be answered due to insufficient data. This study increases our understanding of how potential impacts of changing climate and surface-ocean conditions on M. productus' population structure and depth distribution could affect Macrourid populations. Findings also provide valuable insight for: 1) predicting and managing consequences of climate change and 2) management of coastal and marine resources and fisheries in the future.

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