UC Santa Barbara

As the global human population grows and the middle class widens, resources are becoming increasingly scarce and today’s highly interconnected food systems require complex solutions. Freshwater supplies and land to expand agriculture is limited, as is the capacity to assimilate pollution from excess nutrients and greenhouse gas emissions. Since the 1970s fisheries catches have stagnated. Meanwhile, aquaculture has rushed to meet growing seafood demand and has become one of the world’s fastest growing food sectors. In order to avoid competition for land and water resources, aquaculture is increasingly moving offshore, where it is encountering new conflicts with capture fisheries. Maintaining healthy wild capture fisheries while sustainably expanding aquaculture offshore will be important to ensuring diverse and robust seafood supply into the future, so understanding the interactions between these coupled sectors will be important to their responsible co-management. This work seeks to understand ways to sustainably develop aquaculture into an increasingly resource scarce and uncertain future. The work here highlights some of the most pressing issues is aquaculture development and identifies pathways to more efficient food production and co-management.

A primary environmental burden of aquaculture comes from their feed, which are comprised of capture fisheries products and crops that could be used directly for human consumption and can have high environmental footprints associated with them. Novel feed ingredients have been developed to reduce reliance on these human-food inputs, namely, single cell proteins (SCPs), and may also decrease the environmental impacts of aquaculture feeds. SCPs are protein-rich non-human food inputs that can reproduce quickly and efficiently. My first chapter considers SCP ingredients in compound aquaculture feeds and compares the environmental footprint of replacing conventional ingredients with these emerging inputs. This work focuses on salmon feeds produced in Norway, the world’s largest producer of farmed salmon and leader in aquaculture development, to be able to more fully investigate the tradeoffs and nuances of the feed production system. The second chapter places these ingredients in the context of global feeds by considering the potential role of these ingredients in animal production more broadly. Specifically, I project meat consumption into the future and compare the relative importance of shifting human versus animal diets in the overall greenhouse gas impacts of meat production.

By placing aquaculture in marine environments, farms initiate additional interactions with wild species and capture fisheries. Chapter three simulates several impacts of ocean farms on wild capture fisheries. I use a theoretical bioeconomic model to predict how changes to movement and access to wild species at a farm might affect population and fishing dynamics in order to inform siting and co-management of these highly connected systems. This dissertation incorporates multi- and interdisciplinary approaches to address some of today's biggest food production challenges, calling upon industrial and population ecology, economics, and statistical and theoretical modeling methods.

This work finds that novel feed inputs -- particularly single cell protein meals -- can decrease environmental impacts of aquaculture feeds, of particular note are single cell yeast protein meals. While bacteria meals can decrease demands for land and impacts on eutrophication, their potential for further environmental benefits are less certain. In the larger context of global livestock production, yeast protein meals can decrease impacts of meat production, and both human diets and inputs to feeds can help decrease impacts of meat production into the future. In the third chapter I conclude that ocean farms can benefit wild populations and fisheries catches when stocks are overfished by allowing populations to recover through de facto protection within the boundaries of the farm. Smaller farms can provide more benefits to fisheries compared to large contiguous farms of the same size due to increased access to protected and recovered stocks, although strong farm-level management is important to ensure neutral or positive direct impacts to wild populations to optimize benefits from farms. These results are geared to inform strategic planning and management of aquaculture and some of the key industries with which it interacts to guide more sustainable food systems into the future.