Abstract

Coral-reef fisheries have provided food security and recreation for societies across the tropics for countless generations, and are also estimated to provide nearly $6 billion USD in net benefits to the world annually while supporting the livelihood of over 6 million fishers and their families. Yet, unsustainable fisheries regimes with ensuing impacts to coral-reefs and societies that depend on them have been reported over the last decades across most tropical regions. Alongside, management frameworks continue to struggle to ensure sustainable fishing regimes in the face of limited evidence-based guidance and the prevalent context of limited capacity and resources. This thesis aimed to advance on the field of small-scale multi-species fisheries by enhancing our understanding of exploitation and stock dynamics, the drivers behind those dynamics, and potential novel management paths towards sustainable fishing regimes. Within, it focuses on poorly understood coral-reef fisheries and on the drivers and progressive dynamics associated to increased commercialization of those fisheries, ensuing localized depletions and fisheries expansions, and inevitable impacts to stocks and societies. We used three islands in Micronesia (western tropical Pacific) with extensive multi-species coral-reef fisheries that are dominated by nighttime spearfishing as case studies to test our hypothesis. The islands presented useful gradient of levels of fishing pressure and reef-fish trade networks within and across. Our studies targeted multispecies fisheries that generally included over 100 species at any given island, but specific analyses focused on the most dominant species that had more data available. Those were mostly members of parrotfish, surgeonfish, grouper, emperor, snapper, and rabbitfish families. Previously unexplored records of 13 years of reef-fish exports from Chuuk (Federated States of Micronesia) to Guam (USA) were compiled and analyzed to explore how environmental and socioeconomic factors combined, and evolved, to drive export patterns over time (Chapter 2). Extensive commercial landings records and coupled fisher interviews that were collected over one year and an existing limited subsistence landings datasets from Chuuk served to assess impacts on stocks of the export-driven commercial fisheries expansions (Chapter 3). Lastly existing unique historical and snapshot landings datasets from Guam (USA) and the Commonwealth of the Northern Mariana Islands (USA) were used to assess i) potential development of landings variability dynamics and masking effects associated to fisheries expansions (Chapter 4), and ii) variability of species responses to fishing pressure and potential implications for restructuring of fisheries (Chapter 5). Analysis of export records highlighted how coral-reef fisheries are increasingly becoming subject to complex exogenous market drivers that may easily be hidden and out of the control of local fisheries managers and stakeholders, in this case changes on wellfare programs in Guam coupled with global rises on crude prices that drove a boom-and-bust cycle for exports between Chuuk and Guam. Chuuk extensive landings datasets provide evidences regarding disproportionate impacts on stocks and ecosystems of commercial fisheries (which are fueled by growing trade networks) as compared with subsistence counterparts, as highlighted by compromised status of species disproportionally targeted by commercially fishers that were generally more vulnerable, and evidence of growing depletions on areas more accessible to markets. Analysis of CNMI datasets highlighted how expansions of fisheries footprints following localized depletions at more accessible stocks provided for maintained supply to markets over 11 years (albeit with increasing variability and changes in catch composition), which could mask ongoing localized depletions and disproportionally impact subsistence fishers that cannot access less exploited remote areas. Finally, combined CNMI and Guam datasets revealed how regardless of fisheries expansions, fisheries are bound to be impacted as evidenced by signs of fishing ‘down’ and ‘across’ food webs and species replacements as more resilient species that often showed size-truncated landings increasingly substituted others with slower growth-rates and weaker density-dependent responses that diminished or even disappeared from landings. Cumulatively, ongoing complex commercial coral-reef fisheries footprint expansion dynamics across multiple geographical scales can have profound and long-lasting implications for targeted stocks, the fisheries sector that depends on them, the ecosystems they sustain, and ultimately the societies that rely on them for food security and other ecosystem services, suggesting that deep re-evaluations of coral-reef fisheries commercialization tradeoffs are warranted. Further research areas and considerations for future evaluations of coral-reef fisheries management paradigms such as reconsideration of approaches for defining spatial and taxonomic management units, and re-evaluation of underlying assumption regarding compensatory density dependence responses to fishing and associated stock assessment frameworks and size-based management policy approaches may improve management of such complex multi-species fisheries.

Document Type

Thesis

Publication Date

2021-01-01

DOI

10.24382/802

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