Marine plastic pollution, particularly from abandoned, lost, or discarded fishing gear (ALDFG), has become a pressing environmental and governance challenge in global fisheries. Ghost fishing, where lost gear continues to capture fish and other marine organisms, leads to unnecessary mortality, stock depletion, habitat damage, and economic losses. Despite growing awareness, policy responses remain fragmented, and there is limited understanding of the ecological, economic, and behavioral dynamics driving ALDFG. Effective mitigation demands both improved regulatory instruments and a deeper grasp of fishers' incentives and barriers to change.
This thesis addresses these challenges through four interconnected studies. The first paper conducts a systematic review and meta-analysis, identifying critical gaps in the ALDFG literature, including the lack of economic assessments and limited integration of ecosystem services. The second paper develops a dynamic bioeconomic model of ghost fishing that integrates stock dynamics, gear loss, and vessel behavior in a competitive, restricted-access setting. The model is calibrated to the Norwegian snow crab fishery, where gear losses are frequent and stakes are high. Results suggest that the current retrieval program is not economically efficient under baseline conditions, while a harvest tax outperforms a quota regime by improving effort allocation among heterogeneous vessels. These findings highlight the limitations of top-down regulatory approaches and motivate the shift in Papers 3 and 4 toward understanding bottom-up behavioral responses, particularly voluntary participation in preventive strategies.
Papers 3 and 4 focus on the voluntary adoption of biodegradable fishing gear as a preventive strategy. Paper 3 reveals that behavioral factors, such as peer influence and environmental concern, play a stronger role in shaping adoption intentions than economic incentives alone. Paper 4 shows that fishers adopt biodegradable gear unconditionally when it performs as well as conventional gear. As efficiency declines, adoption becomes conditional on others adopting, highlighting the role of strategic concerns in achieving widespread uptake. Together, these studies offer a comprehensive view of the ALDFG problem and propose pathways for more effective and socially informed fisheries governance.
