Governance Relevant Insights on Harvesting in the Mesopelagic Zone

Governance Relevant Insights on Harvesting in the Mesopelagic Zone

van Deelen, Julie (TU Delft Technology, Policy and Management)

Kwakkel, J.H. (mentor)
Nikolic, I. (graduation committee)
Auping, W.L. (graduation committee)
Elsler, Laura (graduation committee)

Delft University of Technology

Engineering and Policy Analysis

2021-08-24

With the population growing and countries becoming more affluent, diets shift. These global dietary shifts contribute greatly to increasing greenhouse gas emissions because of their higher carbon and water intensities. This development is problematic considering both the growth in our global economy as well as our population. It is therefore crucial to find ways to reduce the impact of food systems. The mesopelagic zone in the ocean has recently been found to host a vaster source of biomass than expected, however, designing harvesting policies poses a deep uncertain issue. The mesopelagic zone promises a new source for the human food supply chain, especially serving as fish meal for aquaculture. Aquaculture is currently the worlds’ fastest growing food sector. However, unlocking the potential of the mesopelagic zone has challenges. The working of the mesopelagic zone and its ecosystem are still vastly unknown, as is the magnitude and variety of impacts harvesting might have on this. Moreover, the zone is located at a location beyond national legislation and still lacks overarching regulation. To acknowledge this research gap, this study focuses on how robust decision making methods can support decision making on harvesting in the mesopelagic system. This is done by analysing the current governance arena, the working of the mespelagic zone, and finally applying these findings to a System Dynamics model and performing Many-Objective Robust Decision Making (MORDM). Ultimately, to understand possible mesopelagic futures and thus gain governance relevant insights on harvesting in the mesopelagic zone. Exploring the model behaviour over a variability of plausible futures demonstrated that several uncertainties have a crucial impact on the mesopelagic system's best and worst case behaviour. It seems that profitability of mesopelagic harvesting relative to regular fishing is the most prominent indicator for collapses of the mesopelagic biomass. Additionally, factors concerning low food availability seem to be strongly linked to biomass collapse and vice versa. Moreover, reproductive parameters (e.g., a high female fraction of the biomass) as well as a high ratio of myctophidea to Maurolicus muerelli positively influenced the magnitude of food provision. Furthermore, other noteworthy findings are that an optimal harvesting quota seemed to act as a balancing tool for profitability. Additionally, exploration of the uncertainty space clarified which uncertainties have the strongest influence when no harvesting limits are in place. The two most influential uncertainties are the profitability of mesopelagic fish versus regular fish and the type of risk reward mechanism. This finding reduces the uncertainty space for decision makers by clarifying which indicators to focus on and which uncertainties might not even be relevant to consider for decision making. Moreover, it can be concluded that by harvesting according to the selected policies, the atmospheric carbon levels in 2100 would rise significantly enough to cause added pressure on the climate. This strengthens the call for considering climate change as well as biomass conservation when thinking about mesopelagic governance In conclusion, this research found several governance relevant insights for harvesting in the mesopelagic zone. The set of policies and the insights they provided serve as a promising starting point for stakeholders to learn about harvesting in the mesopelagic zone. Considering the mesopelagic decision arena, this study shows that current marine governance is unprepared to manage the magnitude and variety of the impacts harvesting can have on the mesopelagic biomass and its carbon sequestration function. Also, this research strengthens the call for including the mesopelagic zone and its role in the climate in future governance. These findings facilitate a discussion between stakeholders, which was previously impossible due to the deep uncertain character of the mesopelagic zone. This study is a first demonstration of the added value of MORDM for decision making on an intricate system like the mesopelagic zone.

MORDM
System Dynamics
Modelling
EMA Workbench
Mesopelagic zone
Ecology
carbon sequestration
Uncertainty

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Student theses

master thesis

© 2021 Julie van Deelen