Multi-level Interactions between Fisheries and Trade : Modeling intertwined social-ecological systems

Abstract: Sustainable and equitable fisheries are central for addressing the challenges of the UN Sustainable Development Goal 14: Life Below Water. International trade, once presented by Walrasian economists as a panacea for fisheries development, has not markedly decreased poverty and has been related to the overexploitation of marine species. In this light the consequences of a continued expansion of seafood trade are highly uncertain and problematic. Two competing theoretical hypotheses predict either overexploitation or recovery of marine species when connected to international trade, respectively. The empirical literature finds trade relationships and connections of local fisheries to a large-volume market critical factors for social-ecological outcomes. Here, I combine these insights to show that multi-level links, between fishers & different markets (market manuscript) and marine species & trade relationships (squid manuscript), are critical to explain diverging social-ecological outcomes. In the market manuscript we model the transition from local, to multi-level (both local and global), to global markets in a two species fishery. We find this transition is non-linear, leading to fluctuations in species abundance as a result of abrupt switches between target species. Critical fluctuations of species abundance driven by new market connections are a result of large shifts in prices for one species and high asymmetries in expected income between the two species. The squid manuscript provides empirical and modeling evidence that cyclical changes in the ocean can drive social-ecological systems outcomes through changing interactions at multiple levels. The interactions between squid population and fishers and squid distribution and trading structures determines benefit distributions in the fishery. The lack of consideration of multi-level interactions related to trade in models for fisheries management is likely associated with a lack of processes for integrating the empirical and theoretical insights of two disciplines at the core of fisheries science. Social-ecological system scholars study more often empirical and fishery economics the theoretical aspects of interactions between trade and fisheries. One process suggested in this thesis to bridge insights from both disciplines in fishery models is the careful study of the important interactions in the empirical case. Comparison of these interactions with observed empirical interactions in other systems informs the model conceptualization that is then embedded in a theoretical framework. This leads to the development of models of intermediate complexity  that integrate insights on regular structures and patterns observed in real social-ecological systems. The squid manuscript exemplifies this integration. We integrate observed multi-level links in a standard fishery model between the squid population fishers and traders, and thus better represent the empirical system.  A continuous dialogue between empirics and theorycan help build models of intermediate complexity. To capture the complex elements of these social-ecological systems, in this young field of study, next to a continuous dialogue priority observed empirical dynamics can help question theoretical assumptions. This study seeks to contribute to the development of fisheries management models more suitable to face contemporary challenges of fisheries management by focusing on how multi-level interactions between fisheries and trade shape sustainable and equitable outcomes.