Conference Agenda

Fishing effort is key to assessing performance and sustainability in fisheries, yet its definition varies. Using landing data, vessel monitoring, and satellite observations, we compare fishing effort measures at the trip level. A two-stage estimation of a generalized fishery model is applied to the Northeast Atlantic cod fishery (multi-gear) and the purse seine fleet (pelagic species). Correlation among effort measures is much higher for cod, but maximum sustainable yield estimates are more consistent for purse seine fishery. Despite accounting for gear-, area-, and season-effects, cod fishery parameters remain sensitive to effort definitions, highlighting the need for caution in multi-gear fisheries.

This paper develops a theoretical framework to analyze the impact of transaction costs on Individual Transferable Quota (ITQ) markets, focusing on their effects on quota trading, fishing effort, and biomass dynamics. While ITQs are widely regarded as an efficient market-based instrument for fisheries management, empirical evidence suggests that transaction costs can introduce significant inefficiencies. Extending the insights of Stavins (1995) on tradable permits to the context of fisheries, this study formally incorporates transaction costs into an ITQ model and examines their implications. The analysis demonstrates that, contrary to the predictions of a frictionless market, transaction costs introduce market frictions that affect the reallocation of quotas. Our theoretical results show that initial quota allocations influence equilibrium fishing effort when transaction costs are present, challenging the standard Coasean neutrality result. Transaction costs reduce quota utilization by creating a wedge between buyers and sellers, leading to a misallocation of fishing rights and inefficient effort distribution. This, in turn, reduces harvest levels and results in higher biomass. Furthermore, this reduction in quota utilization affects biomass dynamics, as lower total harvest levels result in higher equilibrium biomass. While the increase in biomass may appear beneficial from a conservation perspective, it arises as a consequence of economic inefficiencies rather than a deliberate regulatory outcome. This highlights a fundamental ecological-economic tradeoff: reducing transaction costs improves efficiency but may reduce biomass levels, especially in low-growth or overexploited fisheries.

In this paper we investigate to what extent resource dependency, which we here define as having few (or no) options to diversify one’s livelihood, affects how fishers, sharing a common fishing ground, respond to increasing resource scarcity. To this end we run a framed dynamic CPR experiment in Thailand with small-scale fishers, where we observe and compare behavioural responses of fishers that are presented with different scenarios (treatments), reflecting different degrees of resource scarcity (none, moderate and severe). The fishers differ with respect to resource dependency. We find that fishers that are more resource dependent respond differently to resource scarcity compared to less resource dependent fishers, but that this depends on the severity of resource scarcity. In the no resource scarcity treatment, more resource dependent fishers exploit more cautiously compared to less resource dependent fishers. Under moderate resource scarcity more resource dependent fishers exploit more aggressively compared to less resource dependent

fishers. Under severe resource scarcity there is no difference in behaviour between the two types of fishers, both types exploit quite cautiously. Our findings contrast earlier empirical findings that resource dependent fishers continue to exploit, or exploit more under resource scarcity. We find that severe resource scarcity can trigger less exploitation of resource dependent fishers. We argue that the common-pool nature of the situation brings an additional dimension to the situation that

can affect behaviour and overall outcomes significantly, and that may explain the result. We suggest that future work focus on teasing out the importance of these different drivers.

Narratives and models drive our understanding of the world. Especially in times of substantial change, formerly well-working narratives and models may lead to beliefs and predictions that do not match observations anymore.

We develop an ecological-economic model of resource management that takes narratives into account. In particular, we allow for both different narrative types and agents switching to more suitable narratives only when deviations between observation and beliefs become too large. Our modeling approach is based on empirical data. This data demonstrates that in the past agents only changed their action when their believes about a resource stocks deviated 25-50% from reality. Further, most agents follow a narrative of agency, meaning that they believe their action impacts the resource stock. Few people follow a narrative of exogenous resource stocks that they cannot influence, i.e. of no-agency.

With our model, we demonstrate that a steady state resource stock depends on the prevailing narrative. For the example of climate change, we show that both emissions and the carbon concentration are smaller under an agency than a no-agency narrative. On the contrary, for a fishery we find that only the fish stock is larger under an agency than a no agency narrative and harvest levels can be smaller or larger. While realized overall profits are larger under an agency narrative, beliefs on overall profits are larger under a no-agency narrative, possibly explaining the prevalence of this narrative type. As the accepted deviations between observations and beliefs also influence outcomes, policy implications emerging from our analysis relate to keeping this difference small, and on including regular updating into resource management.