Modeling the Spatial Dynamics of International Tuna Fleets.

Jenny Sun,Michael G Hinton,D G Webster,Andrea Belgrano

doi:10.1371/journal.pone.0159626

Jenny Sun, Michael G Hinton + Show 2 more

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https://doi.org/10.1371/journal.pone.0159626

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Abstract

We developed an iterative sequential random utility model to investigate the social and environmental determinants of the spatiotemporal decision process of tuna purse-seine fishery fishing effort in the eastern Pacific Ocean. Operations of the fishing gear mark checkpoints in a continuous complex decision-making process. Individual fisher behavior is modeled by identifying diversified choices over decision-space for an entire fishing trip, which allows inclusion of prior and current vessel locations and conditions among the explanatory variables. Among these factors are vessel capacity; departure and arrival port; duration of the fishing trip; daily and cumulative distance travelled, which provides a proxy for operation costs; expected revenue; oceanographic conditions; and tons of fish on board. The model uses a two-step decision process to capture the probability of a vessel choosing a specific fishing region for the first set and the probability of switching to (or staying in) a specific region to fish before returning to its landing port. The model provides a means to anticipate the success of marine resource management, and it can be used to evaluate fleet diversity in fisher behavior, the impact of climate variability, and the stability and resilience of complex coupled human and natural systems.

Highlights

Space-based approaches provide key tools for marine resource management
We started the model in 1997 because there were constraints on the availability of satellite imagery and because the fleet composition was relatively stable by this time following the influx of fish-aggregating devices (FADs)-oriented vessels in the early 1990s
Variation in goodness of fit seems to depend on the homogeneity of fishing strategies within a group rather than the number of observations. For both dolphin mortality limit (DML) and non-DML vessels, goodness of fit measures are generally higher for smaller vessels, which tend to have fewer operational options and more homogenous fishing strategies

Summary

Introduction

Space-based approaches provide key tools for marine resource management. Their use requires anticipating fishers’ response to management action, including their decisions about fishing location and effort to exert at a location. Fleets target different species and sizes of tunas using gear tuned to the particulars of individual vessel operations and fishing locations. They can purchase larger vessels, which provide for economies of scale (reducing the price-per-ton to search for fish), and ships designed for more fuel efficient operations Both increase the effectiveness of fishing fleets, allowing them to exploit larger areas or travel to distant areas more often. We move from measures of fit and a close look at the first set models, and examine the switching region choice model results We relate these fishery-specific observations to the larger problems of modeling fleet dynamics and a broader understanding of patchiness in coupled human and natural systems

Literature Review of Individual Location Choice Model

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Results

Discussion