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Economics & Social Sciences Research Program

Using Vessel Monitoring System (VMS) Data to Estimate Fishing Trip Activity and Duration

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Spring 2015
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The Bering Sea American Fisheries Act (AFA) pollock catcher vessel fleet had about half of its trips observed prior to 2011 when the fleet became 100 percent observed. However, despite full coverage during pollock fishing, vessel monitoring system (VMS) data suggest a large number of fishing and non-fishing trips were taken by these vessels outside of the pollock fishery and thus remain uncharacterized. By resolving characteristics of entire fishing trips, a broader picture of fishing patterns and deliveries can be exposed, and can facilitate an examination of fishers’ behaviors. Using VMS data that tracks vessel movements, we reconstructed approximately 24,500 fishing and non-fishing trips made by these vessels from 2008 to 2013. Our algorithmic approach uses a series of spatial and temporal filters, as well as fish ticket data, and it nearly doubles the number of trips described from observer data alone. Compared to observer data, our approach estimated the total days at sea with ~2.1 % error; 83.4 % of individual trip durations were either estimated with < 5 % error or were within the expected error for a given trip and VMS polling frequency.

We further characterized each trip as an AFA pollock fishing trip, a non-fishing trip, or a non-AFA fishing trip. Our approach provides a foundation for resolving several critical components (days at sea and distance traveled) of the variable costs to fishers, as well as a method by which to observe how vessels switch their fishing behaviors over time. It also establishes a framework around which longer term changes in fleet behaviors can be monitored in the context of shifting environmental conditions, migrating species distributions, or the implementation of new management regulations. 

The extensive observer coverage of the Bering Sea pollock fleet allows us to compare VMS-based estimates with observer trip-time estimates, which facilitates tests of our assumptions and will enable similar estimates to be made of all of the fleets and vessels which carry VMS in Alaska and in other locations. 

By Jordan Watson and Alan Haynie



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