Capturing Spatial Behaviors of Observed and Unobserved Fishing Over Time Using Vessel Monitoring System Data
School of Fisheries and Ocean Sciences, University of Alaska Fairbanks
- Jordan T. Watson, PhD program
Many studies have focused on the response of commercially relevant fish populations in the North Pacific to physical and biological dynamics within their ecosystems (e.g., climate variability, oil spills). We propose instead to focus on the resilience of commercial fishers themselves and to better understand the adaptive capacity of fishing fleets to such dynamics. For example, how far north are fishers willing to follow shifting fish populations? Are fishing trips longer during warmer years and do they subsequently spend less time in local port communities? Such simple questions are predicated on knowing when trips start and stop, where vessels fish, and how many miles they travel. For trips with fishery observers these questions are easy to answer, but observer coverage varies across fleets and years. Vessel monitoring systems (VMS), however, transmit a vessel's location at regular intervals (about 30 minutes) and they have been mandatory on all North Pacific vessels targeting pollock, cod, and Atka mackerel since 2002 (and additional fisheries and sectors in subsequent years). We will use VMS data to reconstruct trips and thus to determine durations and distances traveled for thousands of trips over more than a decade, regardless of observer coverage. Models based on VMS data also enable us to predict when vessels are fishing, and thus we can better characterize how fishing effort is distributed spatially and how resilient those spatial distributions may be over time. Moreover, these models also allow us to compare fishing locations for observed and unobserved vessels. In the context of resilience, this approach will ensure that the characterization of vessel movements and fishing locations is representative of entire fleets and not only the observed portions. This approach can be extended to all Bering Sea and Gulf of Alaska fleets with VMS.
For more project information, please see the 2016 news story ”Pollock fishermen may struggle to maintain catch numbers as oceans change.”
With a changing environment, shifts in the timing of physical and biological processes, locations of marine populations, and the structure of marine ecosystems are inevitable. Many of these changes may require fishers to redistribute their effort in time and space and even to target different species. By examining changing fishing patterns and deliveries, it becomes possible to model how changing fishing locations are impacting the ports and processors where fish are delivered, and how longer trips may affect fishers’ stress and profitability.
Why is this an Alaska Sea Grant project?
As emphasized in the Sea Grant Strategic Plan, Alaska communities, ecosystems, and fisheries are experiencing the impacts of climate change firsthand. Many Alaska community economies are reliant on fish deliveries to processing plants and on the economic contribution from fishing crews while in port. Meanwhile, the current management of fishery ecosystems has developed around historic spatial distributions of fishing effort. As effort responds to ecosystem shifts, different habitats and species (target and nontarget) may become exploited and patterns of vessel deliveries and contributions to port communities (and economies) may change. Our work will characterize how fleets and their spatial distributions are changing over time, providing an opportunity for management strategies to support community and economic resilience.
NOAA Fisheries, Alaska Fisheries Science Center
NOAA Alaska Regional Office
What researchers learned
Fishermen seek to maximize profits so when choosing where to fish, they must consider interactions among the environment, costs, and fish prices. We examined catcher vessels in the US Bering Sea fishery for walleye pollock (2003–2015) to characterize fisher responses to environmental change (e.g., abundance and water temperature). When pollock were abundant and water warm, the fleet fished in similar locations. When temperatures were cooler or pollock abundance declined, two fishing strategies emerged, depending on the processor where a vessel delivered. One vessel group, whose catches were more likely to become fillets, often made shorter trips, requiring less fuel and time at-sea. A second vessel group, whose catches were more likely to become surimi, traveled farther from port, to regions with higher catch rates but generally smaller fish. By fishing in different locations to satisfy different markets, the fleet sustained revenues and buffered against environmental change. We identify a suite of socioeconomic indicators of the impacts of ecosystem change and illustrate that a one-size-fits-all approach may be insufficient for assessing the resilience of fleets.
Alaska Sea Grant researchers use variations in fishing vessel trip data as a proxy for a changing marine environment
Relevance: A changing marine environment is resulting in shifts in timing of physical and biological processes, locations of fish populations, and ecosystem structure. The changes may require fishermen to redistribute effort in time and space to target species differently. By examining changing fishing patterns and deliveries, it becomes possible to model how changes impact ports and processors where fish are delivered, and how longer trips may affect harvester profitability. Answers to questions such as, how far north are fishermen willing to follow shifting fish populations, are fishing trips longer during warmer years, and do fishermen subsequently spend less time in local port communities, can help fishery managers, communities, and industry prepare.
Response: Alaska Sea Grant–funded researchers used vessel monitoring system (VMS) data and fisheries observer data to reconstruct fishing trips in the Bering Sea and Gulf of Alaska. VMS transmits vessel locations and have been mandatory on Bering Sea pollock vessels since 2002. Researchers determined durations and distances traveled during more than 24,500 trips made by pollock catcher vessels between 2008 and 2013.
Results: Researchers tested their experimental approach by comparing observer data (available for about half of trips) with estimated trip durations. Their highly accurate method (less than 5% error) gives strong support for reconstructing the behaviors of unobserved trips. They found that larger pollock vessels may be more resilient to shifting pollock distributions because they can travel farther to follow the fish. However, during low abundance years large vessels were not immune to the lower catches per day experienced by smaller vessels.
Recap: Alaska Sea Grant researchers found vessel monitoring data and fisheries observer data closely conformed for assessing pollock vessel trips in the Bering Sea and Gulf of Alaska, and large vessels may have more resilience to fish location shifts caused by environmental change; the research could provide a tool for agencies to evaluate the impacts of different regulatory actions on fishermen and communities.
Watson, J.T. 2017. Quantifying fisher responses to environmental and regulatory dynamics in marine systems. Ph.D. dissertation, University of Alaska Fairbanks, SGT-17-03, 124 pp. http://hdl.handle.net/11122/8146
Watson, J.T. and A.C. Haynie. 2016. Using Vessel Monitoring System Data to Identify and Characterize Trips Made by Fishing Vessels in the United States North Pacific. PLoS ONE 11(10):e0165173 https://doi.org/10.1371/journal.pone.0165173