# Fishing fleets as ecosystem sentinels

## TL;DR

Fishing vessel data can detect climate impacts on tuna species, offering real-time ecological insights for marine resource management.

## Contribution

Fishermen are shown to be effective sentinels for detecting ecological impacts of marine heatwaves on tuna distribution.

## Key findings

- Fishermen accurately predicted extreme shifts in tuna distribution during marine heatwaves.
- Fishermen signaled low albacore availability a year before a formal disaster declaration.
- VMS data can provide advanced warning for fisheries disasters and transboundary tuna shifts.

## Abstract

Vessel Monitoring Systems (VMS) data offer near real-time information on where fishing vessels are. It is used by authorities around the world to enforce compliance with fishing regulations. Here, we explore an alternative application for these data: to detect climate impacts on ecologically and economically valuable target species. We find that VMS provides an accurate, real-time indicator of the impacts of marine heatwaves on the location and availability of north Pacific albacore and bluefin tuna. These findings are intuitively credible, since fishing profitability depends on accurately locating and accessing target species. Despite this potential, VMS data are not currently used for operational ecological monitoring. As ocean conditions change, timely ecological information is essential for managing and conserving living marine resources.

Marine apex predators are promising sentinels for detecting the ecological impacts of climate variability and change. Fishermen are increasingly recognized as marine apex predators, and there are extensive satellite-based geolocation data on fishing vessel activities. Despite this potential, the utility of fishermen as ecosystem sentinels remains unexamined. Using one million vessel positions from 600 U.S. vessels, we assess the effectiveness of fishermen as sentinels for the ecological impacts of Northeast Pacific marine heatwaves on tuna distribution and availability. Fishermen were skillful predictors of extreme northward shifts for albacore and bluefin tunas, and extreme inshore shifts for albacore. Fishermen signaled low albacore availability over a year in advance of a formal fisheries disaster declaration request. Notably, fishermen also indicated true negatives during marine heatwaves: periods of anomalous warming but stable tuna distribution and availability. This information could aid management of transboundary shifts during marine heatwaves of albacore from U.S. to Canadian waters and bluefin from Mexican to U.S. waters. Advanced warning of fisheries disasters could expedite the delivery of relief funds for struggling communities. The number of Earth-orbiting satellites is exponentially rising, generating a wealth of geospatial information on fishing vessels. This rich and growing resource can signal otherwise unobserved ecological impacts, aiding rapid management responses to climate extremes.