By tracking marine species like the ocean sunfish (Mola mola), BioTrack — a project of the Marine Biodiversity Observation Network (MBON) — is uncovering key patterns in biodiversity and making marine animal movement data accessible to stakeholders. Photo Credit: Dr. Austin Gallagher – Beneath The Waves.
Background
The Atlantic is home to a wide diversity of marine species, many of which share habitats impacted by human activities. Identifying areas of the ocean that are important to many different species — and how these hotspots intersect with human activities — is crucial for effective conservation, sustainable management, and overall ocean planning.
That’s the mission of BioTrack , a collaborative project led by Dr. Neil Hammerschlag. Supported by the MBON and the Animal Telemetry Network (ATN), BioTrack is combining satellite and acoustic tracking of marine animals with environmental data and modeling to identify, monitor, and predict changes in marine biodiversity hotspots and use this information to provide practical data products for decision-makers. The project is currently regionally focused on the waters of the United States’ North Atlantic.
“The BioTrack project is highly collaborative, with researchers tagging all different types of species, from tiny river herring to massive blue whales, and everything in between,” said Hammerschlag, Executive Director of the Shark Research Foundation . “Our ultimate goal is to use the resulting information from this effort to help guide sustainable use of ocean resources while preserving biodiversity hotspots.”
Why Ocean Sunfish Are Ideal for Tracking Biodiversity
The ocean sunfish is a large fish that can weigh upwards of 1,000 pounds and span 10 feet from fin to fin. Despite their size, these fish are not well understood. They eat a lot of gelatinous creatures like jellyfish, spend a lot of time on or near the ocean surface, but also make deep dives into the twilight zone (200–1,000 meters) to forage.
For BioTrack collaborator Dr. Austin Gallagher (founder of the marine research organization Beneath The Waves ), these qualities make ocean sunfish ideal candidates for BioTrack. “They are true ocean giants — mobile, visible species that use a variety of habitats,” Gallagher explains. “Tracking them helps us understand not only their movements but also the broader biodiversity hotspots where multiple species converge.”
Ocean sunfish are also believed to be the most fecund vertebrates on Earth, producing upwards of 300 million eggs per year. They frequently spend time at the surface, lying flat on their sides, sunning themselves — researchers think this behavior helps warm their eyes and brain, supporting the deep dives they make in search of prey.
How Do You Tag an Ocean Sunfish?
Tagging these giant fish is no small feat. They’re indifferent to being baited, due to their preference for jellyfish, and are covered in incredibly tough, sandpaper-like skin. Working with anglers over several years, the team pioneered a method that relied on patience, sharp eyes, and angling prowess. Spotters would locate the fish from a boat or small plane, looking for flat bodies basking in the sunlight. Then the team secured the fish with a line and lasso, allowing it to be brought to the side of the boat for sampling and tagging.
“Once they’re alongside the boat, they are actually quite calm,” Gallagher said. “They’re huge and powerful, but docile when handled carefully.”
The tags range from pop-off archival tags that record vertical movements, to real-time satellite tags that track long-distance travel, to short-duration biologgers equipped with multiple sensors. Depending on the tag type, they can transmit data for months or up to a full year.
Early Insights from Ocean Sunfish Tracking
Even in the early stages, the data from tagged sunfish are providing valuable insights. Most individuals remain close to the coast but travel long distances — from Maine to North Carolina — in a short period of time. The team has also observed sunfish gathering near offshore canyons, suggesting they may be taking advantage of upwelling zones for foraging.
“These fish are much more dynamic than we expected,” Gallagher says. “Tracking them helps reveal areas of potential biodiversity that were previously hidden, as the sunfish show intentional selection of offshore seamounts and follow oceanic currents closely.”
As the dataset grows, these ocean sunfish movements will become part of a larger, integrated picture that BioTrack is building for resource managers — supporting tools that can forecast species presence, highlight ecologically important corridors, and guide decisions ranging from seasonal management to long-term spatial planning.
The Future of BioTrack and MBON
The ocean sunfish tagging is only the beginning. BioTrack aims to integrate newly acquired and existing historical tracking data from a variety of marine species — including sharks, sea turtles, seabirds, and marine mammals — to build a comprehensive picture of biodiversity hotspots. All data products will eventually become publicly available through an interactive portal where managers, researchers, and the public can explore biodiversity patterns and their overlap with marine protected areas and human-use areas.
This work was supported by the U.S. Marine Biodiversity Observation Network (MBON), co-organized by NOAA, NASA, BOEM, and ONR through the National Oceanographic Partnership Program (NOPP).
