Commercial fisheries targeting tuna and billfish can sometimes catch sharks as bycatch. This incidental capture is negatively impacting pelagic shark populations. Due to finning bans, most sharks are no longer retained and are discarded at sea. Recent studies have shown that some shark species are more likely to die from injuries incurred during the fishing interaction.
Oceanic whitetip sharks are an important component of a healthy pelagic ecosystem and make up a large portion of the shark bycatch in commercial and artisanal tuna fisheries worldwide (Photo: Mark Royer).
Researchers have found the three main factors that lead to death of a shark:
- Physiology of the species, making some more vulnerable to stress.
- Length of the fishery interaction.
- Methods used to release the animal.
Our shark researchers collaborate with Pacific Islands fisheries observers to measure death rates of sharks captured and released in the Hawaiʻi and American Samoa-permitted tuna longline fisheries. They consider the effects that handling and discard practices have on the sharks' condition and their ability to survive when they are caught and released.
A scalloped hammerhead shark is released after being equipped with a satellite tag that will collect water temperature and depth (Photo: Mark Royer).
We are also working with local fishermen to tag pelagic shark species—oceanic whitetip, silky, and bigeye thresher sharks—whose populations are in decline and find ways to reduce deaths from fishing interactions. Our overarching research focus is to use telemetry (shark tags that transmit signals) to identify the underlying behaviors and environmental conditions that make certain species vulnerable to fisheries capture.
Temperature and depth profile of a mature male oceanic whitetip shark tagged offshore of Kona, Hawaiʻi Island.
With telemetry and new satellite tagging technology, sharks can teach us a lot about the ocean. We use a variety of satellite tags to track the movement and behavior of sharks. The tracks show us their daily behaviors, long-term migrations, and areas of residency, as well as ocean environmental conditions. As the sharks swim, some tags gather real-time and archival data on depths and water temperatures. In this way, the sharks collect oceanographic data as they migrate throughout the ocean, moving from the surface to deep waters while they forage for food. Newer tagging technology will allow shark tags to collect even more ocean data, such as oxygen and chlorophyll concentrations—two very important environmental factors that govern life in the ocean.
A diver carefully mounts a receiver on mooring chains of a fish aggregating device off the Kona coast in Hawai‘i that will detect any tagged sharks in the area (Photo: Mark Royer).
We invite the community to participate in activities such as public tagging workshops, scientific charters, interviews, and citizen science. We seek to apply local ecological knowledge and innovative ideas from participants and fishermen to reduce shark depredation and fishery interactions. We hope to reduce the negative impacts that fishing has on pelagic shark populations and vice versa. Ultimately, the idea is to test bycatch mitigation strategies locally before applying them in high seas and commercial fisheries.
Contact information
For shark tagging inquiries, contact Melanie Hutchinson.
For outreach and workshop inquiries, contact Mia Iwane.
To share your shark interactions and sightings, email pacificsharktagger@gmail.com or submit a form on the Sharktagger page.
