New Scientific Study Tracks the Trends in 100 Years of Shark Depredation in Recreational Fisheries

A scientific article recently published in the ICES Journal of Marine Science provides a new look at shark depredation by exploring the past. This study reveals the breadth of shark depredation in recreational fisheries in the waters from Maine to Texas and the U.S. Caribbean over the last 100 years.

Shark depredation occurs when a shark bites or steals a fish hooked by an angler before it can be brought to the boat. While shark depredation has impacted fishermen for generations, both commercial and recreational anglers are increasingly concerned with economic losses from shark depredation as shark populations rebuild.

In order to mitigate this conflict, the team of scientists from academia and NOAA Fisheries sought to understand the evolution of the three key depredation components:

• Anglers
• Target fisheries
• Sharks

This study represents the first time regional experts on shark depredation, including several graduate students, combined their collective knowledge and data to better characterize shark depredation coastwide across Atlantic recreational fisheries. The goal was to clarify high-level drivers of historic trends in shark depredation and identify the species and management entities affected.

"At its essence, shark depredation is the result of an overlap between humans and wildlife," says lead author Dr. Marcus Drymon, Associate Extension Professor at Mississippi State University and Marine Fisheries Specialist with Mississippi-Alabama Sea Grant. "In this case, the overlap is between recreational anglers and sharks competing for a shared resource. Navigating recent increases in shark depredation, real or perceived, requires a broader understanding of how this overlap has evolved over time."

Scientists integrated observations of shark depredation from published literature, angler surveys, and social media to track trends. The approach allowed the team to identify as many unique, species-level target and depredator combinations as possible.

The analysis revealed that shark depredation is complicated. The team identified at least 51 target recreational fish stocks affected by 22 species of shark depredators. The most prevalent shark depredators were species that span distinct habitats (e.g. coastal vs. pelagic) and regions (e.g. northeastern vs. southeastern United States). These sharks also have different management measures in place, which makes mitigating depredation challenging.

The two species most often involved in depredation are bull sharks and sandbar sharks. Under NOAA Fisheries regulations , bull sharks may be harvested while sandbar sharks currently may not be retained by anglers. Both species have been prioritized for new stock assessments.

Shark depredation affects every federal, regional, and state fishery management agency and organization from Maine to Texas and the U.S. Caribbean. Apart from spiny dogfish, all the shark species implicated as depredators are managed by NOAA Fisheries in federal waters. In state waters, the depredator sharks are managed jointly by regional fishery management commissions and/or individual states. Depredated fish are effectively dead discards that are not well documented in fishery-dependent data collection efforts. In some cases, this unaccounted for additional mortality could impact fishery management assessments.

There is no ideal shark depredation solution that will work across all the species and fishery scenarios identified in the analysis. The researchers recommend continued testing of shark deterrents and optimizing harvest of sustainable shark fisheries, among other mitigation options. Scientists, fishermen, and fishery managers affected by shark depredation should continue to work together to develop options to mitigate depredation.

"NOAA Fisheries is grateful to its academic partners seeking to better characterize and mitigate the widespread challenges of shark depredation," says Dr. Tobey Curtis of the Atlantic Highly Migratory Species Management Division, and study coauthor. "The issue remains complex, but this collaborative study hopefully provides a framework for future research and management action."