Sharks may be a growing headache for Gulf Coast anglers, but a new study from Mississippi State University suggests they pose very little threat to reef fish being returned to deep water on descender devices.
Researchers reviewing underwater video of 987 fish descents in the Gulf of Mexico documented just three instances of sharks eating fish attached to descender devices, a depredation rate of only 0.3 percent. All three victims were red snapper, and all three incidents occurred off Venice, Louisiana.
The findings, published September 29 in the North American Journal of Fisheries Management, offer encouraging news for anglers concerned that releasing fish on descending devices might simply deliver them to waiting sharks.
The two-year study, conducted from March 2022 through March 2024, involved 119 fishing trips aboard charter-for-hire vessels operating off Texas, Louisiana, Alabama and Florida. Researchers attached underwater cameras to SeaQualizer descending devices to document what happened as released fish were lowered toward the bottom.
The study included 20 species of reef fish, primarily red snapper and red grouper. Researchers reviewed the video footage for the presence of predators, identified species when possible, and recorded whether fish were attacked during their descent.
Although sharks, dolphins and goliath grouper were observed in the underwater footage, only sharks were documented actually taking fish from the descending devices. Two of the three confirmed attacks involved blacktip sharks.
The findings are particularly relevant because shark depredation—the taking of hooked fish before anglers can land them—has become an increasingly contentious issue throughout the Gulf. Charter captains and recreational anglers frequently report losing red snapper, grouper and other valuable catches to sharks, sometimes repeatedly at the same fishing location.
But the new research indicates that fish being returned to depth on descending devices face considerably less danger than fish being fought toward the surface.
Descender devices have become increasingly important in reef fish conservation because of barotrauma, the injuries fish suffer when rapidly brought to the surface from deep water. Expanding gases can damage internal organs, cause the stomach to protrude from the mouth and leave fish unable to swim back down after release.
Descending devices allow anglers to return fish to depths where increased water pressure can help reverse the effects of expanding gases, improving their chances of survival.
The Mississippi State research suggests anglers can use these devices without substantial concern that sharks will intercept fish during the descent.
The researchers caution, however, that their findings apply specifically to fish attached to descending devices. The study does not suggest that shark depredation of hooked fish is uncommon or that sharks are becoming less troublesome to Gulf anglers.
The results also do not establish the long-term survival of every fish after it leaves the descending device. Rather, they demonstrate that attacks during the recorded descent were exceptionally uncommon. Researchers also noted that sharks could potentially learn to target descending fish as use of the devices increases, although the study did not establish that this is occurring.
For recreational anglers, the practical message is straightforward: Despite the increasingly frequent complaints about sharks stealing hooked fish, returning unwanted reef fish to depth on descending devices remains a sound conservation practice.
The research was led by Amanda E. Jargowsky of Mississippi State University's Coastal Research and Extension Center and the Mississippi-Alabama Sea Grant Consortium, working with scientists from several Gulf Coast research institutions.
The complete study, Examining Depredation of Reef Fish on Descender Devices Across the Gulf of Mexico, is available through the North American Journal of Fisheries Management, DOI: 10.1093/najfmt/vqag079.