June 7 (UPI) -- Dolphins and other marine mammals are being killed and used for bait in commercial fisheries around the world, new research suggests.
The problem of bycatch, non-targeted fish and marine mammals caught by commercial fishing operations, is a well-documented problem, but less attention is paid to the deliberate targeting of marine mammals and protected species for usage as bait.
A new survey of the scientific literature suggests the use of marine mammals for bait -- 40 mammal species being killed in 33 countries -- is prevalent.
According to the survey, published this week in the journal Frontiers in Marine Science, 80 percent of the mammals used for bait are purposefully killed.
The use of dolphins for commercial fishing bait, most frequently in shark fisheries, is most common in Asian and Latin American, scientists found.
"Killing for use as bait is a primary threat affecting Amazon river dolphins, known as botos -- the species and issue I have studied since my Ph.D. dissertation," Vanessa J. Mintzer, researcher at the University of Florida, said in a news release. "With this global review we wanted to see whether, and where, other species were killed for bait, and learn about possible solutions to stop the problem."
Scientists are still unclear on how the practice is affecting local mammal populations. Mintzer and her colleagues hope researchers already studying the hotspots identified in their work will look more closely at the practice and its impacts on local ecosystems.
Researchers also hope their work will inspire improved conservation efforts in areas where mammals are targeted for use as fishing bait.
In addition to better enforcement of laws against killing marine mammals, scientists suggest sustainable fishing programs and policies, combined with educational efforts, are needed to decrease manmade pressure on vulnerable marine mammal populations.
Scientists suggest the use of mammals for bait often occurs in fisheries that are unsustainable.
"In most instances, the ecology and population dynamics of the targeted fishery species is poorly understood and in some cases the species is classified as threatened, suggesting a fishery sustainability issue that cannot be fully addressed with a substitute for the aquatic mammal bait," researchers wrote in their paper.