Marine animals—including whales, dolphins, seals, turtles, and seabirds—often become caught and trapped in nets and lines used by commercial fisheries. These entanglements can inhibit marine animals from moving freely, preventing them from hunting, breathing, and eating normally. They can also cause severe injuries and death.
This illustration shows how fishing lines attached to traps and buoys on the ocean floor present a potentially deadly hazard to North Atlantic right whales. Freeing entangled whales involves a certain amount of knowledge and caution, and should be left to the experts.
Marine mammals getting caught in fishing gear and debris is a growing problem. Each year, thousands of whales and dolphins die from the gear, indicating that fisheries by-catch is a significant human-related cause of cetacean mortality.
David Mattila, the research and rescue coordinator for the Hawaiian Islands Humpback Whale sanctuary, has spent the last 25 years cutting large whales free. He stressed the importance of leaving the rescue work to the specialists by highlighting some of the hi-tech equipment available to them.
Scientists reimagined how sedation can save entangled whales in a smarter, safer way.
Problem
When whales swim up and down the coastline to feed and breed, they can encounter fishing gear in the water. When they make contact with lines, they often roll in an effort to get free. Unfortunately, this makes the gear wrap around their bodies, soon becoming a time bomb, cutting, constricting its flippers, and limiting its ability to feed.It can take weeks, months, or years, but eventually many of these entanglements are fatal.
Solution
We have embarked on our most ambitious project yet: to use sedatives to slow a whale so that it can be safely and effectively disentangled.Small unmanned aerial vehicles – or drones – can help us accurately estimate the weight of the animals and determine the correct dosage of sedative.It can also help us map the entanglement, so the right cuts are made to remove the life-threatening gear.
One of the pieces of equipment that we use to help us free these animals is transmitters,” Mattila says. “Attaching transmitters to the gear ensnaring the whale allows the rescue team the ability to track the animal until proper resources and trained personnel have been assembled, and conditions are favorable to safely cut the whale free.”
In Alaska, the sanctuary program and NOAA Fisheries’ local Protected Resources Division tagged a humpback entangled in a gillnet. The transmitter allowed the team to work on the animal on two different occasions, and free it nine days later. This was the first time transmitters were used to aid in whale disentanglement efforts in Alaska.
Extensive effort has also gone into developing and testing unique and specialised cutting tools that can help remove the gear safely and without causing additional harm to the whales.
