By Chase Martin
For the first time, scientists have calculated the effects of drag from fishing gear entanglement on North Atlantic right whales.
Led by the Woods Hole Oceanographic Institution, a group of researchers have published a paper online in Marine Mammal Science that quantified the drag created on these animals from fishing gear like ropes, buoys, and lobster and crab traps.
The North Atlantic right whale is one of the most endangered marine mammals; NOAA scientists estimate there are only around 450 individuals left in the wild. They are primarily found off the East Coast of North America, from their summer grounds in Canada and New England, to their winter and calving areas off the Southeastern United States. Unfortunately, their migration routes coincide with some of the busiest fishing and shipping areas in this part of the North Atlantic.
Scientists are aware of the effects of gear entanglement on the whales’ swimming and diving patterns, understanding that it can deplete their energy. What they didn’t know, though, was what it was actually like for the whales to tow the gear, said lead author Julie van der Hoop, a PhD Candidate in the MIT-WHOI Joint Program in Oceanography. “Is it like wearing an empty backpack or is that backpack overloaded with heavy books? Does removing part of the gear improve chances of survival?” she said in a news release. “These are some of the questions that we were looking to answer with this research.”
Testing fishing gear collected from past right whale entanglements, van der Hoop and researchers from the Center for Coastal Studies and NOAA Fisheries used a tensiometer to measure the drag these gear created. They towed 16 sets of gear behind a research vessel at various speeds and depths.
They found that different types of gear have varying effects on drag, with gear types that include buoys and floats having among the highest increases in drag. Overall, they concluded that gear entanglement results in a 1.5 times average increase on a whale’s drag. A separate study showed that in order to swim at the same speed as a non-entangled whale, an entangled animal would need to exert twice as much energy.
These results provide useful information for rescuers who weigh the risks and benefits of disentangling a whale. For example, by removing 75% of an entangled fishing line, rescuers could decrease that whale’s drag by 85%, relieving much of the burden.
Researchers are looking at this study as a step toward understanding just how fishing gear entanglements are affecting the health of North Atlantic right whales.
To learn more:
- Read the WHOI news release: Drag from Fishing Gear Entanglements Quantified
- Read the study abstract: Drag from fishing gear entangling North Atlantic right whales
Chase Martin is a science communicator and graduate of Scripps Institution of Oceanography who lives and works in Washington, D.C.
Copyright © 2015 by Marine Science Today, a publication of Marine Science Today LLC.