New research shows even small ships pose deadly threat to North American right whales

right whale
A female North Atlantic right whale with her calf. Credit: Public Domain

It has long been known that ship strikes involving large vessels pose one of the greatest threats to North Atlantic right whales, whose coastal habitats and tendency to stay close to the water’s surface make them vulnerable to such deadly collisions.

New research by Dal scientists suggests that the endangered animals can also suffer fatal injuries if struck by small boats or by large vessels travelling at slow speeds.

“We’ve shown clearly that small vessels can be a threat to whales. We’ve shown that very light, but fast-moving vessels like trans-oceanic racing sailboats can cause potentially lethal injuries to whales, so it means if you’re in a vessel on the ocean, you may be a threat to these animals,” says Sean Brillant, an adjunct in the Department of Oceanography.

“We also showed that there is indeed no safe speed for large vessels when it comes to whales and we are not going to solve the whale death problem from ship strikes simply by reducing speeds.”

Beyond broken bones

Dr. Brillant worked with Dan Kelley, a physical oceanographer at Dal, and former Dal student James Vlasic to construct biophysical models that predict the stresses whales experience during collisions. To do that they used information about right whale anatomy and simple Newtonian physics, along with damage measures gleaned from a database of 40 ship strike events for which pertinent data were available. One observation that prompted their study was that data showed that many whales killed by vessel strikes did not have broken bones. Instead, the 30 to 50-tonne animals suffered from massive internal hemorrhaging, a finding that suggested that collisions can be fatal even if they don’t break bones but sufficiently damage the circulatory system of the whale.

A core objective of the analysis was to determine the mechanical stresses on whales that were associated with a fatal injury, which would then allow predictions of new events under a variety of conditions. The study, published recently in Marine Mammal Science, focused particularly on North Atlantic right whales, but the model is also applicable to 10 species of large whales and all possible sizes.

Users can input a ship’s speed and mass, as well as the species of whale, its weight and length, and the thickness of its blubber, bone and skin. The model will then determine the probability that the resulting strike would be fatal for the whale.

The model shows that vessels of all sizes can cause stresses greater than the critical (lethal) level, and that large vessels produce stresses much larger than this even when travelling at reduced speeds, like 10 knots.

“The analysis for large vessels reveals that the speed limits commonly under discussion in the research and management communities (i.e. 10 knots) will provide only small reductions in the probability of lethal ship strikes,” the paper states.

“Thus, for large vessels, the only practical way of reducing the risk of lethal collisions is to

Read more

How Suckerfish Surf Across Blue Whales Without Falling Off

In 2014, Jeremy Goldbogen, a marine biologist at Stanford University, stuck video cameras on the backs of blue whales, hoping to learn more about their feeding habits. When he retrieved the footage, he realized he had been photobombed. Dozens of Remora australis were treating his research subjects like dance floors, skimming and twisting across them — even as the whales swam at high speeds.

They were “cruising all over the surface” of the whales, he said. “We were not expecting that at all.”

Remoras — also known as suckerfish or whalesuckers — are strange, even for fish. They hitch rides with cetaceans, sharks and other larger creatures of the deep, attaching to them by means of a “sucking disc” that sits on their head like a flat, sticky hat. They then act as a kind of mobile pit crew, eating dead skin, parasites and leftovers off their hosts’ bodies as they’re dragged along upside down.

Despite their appeal, we know very little about them. Many scientists have “looked past remoras to whatever charismatic megafauna they were attached to,” said Brooke Flammang, an assistant professor of biology at the New Jersey Institute of Technology. For a study published Wednesday in the Journal of Experimental Biology, Dr. Flammang, Dr. Goldbogen and others investigated how remoras maneuver while their whale hosts are on the move, bucking our previous view of them as passive hangers-on.

To solve these mysteries, Dr. Flammang and her collaborators built a 3-D digital model of a blue whale. Reproducing a bus-size creature down to the millimeter was “a big problem, literally,” she said.

In the videos, remoras tended to cluster around the whale’s blowhole and dorsal fin. An analysis of how fluid flows around the whale showed these to be low-drag areas protected from the whoosh of water — “kind of like an eddy behind a rock in a river,” said Dr. Flammang. In other words, a safe place to hang your sucking disc.

Next, they looked into how the remoras were able to surf between these sheltered spots. This came down to a slice of water located just next to the whale, which flows relatively slowly even if the whale is going fast. Think of walking down a city block in a windstorm, Dr. Flammang said — the closer you stick to the buildings, the less you feel the gusts.

According to the model simulations, the boundary layer between the whale’s blowhole and dorsal fin is thick enough that a remora can fit mostly inside of it. “It’s swimming in a much lower-velocity fluid than it would be if it were just a few centimeters higher,” she said.

Another analysis, this time

Read more

International study uncovers secret surfing life of remoras hitchhiking on blue whales

International study uncovers secret surfing life of remoras hitchhiking on blue whales
A remora attached to the skin of a blue whale Credit: Stanford University & Cascadia Research Collective. Image collected under NMFS permit #16111.

Sticking to the bodies of sharks and other larger marine life is a well-known specialty of remora fishes (Echeneidae) and their super-powered suction disks on their heads. But a new study has now fully documented the “suckerfish” in hitchhiking action below the ocean’s surface, uncovering a much more refined skillset that the fish uses for navigating intense hydrodynamics that come with trying to ride aboard a 100-ft. blue whale (Balaenoptera musculus).

In a study published Oct. 28 in the Journal of Experimental Biology, an international team of researchers studying the unique fluid environments of blue whales traveling off the coast of Palos Verdes and San Diego, CA has reported capturing the first-ever continuous recording of remora behavior on a host organism, using advanced biosensing tags with video recording capabilities.

The study shows the secrets behind the remora fish’s success in hitchhiking aboard baleen whales more than 30 times their size to safely traverse the ocean—they select the most flow-optimal regions on the whale’s body to stick to, such as behind the whale’s blowhole, where drag resistance for the fish is reduced by as much as 84%. The team’s findings also show that remoras can freely move around to feed and socialize on their ride even as their whale host hits burst speeds of more than 5 meters per second, by utilizing previously unknown surfing and skimming behaviors along special low-drag traveling lanes that exist just off the surface of the whale’s body.

Researchers say the study represents the highest-resolution whole-body fluid dynamic analysis of whales to date, the insights from which could potentially be used as a basis to better understand the behavior, energy use and overall ecological health of the species, as well as improve tagging and tracking of whales and other migratory animals in future studies.

“Whales are like their own floating island, basically like their own little ecosystems. …To get a look into the flow environment of blue whales within a millimeter resolution through this study is extremely exciting,” said Brooke Flammang, assistant professor of biology at New Jersey Institute of Technology and the study’s corresponding author. “Through lucky coincidence, our recordings captured how remoras interact in this environment and are able to use the distinct flow dynamics of these whales to their advantage. It is incredible because we’ve really known next to nothing about how remoras behave on their hosts in the wild over any prolonged period of time.”

Until now, scientists studying the symbiotic relationships between remoras and their hosts in their natural ocean habitat have predominantly relied on still images and anecdotal evidence, leaving much of how they go about their renown sticking behavior beneath the surface a mystery.

International study uncovers secret surfing life of remoras hitchhiking on blue whales
Remora feeding and skimming along whale body. Credit: Stanford University & Cascadia Research Collective. Image collected under NMFS permit #16111.

In their recent investigation, the researchers employed multi-sensor biologging tags with

Read more