A couple of years ago, The Deep column featured the following article about animals winning in the human/animal battle for a change. Please enjoy it, and then read on for an interesting update.
THE WHALE’S REVENGE
Although we humans are definitely meat eaters, we also have a soft spot for the underdog. Sometimes animals ‘get their own’ in the constant struggle between animals and humans. The cow that escapes from the slaughterhouse truck, the turkey supposedly destined for the Thanksgiving table at the White house, the NASA chimps that have grown too old to serve; they all receive their reprieves. And when wild animals get the upper hand (or the prize), we invariably cheer.
This happened to me when I read the lovely tale of the recent adventures of longline fisherman in Alaska. We’ve talked before about the terrible toll that longline fishing takes on the world’s fish populations. The lines are several miles long and if they aren’t reeled in frequently, the fish that are caught simply rot in place and die for no reason at all. But apparently, in at least some instances, that’s not what’s happening at all.
Longline fisherman in the Gulf of Alaska began to reel in their lines and discover empty hooks or hooks with heads or partially eaten fish. And that’s when they discovered that they had been “a-fishin’ for the whale” without even trying. Sperm whales, the only carnivores among the large whales, are treating their longlines as gigantic shish-kebobs; plucking lingcod, halibut and the incredibly trendy and expensive sablefish from the handy serving lines. Researchers estimate there are 90 male sperm whales feeding from longlines in the eastern Gulf of Alaska, part of the world’s largest sablefish fishery.
Killer whales in the Bering Sea and Prince William Sound also plunder longlines. And Alaska isn’t the only place it happens. Sperm whales and other toothed whales, like pilot whales, cherry-pick fish catches all over the world.
There’s also been a lot of controversy about all the noise generated by human activity on the ocean. We’ve talked about how far noise travels in the deep ocean and how it could interfere with whale communication. Well, there’s communication going on here too. Scientists have recently figured out that the sperm whales find their dinner-on-a-hook by zeroing in on the sound of the boat engines hauling the lines. But they don’t use just any engine noise. Longliners turn their engines on and off as they haul in their lines, and the on-off pattern is Morse code that spells D-I-N-N-E-R to the wily and intelligent whales.
Longline fishermen are afraid the problem will get worse as the endangered marine mammals increase in number and teach each other the techniques of fish rustling. Sperm whales were once a prime target for whalers, but scientists suspect their numbers are increasing in oceans worldwide, although there are no definitive population numbers.
In an effort to outwit the whales, some scientists have suggested that longliners fish earlier or later in the season, haul in the line without changing engine speed, or make decoy noises with the engine to draw whales to a different area. Fishermen said they will try the methods this season, but many say the large-brained whales are just too smart.
Talk about your poetic justice! I say “Hurray for the whales” and “Keep up the good work” and “Keep ringing that dinner gong, guys, you’ve got some hungry and appreciative customers!” Sometimes the underdog does win!
Keep revving those engines, mate!
Dinner is served! (Sperm whale photo courtesy NOAA Fisheries)
For decades scientists have been intrigued by the variety of sounds emitted by sperm whales, partly due to a popular theory that suggests that the sounds might contain information about the animals’ sizes. But it’s been extremely difficult to demonstrate that a sperm whale’s clicking noises can tell us about the physical characteristics of these most massive marine mammals. Now, researchers at Scripps Institution of Oceanography at UC San Diego are unlocking some of the mysteries of sperm whale sound production.
In a paper published in the May issue of the Journal of the Acoustical Society of America, Delphine Mathias and Aaron Thode of Scripps Oceanography describe for the first time, a direct comparison between the clicking sounds a sperm whale makes and the physical features of the animal’s head, including its size and internal organ structure. The study may prove to be the first step in a new approach for investigating how marine mammals make sounds. This, in turn, may allow their numbers to be more accurately counted.
The roots of this unique study began several years ago in Alaska, when sperm whales developed the ability to steal black cod and other fish from longlines. As was reported in the previous article, the frustrated fishermen began to realize that their longline fishing boats were attracting groups of whales—which typically forage alone— to their longlines, somehow alerting the animals like a dinner bell.
To help fishermen and scientists better understand this behavior, Scripps researchers deployed acoustic recorders on longlines to help identify the sounds that attract whales to the fishing vessels. They reported that it was apparently the on-off sounds of the engines that attracted the sperm whales. Encouraged by these results, the researchers added video cameras to the fishing gear. This led to some unexpected results.
The resulting video, recorded using ambient light at 300 feet, gave the fishermen a clear idea of just how the thieving whales were stealing the fish. They pluck the line at one end to jar the fish free at the other end, just like shaking apples from a tree. The video also gave scientists a chance to match the animal’s acoustics with pictures of its physical features. Sperm whales typically dive to depths from 1,000 to 6,000 feet to catch their prey. It’s DARK down there making it virtually impossible to capture the whales on video. The fact that the animals make foraging sounds at the shallow depths around the fishing vessels is the main reason the Alaska footage is so unique.
The clicks emitted by the whales are produced more rapidly as they approach their targets of interest and are among the loudest and most intense sounds produced by any animal. Their clicks can be louder than a firecracker. But until this video was made, scientists hadn’t been able to get a direct measurement of a whale’s size and the foraging sounds it makes.
The Alaska video allowed the researchers to not only match the size of the whale’s head with its acoustic signal, but allowed them to infer the size of its spermaceti organ, which produces a white, waxy substance previously used in candles and ointments, as well as the so-called ‘junk’ inside the whale’s head. The ‘junk’ is a large organ that’s believed to play a role in transmitting sound from the whale’s head.
The study may be a first step in the broader use of acoustics to help researchers get an accurate count of whale populations. Currently it’s difficult to relate the numb
er of whale sounds recorded to the number of animals present. The ability to tease individuals apart acoustically would be a big step toward solving the problem.
The researchers also hope to eventually identify an individual whale from the sounds it makes. Although we can easily tell our friends apart over the telephone, it’s been very difficult to do this with the whales.
The video also may help fishermen to reduce sperm whale encounters with their gear. Besides the fact that the wily whales are stealing the fish which is bad for the longliner’s ‘bottom line’, these encounters are potentially dangerous to both humans aboard the boats and the whales because of entanglement. If you’re familiar with the term “Nantucket Sleigh Ride”, you know what I mean!
The video recording has also encouraged the U.S. National Marine Fisheries Service to start deploying acoustic recorders during black cod surveys off the Alaskan Coast to measure the scale of the sperm whale problem.
Snapshots from the unique sperm whale video shot off Sitka, Alaska. (Credit: Scripps Institution of Oceanography, UC San Diego)