Dead Pilot Whales
Photo: Iain Kerr
May 21, 2001
Monday: Killing Off the Competition
This is Roger Payne, talking to you from the Odyssey. Mine is the aft cabin, and each morning when I wake up, the first thing I look for is to see whether Chris Johnson has left a Zip disc on my floor during the night. It is Chris who shoots and edits video, records sounds, and runs our website, plus the myriad electronic devices aboard Odyssey. Because satellite rates are cheaper at night he uploads each day's log and checks for emails in the wee hours. So when I see such a disc on my floor it means I have email, and this morning, there it was... its magnetic self, filled with possibilities. I was out of my bunk in a flash, hoping for news from home. None. Bummer.
But I'm spoiled rotten to be so impatient. 19th Century seamen would have killed to have my mail system. They had to wait months, even years to receive word from home, and their replies only reached their wives or sweethearts after further delays of months or years, not minutes as we experience today.
The letter Chris had downloaded was from a friend in Papua New Guinea. It included an article from the Papua New Guinea Post Courier saying that Sir Hugo Berghuser, a commercial fisherman and former politician "wants whales in the Bismarck Sea killed to save the fishing industry." According to the article, Sir Hugo thinks Pilot whales are robbing fish off fishermen's longlines... something that seems unlikely for a whale species that eats squid. If it is not sharks or even crocodiles that are responsible, it is more likely that false killer whales (Pseudorca) are the culprits. Later in the article Sir Hugo is quoted as saying; "We must kill the whales...there's too many of them", and claiming that "the whales eat up to 80% of the tuna caught by the long-liners," and later he says that the catch has fallen from 15 tons per month to 4.
A longline is a very long fishing line (some are 50 miles long) marked by occasional poles, between which are widely-spaced floats from which baited hooks are suspended. When a fish takes a bait it fights to exhaustion against the drag of the float and the line and is collected several hours later when the fisher winches in the line to collect the catch. I would certainly expect sharks, whales and other large ocean predators to take at least some fish from longlines, but I would be thunderstruck if it turns out that they were the main cause of the kind of major reductions in tuna catch Sir Hugo is claiming. Such drastic reductions are usually only ever achieved by human overfishing. If fishers here are like fishers elsewhere, a far more likely scenario is that it is they who have caused fish populations to decline sharply, and may have affected fish recruitment by overfishing and/or using nets made of smaller mesh that catch smaller fish. The pattern that has emerged from the vast majority of fisheries studies in every major fishery from all over the world is that rather than predators like whales being the problem it is almost always human fishing practices that cause the big depletions of fish stocks. Which makes sense... after all, whales have occupied these waters for millions of years, maintaining themselves at populations which have always allowed plenty of fish to survive and reproduce.
The history of human fishing is not as commendable.
But I am willing to be educated, and like any scientist would like to find out what's going on. So I hereby offer time aboard my institute's research vessel for those who may be interested in studying
this problem. I suggest that the best approach would be to have our ship, the Odyssey working alongside a tuna boat (say, Sir Hugo's) so that together we can find out what's happening. If Sir Hugo is right, and the whales really are causing such mayhem, I am sure others will join him in asking that they be killed. However, there is a clear precedent indicating that far less drastic methods may solve the problem.
I refer here to a study of a group of false killer whales (Pseudorca) that had learned to steal fish from longliners in Alaska. When scientists studied it, they found that the whales hadn't learned to follow the longline to seek out fish, but only to hang out near the stern of the fishing boat stripping fish off the hooks when the longline was being retrieved. The payoff came when the study demonstrated that it was the sound of the winch turning on that acted like a dinner bell to the whales. The problem was relieved not by killing the whales, but by mounting the winch on rubber mounts (a standard accessory). I don't recall whether the people who did this work tried what seems like an obvious strategy: to turn the winch on at odd times so as to attract the whales when no backdown operation was underway and there were no fish in the offing. Such a procedure might eventually have taught the whales to stop associating the sound of the winch with food.
My life is punctuated with having to stop everything I'm doing and engage with suggestions like Sir Hugo's. Thanks to communication satellites that kind of interruption doesn't end just because I'm thousands of miles from home, at sea. So when I read the article containing Sir Hugo's comments I went down to my cabin to write him a letter and found myself getting more and more embroiled in trying to explain the consequences of a suggestion that has a far bigger negative side than its proponents obviously realize (else they would never suggest resorting to something that has so often been shown to create more problems than it solves, and which presents the very real possibility of destroying the very fishery it sets out to protect). When I finally looked up, the sun had set. The day had passed, and I realized I'd spent the whole day typing. The day's final bummer.
While I was stuck below, the others had been getting samples from sperm whales, seven in all, an excellent data set.
So ends this day.
Log by Roger Payne