The Shark Hunter

The Shark Hunter

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The Shark Hunter

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by Douglas Page, © 1998 Ken Goldman knew as a boy how he would spend his life. On an ocean fishing trip as a youngster once, Goldman was beguiled by sharks the instant he saw a Mako climb from the water like a slicing, grey missile and filch a catch from a fish line. "I just thought it was an outrageously beautiful fish. Even as a twelve year old kid I felt a thing that beautiful couldn't be evil. Fish aren't evil." Soon thereafter the book, and then the movie, "Jaws" exploited public fear of the Great White Shark, in the process motivating Goldman to seek a more meaningful balance. He become a professional marine biologist.

Bio

Now Ken Goldman stalks sharks. Not to claim trophies or to rid the world of a what some consider a menace. Goldman tracks sharks in search of knowledge, filling a void pivotal to the very survival of sharks as a species. There is a critical lack of information about shark numbers, behavior, biology, distribution and life history. The less reliable information, the more public indifference and hysteria there is about sharks. Without a clearer public appreciation, shark numbers will continue to dwindle. They are already in danger of becoming more an echo than a song. Sharks suffer from the same low public image as wolves, bats, spiders and snakes. Militant ignorance has cast all these species as sinister predators, thanks in part to such enduring fables as "The Three Little Pigs", "Little Miss Muffett" and prurient movies like "Dracula", "Jaws" and "Arachniphobia". Goldman, now an elasmobranch ecologist at the Virginia Institute of Marine Science at Gloucester Point (the school of marine sciene for the college of William and Mary), is one of a special breed of scientist devoting their talents to the study of sharks and to shark conservation, who bob around on the ocean rim, waiting with their sensors, their tags and their awe, hoping to enlighten us about the details of creatures so much of which remains unknown or misunderstood. Sharks are not, for instance, the ravenous man-eaters portrayed by popular myth. "Worldwide, there are probably 70-100 shark attacks [on humans] annually, with between five and 15 deaths," said George Burgess, director of the International Shark Attack File at the Florida Museum of Natural History, which maintains an historical record of nearly 3,000 shark attacks. According to the Los Angeles County Museum of Natural History, more people in the U.S. are killed by pigs each year than by sharks. As a result of so much prolonged, negative publicity, some shark species are hunted and slaughtered with such an indiscriminate vengeance their very existence as a species is now threatened. Millions more die in the webs of the longline swordfish and tuna fisheries - drift nets 50 km in length that dangle in the sea like drapes of death, trapping every creature in their paths, including whales, turtles and sharks. Finning - the practice of fin amputation for the benefit of those with a taste for shark-fin soup leaves unknown numbers of discarded, mutilated sharks to drift to bottom to die. Sharks, lacking swim bladders found in other fish, have no natural buoyancy. If they stop swimming they sink. Just one 'fin' boat can maim 200 sharks a day. Even in shark fisheries low reproductive rates in most sharks makes them vulnerable to over fishing. There is a history of collapse in past shark fisheries. In California the soupfin shark (C. zyopterus) supported the commercial fishery in the 1940s. "That shark population crashed after World War II," said Burgess. "Even today, 50 years later, the population has not recovered its former abundance. When shark biologists talk about the frailty of sharks from a fishery standpoint, it's built on the fact that http://home.earthlink.net/~douglaspage/id90.html (1 of 4)6/10/2009 11:06:19 AM

The Shark Hunter

recovery is a decades-long process, not a yearly process." Sharks need their image rehabilitated but, since they aren't likely to attract the image magicians from Madison Avenue, they'll have to settle for the Ken Goldmans of the world. From the efforts of Goldman, and scientists like him, the body of reliable shark knowledge grows at a pace similar to the rate of shark maturity and reproduction. Slowly. Shark research is different than the study of other living things. Birds, bears and bacteria can be tracked or observed mostly at the convenience of the researcher. Shark research, however, is more often at the convenience of the shark. If a shark doesn't approach the researcher at or near the surface of the ocean very little research is possible. "We know a lot more than we used to," said Goldman, "but when it comes to a lot of basic biological questions - gestation, reproductive frequency, where they mate, how long they live we don't know very much. There's a lot of science to be done." Goldman is currently involved in three projects addressing the void of elasmobranch information, including a study of white shark (C. carcharias) feeding behavior off California; a fisheries biology assessment of several species of shark in the Atlantic; and an effort to discover aging, growth and population demography of salmon sharks in Alaskan waters. Only the Atlantic study is funded, by the National Oceanic and Atmospheric Administration (NOAA) and the Virginia Marine Resource Council. The other two efforts are self-funded. "It's very hard trying to get money to do something no one has ever done," Goldman said. " THE FARALLON ISLAND WHITE SHARKS "With the white sharks we've been looking at their body temperature because they're a warm blooded, thermal regulating animal, which is unique for sharks," said Goldman. Of the 370 species of shark, eight species, including C. carcharias, have a vascular system that lets them thermoregulate. White sharks, like tuna, possess rete mirabiles, sites of heat exchange that allow the shark to retain heat generated internally rather than lose it through the gills as all other fish do. White sharks have three retia, located in front of the liver, in the muscles above the viscera and in the area above the eyes and brain. Before Goldman's work it was thought the white shark maintained a body temperature eight to 10 degrees above ambient seawater; if the water temperature dropped five or six degrees the shark's body temperature would likewise fall. Goldman has shown that's not the case. "I've been able to demonstrate that their body temperature is a constant 26.5 degrees C regardless of the surrounding water. I believe they evolved this mechanism to allow them to hunt swift, agile prey even in cold water. Without the ability to regulate body temperature they couldn't do that." Goldman obtains body temperature data from readings taken inside shark stomachs. Many white sharks collect at the Farallon Islands, 30 miles west of San Francisco's Golden Gate, to feed on juvenile elephant seals that populate that region of the Pacific. At certain times each autumn Goldman is already there, waiting on the walk of the Southeast Farallon Island lighthouse for the feeding to begin. "We observe about one shark attack a day through October or November," Goldman said. "This is a unique situation that allows us to study the behavior of the animals in natural predatory scenarios. We aren't baiting or chumming or putting any attractants in the water." For the seven years Goldman has stalked the shark in the Farallons, he and his team (consisting of independent researcher Scot Anderson and Point Reyes Bird Observatory field biologist Pete Pyle) use a 17-foot Boston whaler. A prime objective while examining shark feeding behavior is to avoid becoming part of the meal. "The boat lets us get right into where the feeding is going on," said Goldman, "close enough to pat a white shark right on the head. We put a transmitter in the water on a little piece of seal blubber while an attack is occurring. When it gets eaten this gives us internal body temperature based on stomach temperature." It sounds more simple than it actually is. Only three sharks swallowed the transmitter during one recent two-year period. There are abstract rewards, though, even when research objectives are delayed. Having a white shark swimming next to your small boat does not so much inspire fear as awe. "It's fantastic to see such a majestic predator in its own environment," said Goldman. "The more we learn

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The Shark Hunter

about the life history and habits of white sharks the more we can dispel the myths about a 'man-eating creature'. Through science we can come to realize what they actually are - a well evolved, remarkably beautiful and integral part of our marine ecosystem." Up close to the shark Goldman is also able to get tissue samples with a biopsy needle he's developed for a companion genetic study. "We also put other tags externally on the shark, designed to track their movements, look at their swimming depth and figure out their space utilization," he said. Tagging is necessary even to obtain age and growth data because most sharks do not thrive in captivity. Tags are inserted on or below the first dorsal fin. When the same shark is recaptured and measured researchers can determine how long it's been tagged and how much it has grown during that period. One school shark, thought to be 20 years old when tagged, was recaptured 33 years later, indicating a life-span of at least 53 years. Researchers studying the migratory meanderings of land animals are beginning to tag their subjects with transmitters that employ the Global Positioning System (GPS). GPS, however, doesn't work under water so different methods must be devised to track shark ocean excursions. This fall Goldman is scheduled to start attaching pop-off satellite transmitters to some sharks that will eventually yield swimming depth, route and distance data. "We want archival data so we're putting a data-logger on the fish that has a time mechanism. After 90 or 120 days the tag will release from the fish and come to the surface and upload its data to a satellite." One of Goldman's recent findings refutes the popular notion that white sharks are insatiable, eatingmachines. "Based on what I've seen with certain individual sharks we recognize at the Farallons," said Goldman, "they may feed only every three or four weeks, and it wouldn't surprise me that they go longer than that. They may go longer and they may be opportunistic and feed on a fish now and then we don't see, but when you figure if you're consuming 150 or 200 kg of seal blubber all at once that's going to last you a while." DEMOGRAPHICS OF SANDBAR AND SANDTIGER SHARKS Frequently, when Goldman is not in the Farallons he can be found in waters off Virginia assessing population demographics of sandtiger (C. taurus) and sandbar (C. plumbeus) sharks. "My goal is to use some new population models to be able to forecast population numbers better, to help NOAA and the National Marine Fisheries Service regulate the species." Sandbar sharks, especially, are a huge part of the Atlantic commercial fishery. Goldman's research is important because their population is thought to have declined 80 percent in the past 15 years. With the sandtiger Goldman is attempting to determine age and growth parameters on a fish very little is known about. "Yet here's an animal that fits the pattern of sharks extremely well. It grows very slowly. It takes a long time to reach sexual maturity. When it finally reaches sexual maturity it probably only pups two pups every third year. We don't know what age they live to. So any mortality on this species has a large impact." The age of a shark is determined the same as a tree - by counting rings. "I'm in the process of injecting some animals with oxytetracycline (25 mg per kg of body weight), which adheres to the calcium that gets deposited in the sharks' vertebra. You can age a shark by counting calcium rings in the vertebra. When the vertebra is examined under an ultraviolet light you get a big phosphorescent band. So, if I injected a shark a year ago, then look at the vertebra today, maybe there are either one or two bands of calcium between to outer margin and the phosphorescent ring. That would tell me if that shark is depositing one or two rings in its vertebra per year. That means an enormous amount to understanding the biology of the fish. Does the fish mature at six or 12? Does it live to 25 or 50? Not having those answers makes regulation almost impossible." Regrettably, the only way to examine the treated vertebra is through euthanization. "That's the unfortunate process that leads to the end," said Goldman. "You have to euthanize a number of animals and take the vertebra out so that you can regulate the rest of the species. At this time there is no other way to age sharks except by the rings in their vertebra."

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The Shark Hunter

SALMON SHARKS OF PRINCE WILLIAM SOUND Working from fishing boats in Alaskan waters between Seward and Kodiak Island, Goldman's salmon shark (L. ditropis) research combines the methodologies of his other two projects. "This is a shark that hasn't been heavily impacted by fisheries," said Goldman, "so it's a rare opportunity to do an age and growth study. We're going to be injecting animals in the wild with oxytetracycline and tagging them. From fishing catch we'll be recording size and obtaining vertebra to do age and growth. And I'll be able to model the population and look at the demography. We're also be feeding them transmitters to track them and get body temperature data. No one has ever obtained tracking and temperature data for salmon sharks. I can find only three papers in the literature on this animal and one of them was a note describing a new species." Aside from studying sharks merely for the sake of understanding them, there are practical reasons to learn as much as possible about sharks. Sharks exist at the top of their food chains, and as such are important indicators of the health of entire marine ecosystems. Sharks, in fact, as apex predators, help ensure the health of the oceans, which account for four-fifths of the earth's surface. Among many unique characteristics, sharks possess the ability to mysteriously detect the faintest of electrical fields. They also have unusual blood chemistry, heal rapidly and are nearly immune to infections, cancers and circulatory diseases. The mechanisms that permit this resilience are unknown; if they could be understood they may provide clues to combating human conditions and diseases. So far we know more about Mars than we do about cancer immunity in sharks. ................................................................ SUGGESTED READING Compagno, L.J.V., Sharks of the World. An Annotated and Illustrated Catalogue of Shark Species Known to Date. Part 1 - Hexanchiformes to Lamniformes, FAO Fisheries Synopsis 125, Vol. 4, Pt. 1, pp. 1-249, New York (1984). Compagno, L.J.V., Sharks of the World. An Annotated and Illustrated Catalogue of Shark Species Known to Date. Part 2 - Carcharhiniformes, Food and Agricultural Organization of the United Nations, Synopsis 125, Vol. 4, Pt. 2, pp. 251-655, New York (1984). Branstetter, S. (ed.), Conservation Biology of Elasmobranchs, U.S. National Marine Fisheries Service, NOAA Technical Report NMFS 115, Washington D.C. (1993). -endComments? Questions? Corrections? Assignments? [email protected] Return to Home Page.

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