Shark Read online

  First published in 2009

  Copyright © David Owen 2009

  All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without prior permission in writing from the publisher. The Australian Copyright Act 1968 (the Act) allows a maximum of one chapter or 10 per cent of this book, whichever is the greater, to be photocopied by any educational institution for its educational purposes provided that the educational institution (or body that administers it) has given a remuneration notice to Copyright Agency Limited (CAL) under the Act.

  Allen & Unwin

  83 Alexander Street

  Crows Nest NSW 2065

  Australia

  Phone: (61 2) 8425 0100

  Fax: (61 2) 9906 2218

  Email: [email protected]

  Web: www.allenandunwin.com

  Cataloguing-in-Publication details are available

  from the National Library of Australia

  www.librariesaustralia.nla.gov.au

  ISBN 9781741750324

  eISBN 9781741760743

  Internal design by Lisa White

  Index by Puddingburn Publishing

  Typeset by Post Pre-press Group, Brisbane

  For Leisha, Hilton and Larry

  CONTENTS

  Acknowledgements

  Introduction

  1. Shark Attack: Controversy, Reality, Response

  2. The Way of the Shark Roads: Sharks and Indigenous Societies

  3. ‘This Straunge & Merueylous Fyshe’: Sharks and Europeans

  4. Fathoming the Shark: Evolution, Classification

  5. Shark Biology: Form and Function

  6. ‘Creatures of Extremes’: Descriptions of Sharks, Rays, Skates and Chimaeras

  7. ‘An Incredibly Bountiful Crop’: Shark Exploitation

  8. Shark Conservation: Problems, Solutions

  9. Sharks and Creativity: Visions of Hunter and Hunted

  Glossary

  Notes

  Index

  ACKNOWLEDGEMENTS

  I would like to convey my thanks to the following who generously provided information and advice: John Stevens, CSIRO Marine and Atmospheric Research; Matthew T. McDavitt; Jeffrey Gallant and Chris Harvey-Clark, Greenland Shark and Elasmobranch Education and Research Group. I am also indebted to the work of the late R. Aidan Martin, whose enthusiasm and knowledge was inspirational to me. Needless to say any errors of fact or supposition are mine.

  INTRODUCTION

  There are many classic shark stories. Here is mine. Early in my research into this book I keyed into Google the phrase, ‘Evolution of the batoids’. Quick as a flash Google shot back, ‘Did you mean “evolution of the bastards”?’ It became apparent that the language of sharks is not universally known—the skates and rays, close relatives of sharks, are the batoids—and this cyber communication also ironically seemed to confirm our irrational dislike of sharks. In this book’s first chapter there is a description of a tragic event, a gruesome death of a surfer, one response to which refers to the sharks involved as ‘bastards’. Such reactions are understandable. But they also reaffirm our highly ambivalent attitude towards the natural world. This book is not just about sharks but about our complex association with them over thousands of years, and the grim fact that after half a century of intensive marine exploitation and habitat destruction we are rapidly sending many species, both well-known and little-known, into extinction.

  The unusual terminology of these animals extends to neoselachian, elasmobranch, chimaera, holocephali, chondrichthyan. Yet these ancient and arcane Greek-root terms are the sum of our modern fears: the fishes that are grouped together because their skeletons are made of cartilage rather than bone. Not only is the formal terminology of the world of sharks confusing to laypersons; even fundamental definitions seem arbitrary. Thus the monumental The Compact Edition of the Oxford English Dictionary defines ‘selachian’ as ‘the sharks and their allies’, a very broad sweep of the canvas. The chondrichthyans represent no more than five per cent of fish species. Their evolutionary histories are closely intertwined, the skates and rays having evolved as bottom-dwelling ‘flat sharks’, although recent molecular studies suggest that the long-held, science-based evidence for this may be in need of revision. Furthermore, there is much debate and disagreement over the taxonomic structures within the shark, skate and ray orders and families. Again, this is understandable: the meagre shark fossil record is hard to decipher and even with today’s sophisticated technologies it is difficult to study the biology and habits of many marine creatures, as their habitat ranges are vast and they live at great depths.

  So it is that at both the scientific and popular levels sharks continue to confound our perceptions of them. Proportionately very, very few people study sharks, dive with sharks, or handle sharks in the course of professional work—and far fewer still are those injured or killed by sharks. For almost everyone, therefore, shark knowledge derives from aquariums, television documentaries, feature films and YouTube clips, media stories and reportage and of course books, the covers of which all too often feature the gaping mouth of a great white shark—surely the most overused and misleading animal image of all time. But it is that very overuse that is so informative about us.

  In 2008 the US Library of Congress catalogue listed well over 500 books with the word ‘shark/s’ in their titles (and twice that number of titles with the word in their subject headings). Here is a short selection of these titles; it is a revealing snapshot:

  • Sharks: The silent savages

  • Breakfast with Sharks: A screenwriter’s guide to getting the meeting, nailing the pitch, signing the deal and navigating the murky waters of Hollywood

  • Sharks: History and biology of the lords of the sea

  • Sharks and Sardines: Blacks in business in Trinidad and Tobago

  • The Jaws of Death: Shark as predator, man as prey

  • Loan Sharks and Their Victims

  • Shark Liver Oil: Nature’s amazing healer

  • The Nightmare World of the Shark

  • Sharks and Shipwrecks

  • Chomp! A book about sharks

  • Peace Skills: Swim with the dolphins, not with the sharks

  • Close to Shore: A true story of terror in an age of innocence

  • Bloody Waters: Terrorizing shark tales

  • The Man Who Rode Sharks

  The mid-1970s Jaws phenomenon, both novel and film, demonised the great white shark (Carcharodon carcharias) by cheaply enthralling and horrifying millions of people. It also created such a counter-wave of interest in the elasmobranchs that what is now a major worldwide conservation effort aimed at protecting sharks can in large part be dated back to that negative cultural exploitation of a top-order marine predator. It’s most ironic. And fitting, too, that the late Peter Benchley, author of the novel Jaws, became a leading figure in the elasmobranch conservation movement. But the complex nature of human–shark interaction is not a modern phenomenon. This book analyses over two thousand years of it. And Jaws the story, by tapping so successfully into the fear-driven aspect of that complexity with unexpected results, is used as a framing device for this book.

  Tragically, a far more ancient cultural exploitation of sharks has become one of the greatest threats to the survival of some species in the twenty-first century. During the Chinese Qing Dynasty, from the seventeenth to the early twentieth century, shark’s fin soup became established as a luxury reserved for emperors. It has ever since retained that highest possible social status, not just because it is protein-rich and has a texture of strand-like silkiness in the mouth, but because it is expensive. The great economic boom in China that beg
an towards the end of the twentieth century put this expensive must-have delicacy within reach of millions of people, generating unchecked slaughter of sharks at sea, with the living animals, their fins hacked off, often thrown back into the water to sink and die.

  Reducing and controlling shark finning is a major concern of the many environmental entities that have come into being since the 1970s. They are also concerned with an equally wasteful and destructive form of elasmobranch exploitation, one that enters almost every western kitchen and restaurant. Commercial fishing, whether by trawl, net or longline, brings up something in the order of 100 million tonnes of elasmobranchs every year, much of which is discarded as unwanted bycatch. Waste and cruelty apart, these exploitation practices are unsustainable because of the slow reproductive biology of sharks.

  In 2008 a team of research scientists operating at the fossil-rich Gogo Formation in Western Australia made a unique and instantly famous discovery, a 380-million-year-old female placoderm, an ancient shark fossil, with an embryo attached to it by its umbilical cord. (It has been named Materpiscis attenboroughi in honour of David Attenborough.) Not only does this confirm that the shark lineage is ancient; it also demonstrates the method of reproduction is very different to that of the bony fishes, the teleosts, which reproduce by the male fertilising eggs ejected by the female into the water. It is not known why elasmobranchs, like mammals, mate and and internally fertilise, but one consequence of this method of reproduction is that litters are generally small. Furthermore—again, unlike teleosts—sharks can take many years to become sexually active. Perhaps these life history parameters have always ensured that the elasmobranchs, being the predators and scavengers of the oceans, don’t overpopulate. But it makes them particularly threatened by exploitation.

  The one thing that everyone knows about sharks is that they have lots of teeth. In some species, there are many hundreds of sharp, multi-shaped teeth in the mouth at any one time. Others have pavement-like crushing dental architecture. As will be described in detail, the sophistication of shark teeth and jaws is astounding. And other shark attributes, such as their numerous sensory systems, and the body streamlining of the fast open-ocean species, have been studied and adapted to various human technological ends. Not so long ago that would have seemed laughable, when sharks were generally ignored or, worse, despised.

  Shark intelligence is impossible to understand. Yet the most feared shark seems almost to know us:

  Carcharodon carcharias is renowned for his tendency to raise his head above the surface of the sea to observe the topside activity of men in boats. This unnerving habit, unique among all shark species, has been well documented by seafarers the world over including those who work on, and cruise, Tasmanian waters. A number of island fishermen have experienced the heart-stopping moment when a white pointer’s head has suddenly emerged above the waterline alongside their vessels. All agree that the sharks in question were watching them, even assessing them.2

  The smallest known elasmobranch is the dwarf lantern shark (Etmopterus perryi), growing to a maximum of just nineteen centimetres. The largest elasmobranch is the whale shark (Rhincodon typus), which may grow to more than fourteen metres in length. This photograph of a stuffed whale shark was taken in Miami, Florida, c. 1912.1

  The elasmobranch species count is currently in excess of 1200, most of which are small, unobtrusive and harmless. New species are regularly discovered as research into these animals intensifies. The diversity of sharks is bewildering, yet their collective age has meant that every single species, no matter how little understood by us, has evolved over millions of years to take up its specific niche in the vastness of the oceans—and, in a few cases, in freshwater systems. This book describes a representative selection of species, from the famous to the innocuous, the common to the rare.

  Not only is there is no such thing as a boring shark, our own long-term survival, through the health of the seas, relies on them, and the battle to save the planet’s sharks has become a deadly race against time.

  1

  SHARK ATTACK

  Controversy, Reality, Response

  The black fin seems graffitied on the [cinema] screen. Like the one drawn on the Amity girl [advertising billboard] it has no depth of field—it looks extraordinary because it’s so literal-minded, the opposite of abstract. And we can’t help but snigger as this big, black figurative fin sneaks up behind a pretty girl and is noticed by bathers who start yelling and heading for the shore. But first, they stare straight at it. Straight into the camera. For a few seconds, we are the shark, and you know what? These feeble bathers are fair game.1

  As this analysis of a scene from the 1975 movie Jaws suggests, the relationship between shark and human is a complex one. Make-believe and reality are intertwined as comedy competes with horror, popular entertainment feeds off gruesome tragedy. Like a skull and crossbones, a triangular fin in water is a profoundly evocative symbol. Yet very few of those fins ever ‘attack’ people.

  A totally incorrect perception of sharks, but one that stubbornly persists, is that they are inherently a danger to human beings. Equally wrong is the belief that large predatory sharks exist in a state of constant hunger and are therefore reflexively conditioned to attack other living things. This is the shark as mindless eating machine, epitomised by an infamous four: the great white shark, the bull shark (Carcharhinus leucas) and the tiger shark (Galeocerdo cuvier) inshore, and the oceanic whitetip shark (Carcharhinus longimanus) the open ocean hunter.

  Jacket cover from the 1974 novel Jaws by Peter Benchley. (Used by permission of Doubleday, a division of Random House, Inc.)

  The very term ‘shark attack’ is misleading because it implies that a feeding shark is savage and indiscriminate. A child mauled by a family pit bull terrier, however, is by definition attacked. According to zoologist David Pemberton:

  There are many reasons to attack. Fighting dogs are trained to fight other dogs and food has nothing to do with it. Animals fight over food, space, dens (which is a form of space) and breeding. Some will fight to defend other animals, one example being a hippo saving an antelope from a crocodile. A leopard seal can kill a person by drowning them then letting them go; this appears to be space competition. A leopard seal on the other hand can kill or try to kill a person by punching through the ice and grabbing them: this suggests it is after food and sees the human in the light of other prey it takes in this manner, such as emperor penguins. A predator attacks for food and this is clearly proven if the prey is eaten. Sharks killing humans usually eat large amounts of the prey. Pit bull dogs attacking people seldom eat them. The trained killer attack dog loses its urge to keep attacking once the prey is still—hence for many species playing possum is a strategy to stop an attack. The shark does what it is developed to do and that is to survive through eating.2

  Many shark researchers refer not to attacks but to incidents or interactions, being rare chance encounters with a variety of outcomes, from death to minor lacerations.

  It is interesting that prevailing scientific opinion at the turn of the twentieth century was that sharks were of a cowardly nature and had weak jaws. An eminent American scientist, Dr Frederic Augustus Lucas, whose opinion was sought at the time of a horrifying spate of incidents along the New Jersey coast in 1916, concluded that ‘no shark could skin a human leg like a carrot, for the jaws are not powerful enough’3—let alone bite through a femur.

  A common but controversial belief is that sharks often mistake their human victims for other forms of prey. While this usefully overturns the notion that sharks target human beings, the reality is that millions of years of evolution have equipped sharks with an array of highly attuned prey-identifying sensory capabilities, including electrical detectors, acute senses of smell and hearing and exceptional eyesight in some species. When a shark is uncertain about a potential food source, it is likely to purposefully approach and investigate, nudging or biting. Furthermore, the feeding regimes of the named four species are not excl
usively predatory, because they all scavenge. Thus an object bobbing on the surface, be it a surfer, a seabird, a chunk of whale blubber, a person or dog swimming, or a corpse in a river or far out sea, is indeed fair game.

  Common explanations for why sharks mistake human beings for marine prey that is part of their normal diet are that the flash of jewellery or other bright objects, and the pale soles of feet, resemble shoaling fish. Likewise, the erratic splashing of a bather or swimming style of a dog is believed to mimic marine creatures in distress, although it is just as likely that surface turbulence attracts sharks regardless of how it is made (sharks are known to bite boat propellors).

  The most compelling case of mistaken identity, widely believed to be true, relates to great white sharks and their primary prey, pinnipeds (walruses and seals). The belief is that a person in a black wetsuit on a board, when seen from under water backlit against sky, sufficiently resembles a pinniped to become a target. Respected ichthyologist R. Aidan Martin rejected the notion of mistaken identity, believing it to be ‘completely false’, based on his observations of great white shark hunting behaviour at South Africa’s Seal Island. The great white is an ambush predator which typically stalks from below then launches itself up at its chosen target. Martin observed many attacks on seals, in which ‘the sharks would rocket to the surface and pulverize their prey with incredible force’. By contrast, humans are frequently investigated with ‘leisurely or undramatic behavior’ in order to determine their edibility, and this may include an exploratory bite.4 The fact that a great white shark has excellent eyesight should also be considered.

  The case against mistaken identity is strengthened when considering that a shark, or any predator for that matter, will not expend unnecessary energy against a motionless or slow-moving source of potential prey. In 1987 Craig Rogers, a 40-year-old landscape contractor, was surfing with a friend off Santa Cruz, California. As he sat on his board, his legs dangling, a movement made him look down and he saw a huge shark biting his board, next to his hand. It had come up so stealthily that Rogers hadn’t heard it, and then, ‘he watched the shark gently release his board and sink like a submarine.’ Furthermore,