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New insights into the world's most-feared predator.
Sharks are exquisite creatures refined and honed by competitive forces that have lived in balance with ocean prey for millions of years. They live in every ocean habitat on Earth, from shallow tide pools to the deep abyss, and from the open ocean to where rivers meet the sea. In Sharks a top research scientist explores what has made sharks such successful predators, how they differ from other animals in their biological success...
New insights into the world's most-feared predator.
Sharks are exquisite creatures refined and honed by competitive forces that have lived in balance with ocean prey for millions of years. They live in every ocean habitat on Earth, from shallow tide pools to the deep abyss, and from the open ocean to where rivers meet the sea. In Sharks a top research scientist explores what has made sharks such successful predators, how they differ from other animals in their biological success and what unique advantages evolution has conferred. Sharks is illustrated with uniquely sourced photography demonstrating newly observed behavior, scientific findings and recent developments in our understanding of how they live. Sharks is both a spectacular visual celebration, and a scientific document that explores in detail their unique physiology.
A powerful swimming stroke is delivered from sharks' muscles directly to their tough skin shell forcing their body to "inflate" like a car tire with each flex, then quickly become fluid to glide as the muscles relax. By diving through the various water layers, a shark may locate and follow chemical scent trails that could lead to food concentrations. Thus a shark moving from one temperature layer to the next can expose its sensory equipment to new chemical cues and potentially new food sources. Some deep-sea sharks also lure prey with their light-producing organs.
Salvador Jorgensen has combined the latest discoveries of new species, newly-documented shark behavior, and the best photographs, to give a "state-of-knowledge" picture of sharks. Unique pictures of shark births, recently discovered creatures from the Ocean Census research, and details of sharks' skin, eyes, teeth and heads (including a comparison of nine different hammerhead varieties) make this a book every shark enthusiast will want. It will also debunk many myths about shark behavior, and give libraries a true, 21st-century documentation of a very popular wild animal.
Sharks features illustrated profiles of species living in the shallow reefs and also those living in the open ocean along with a unique "cladogram" family tree that opens into a gatefold and profiles every known species.
Table of Contents
1 The Diversity of Sharks
2 Life Histories
3 Form and Function
4 Strategies and Behaviors
5 Threats and Hopes
Excerpt from the Introduction
I could hear another boat approaching, to the south, near the seamount peak. I heard the metallic trill of the anchor chain running out over the rail as the hook dropped to the seabed. A few minutes later there was the sound of scuba divers plunging into the water, and then their scratchy inhalations and bubbly exhalations -- like a team of underwater Darth Vaders. I looked across at my dive partner Luke. Maybe they would flush out the sharks in our direction this time. He seemed to be thinking the same thing. Hammerheads hate bubbles.
We had been crouched down, hunkered on the flank of the seamount, for 53 minutes, one on either side of a small ravine under 25 meters (80 feet) of water. Every so often a group of seven large hammerhead sharks would swim cautiously through the ravine. Their muscular flanks rippled languidly, reflecting a silvery light that highlighted their exquisite form and underlying power.
We had our tagging poles ready, with pop-up satellite tags that would track their migratory habits. We were diving with rebreathers -- closed-circuit scuba systems -- so we were silently inhaling the same warm air over and over, through a loop that filtered out carbon dioxide and added oxygen. The sharks didn't notice us, and neither did the divers. It was peaceful; we were simply waiting for a shark to swim close enough to attach the transmitter tags. They were just so wary in these small groups.
I wondered what it must have been like here at the Espiritu Santo seamount 20 years earlier, when the scalloped hammerhead schools were so massive you could not count all the sharks. In the three years since starting my PhD research, in 2000, I had made more than a hundred dives at this site. Most days there were only a handful of these beautiful sharks. You had to go way out to sea, to isolated islands -- Cocos, the
Revillagigedos or the Galapagos Islands -- to see those big schools now.
On the way out to the seamount from La Paz we had motored past a beach where fishermen cleaned their meager catches. There were piles of hammerhead shark heads -- tiny ones. They were from baby sharks, each no larger than my arm. It was a regular sight: baby shark heads at the tide line. As we waited at the seamount, looking across at each other, then scanning around, I wondered when a big school would come by again.
My infatuation with sharks had begun long before, but that dive was a turning point. Somehow I felt for the first time the true fragility of these creatures. It suddenly sank in that these powerful, majestic and feared apex predators were also vulnerable. Maybe it was the circumstances of the dive: sitting motionless for hours, silently watching the ocean from within. Feeling part of the reef, part of the seamount rock, witnessing ocean life as the seamount had, over a geological timescale. Watching boats come and sharks go. I thought, I should not be among the last to witness this. How much more important and beautiful a shark is in the ocean than in an expensive bowl of soup.
Sharks are beasts we love to fear. There is some essence about them that has captivated us all, a spell that was probably cast the first time a human ever encountered a shark -- legends were born. Since that first encounter, we have learned so much about sharks. We have learned of their migrations, their dietary preferences and the strange, intimate details of their reproduction. The more we learn, the more we are fascinated. We can't get enough.
But perhaps the most surprising thing we have learned is that sharks are generally in trouble worldwide. How could this be? How could our beloved demons now need our protection? What happened, and why do we care? To appreciate this we need to take a step back and consider sharks in their evolutionary context.