Chasing Shadows by Greg Skomal

Author:Greg Skomal
Language: eng
Format: epub
Publisher: HarperCollins
Published: 2023-04-20T00:00:00+00:00

Chapter 8

It Begins

As the holiday weekend approaches, we just want the public to realize sharks are in the area and to exercise caution and good judgment.

—Lisa Capone, Massachusetts Executive Office of Energy and Environmental Affairs, Labor Day weekend, 2009

AUGUST 25, 1986—43°52'09.0"N, 69°05'29.8"W (GULF OF MAINE)

The twelve-foot female white shark passes Monhegan and Metinic Islands, swimming in a northeasterly direction through the Gulf of Maine. It’s summer, and the days are long. The water has warmed from the thirties in the winter to nearly 60°F, but the shark’s internal temperature can be as high as 70°F. It’s the reason the shark can both venture here in the first place and, more importantly, hunt successfully.

As she swims, water moves into her open mouth, then flows over her five gills and out her long gill slits, allowing her to breathe. Sharks lack lungs, but like human lungs, the shark’s thin gill filaments provide for gas exchange, whereby oxygen is extracted from the water and carbon dioxide is released. Because water possesses far less oxygen than air per unit, the shark must breathe ten to thirty times more water to get the same amount of oxygen that a human would get from the air. As a large, active, and fast-swimming shark, she relies on having more gill surface area and a larger heart to collect and then pump oxygen-rich blood throughout her body. The downside to this so-called obligate ram ventilation is that she must keep swimming. Otherwise, unlike sharks that can breathe by using the muscles of their mouth to draw water in and over their gills (a process known as buccal pumping), the white shark will drown if she stops swimming.

At this point in her life, the shark is, for the first time, venturing into these higher latitudes. She spent her first several summers within the relative safety of the New York Bight, where she fed largely on ample fishes and squid in the middle of the water column or on the bottom. As the water temperature cooled in the autumn, she headed south, moving on the continental shelf to the Carolinas, where she spent the winter, feeding largely on other species making the same migration.

But changes in her body over time have prompted changes in her behavior. She is larger now, and thick body walls acts like insulation surrounding her internal furnace, allowing her to move farther north. She now has ventured northeast along the coast of Long Island, past Block Island Sound, east along the southern shores of Martha’s Vineyard and Nantucket Islands, and then north along the Outer Cape and finally into the Gulf of Maine. It is here where, like her ancestors, she is learning to hunt seals along the rocky coastlines.

As she passes inshore of Little Green Island and enters Penobscot Bay between Owl’s Head and Vinalhaven, something attracts her attention. She’s unfamiliar with exactly what it is. A scent? A vibration? The waters of Penobscot Bay are warmer than the Gulf of Maine but colder than the New York Bight.

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