Page 9 - Fish and Amphibians (Britannica Illustrated Science Library)

VIETNAM
Along this country's nearly Water, the been in a state of crisis. In Nha Trang Bay this reason, they have developed various
200 miles (300 km) of
coastline live great the growth of outside investment in survival techniques to live in such a wide
numbers of people who aquaculture has limited the economic variety of places.
depend on fishing and
coral reefs for their Source of Life opportunities of the local population,
livelihood. including fishing for squid and other
species in the reefs with hook and line.
In other cases, commercial fishing espite the fact that lunglike sacs
he life of marine creatures is endangers the future of those who rely on evolved because of the difficulty of
fascinating and has always been traditional fishing methods to make a D breathing with gills in water with low
T closely linked to human life. This is so living. This is only one of the topics oxygen content, the development of these
particularly because fishing has been the explored in this book, which also relates in sacs was also the first step toward moving
livelihood of islanders through the years. detail many secrets of these vertebrates, onto land. Some descendants of the first fish
Yet for some time, in many areas of the which were among the first creatures with with fleshy, jointed fins, known as lobe-fin
world—such as Nha Trang Bay, on the skeletons to appear on the Earth. Perhaps fishes, began to find terrestrial food sources
south coast of Vietnam—this activity has knowing more about their habits and and, with time, adapted more completely to
modes of life may move us to care for life on the planet's surface. This evolutionary
them and protect them. They are at the change—passing from an aquatic to a
mercy of variations in water conditions to terrestrial medium—constituted a true
a greater extent than humans. revolution for the life-forms that existed up
until then. The amphibians we will show you
in this book that are living today are a tiny
representation of all those that appeared
umans have marveled for centuries at during the Devonian Period, most of which
the fact that, after journeying across became extinct during the Triassic Period.
H the ocean, salmon can find the river
where they were born. Is this navigational
ability related to the Earth's magnetic field,
sense of smell, instinct, or something else mphibians, especially some frog
that humans cannot even imagine? For those species, have become true specialists
interested in statistics, in the Yukon River in A in the art of mimicry. One of the most
Alaska and in Canada, certain tagged fascinating examples is the European tree
Chinook salmon covered nearly 2,000 miles frog, which changes color to regulate its
(3,200 km) in 60 days. Upon entering the body temperature. On warm, dry evenings
river, the salmon stop eating and utilize the the frog rests in sunny places, and its skin is
fat they accumulated while in the ocean. pale. As its surroundings become cooler, the
After laying their eggs, many of the frog darkens to absorb heat. Although
females die. Most ocean fish seek shallow, amphibians are masters of camouflage,
nutrient-rich waters in which to lay their which protects them from predators, at
eggs. That is why coastal waters and present they are the object of worldwide
estuaries are so important to the life cycle of concern because of the dramatic decline in
many species. Another oddity of these their populations. Turn the page, and you will
animals is that they have adapted to living in discover much more about the abilities of
a variety of aquatic habitats: rivers, lakes, fish and amphibians, extraordinary creatures
estuaries, coral reefs, and the open sea. For that live right next to us.