INTRODUCTION
Guam’s greatest
natural asset is the sea around it. The ocean provides the
people of Guam with food and recreation, with resources for economic
development, and with an environment of unexcelled natural beauty.
Those who have spent their lives on Guam sometimes take
the ocean around them for granted and may be unaware of its importance
to their daily lives. Visitors often do not have the time
or opportunity to appreciate fully the diversity and complexity
of the tropical marine environment which surrounds and supports
the island. The purpose of this book is to enable the people
of Guam, both long-time residents and short-term visitors, to
become more aware of one of the most interesting and important
components of the marine communities around Guam, the fishes.
ZOOGEOGRAPHY
Guam is located in the
tropical western Pacific (see inside back cover). It is the southernmost
and largest island of the Marianas chain, an archipelago of 15
islands which extends some 500 miles in a north-south direction
from 12° 40' N to 20° 40' N latitude. Guam’s
location places it within the Indo-West Pacific region, an area
stretching throughout the tropical zone from east Africa across
the Indian Ocean and out into the Pacific to include the island
areas of Melanesia, Micronesia, and Polynesia. The Indo-West Pacific
region is recognized by zoogeographers (scientists who study patterns
of animal distribution) as being the area richest in number of
fish species of any in the world. At present, 794 species of inshore
marine fishes are known from Guam and nearby waters. This
is considerably fewer than the estimated 2000+ species known from
the Philippines, near the center of the Indo-West Pacific region,
but significantly more than the 442 inshore species known from
Hawaii, at the periphery.
In addition to mapping
the distributions of animal species, zoogeographers have attempted
to explain how these species came to be where they are. Older
theories have assumed that most Indo-Pacific marine species have
originated in the area of the Philippines, Malaysia, and Indonesia
and from there have spread outward throughout the region. Recent
studies, however, have suggested that movements of the earth's
crust, through the process of plate tectonics, may have been important
in the distribution of inshore marine fishes. All but a
few species of Guam's fishes have widespread distributions throughout
the Indo-Pacific region, and only two species are known only from
the Marianas. These two endemic species may have evolved
in the Marianas, or they may be the last remaining populations
of once more widely distributed species.
ECOLOGY
The marine fishes of
Guam occupy three different, but interrelated, ecosystems: the
coral reef ecosystem, the deep benthic (sea bottom) ecosystem,
and the pelagic (open ocean) ecosystem. By far the greatest
number of fish species is associated with the coral reef, in large
part due to the structural complexity and zonation patterns of
this ecosystem (Figure 1). The
pelagic and deep benthic ecosystems are more uniform, with rather
broad patterns of zonation, and contain relatively few species
of fish, although those fish that do occur in these two ecosystems
are of great
