nets used on the reef ), or by setting aside certain
areas as sanctuaries, where fish can grow to maturity and reproduce
without being subject to fishing. Management efforts designed
to maximize the weight of the fish catch by regulating the size
of adult fish which can be caught require considerable scientific
knowledge of growth rates and natural death rates of fish species.
The establishment of
marine sanctuaries within which harvesting marine organisms is
forbidden has proved to be a useful management measure in Hawaii
and elsewhere. Such sanctuaries permit populations of reef
fish to carry out their normal behaviors unmolested and are valuable
tourist attractions as well as popular spots for underwater photographers.
Often fishes in exploited areas become wary of humans, and
close-up underwater photography of many species is very difficult.
Sanctuaries also may allow fishes to spawn more effectively
and so serve to provide young recruits to other, overexploited
parts of the reef.
DANGEROUS MARINE FISHES
Although some species
of marine fish around Guam are potentially dangerous, there is
no reason to be fearful of the sea. With reasonable prudence,
fishing and swimming on the reef are safe and enjoyable. Those
fish which are hazardous are not out to get humans, but they have
evolved effective mechanisms for capturing food or for discouraging
predators, and an understanding of these adaptations will prevent
mishaps. Predatory sharks (p.
17) may be attracted by unusual sounds or by light glinting
off a shiny surface. In most cases a shark will investigate
and then swim off, but occasionally, particularly if the shark
is provoked or if it smells blood, it will attack. Although
there are many sharks in the waters around Guam, very few attacks
on humans have been reported.
Divers sometimes have
run-ins with moray eels (p.
21). These eels live in holes and crevices in the reef
during the daytime, and shell collectors or lobster fishermen
who reach into these holes may be bitten. At night morays
emerge from their hideaways and may try to take fish away from
nighttime spearfishermen.
Several species of fish
on Guam have venomous spines which can inflict painful wounds
if stepped on or handled carelessly. The most venomous are
members of the family Scorpaenidae, the scorpionfishes.
The lionfishes (p. 35)
are members of this family and are quite conspicuous, but the
stonefish (p. 35)
is well camouflaged and is difficult to spot on the reef. It
is advisable to wear footgear when walking the reef to protect
against the extemely painful, and sometimes fatal, sting of this
fish. Stingrays (p. 19)
can also deliver a powerful sting if stepped on, but they are
not particularly numerous on Guam. Although not venomous,
the cheek spines of the squirrelfish Adioryx (p.
29) and the sharp blades at the base of the tail of surgeonfishes
(p. 111) can injure
the unwary fisherman.
The flesh and viscera
of some species of f ish may be toxic if eaten. In the case
of the puffers (pp. 133–135),
the toxin is produced by the fish and is probably a means of discouraging
predators from eating them. Another