A guide for planners and managers - IUCN

164 MARINE AND COASTAL
PROTECTED AREAS
Photo by R. Salm.
1.2 The Value of Coral Reefs
It is the many subdivisions of food and space resources that support the high diversity
of fishes on coral reefs (Smith and Tyler, 1972). Around the reefs, space is probably
more limiting than food. Resident reef fishes have specific shelter sites that can be
shared by diurnal and nocturnal fishes (Collete and Talbot, 1972; Smith and Tyler,
1972). During the day, many of the nocturnal fishes occupy these shelter sites, and
others hover around the reef, while the diurnal fishes are out foraging for food
(Figure II-3). At night they reverse roles and places. Many fishes leave the reef to feed
over the adjacent flats, foraging up to 100 m away (Earle, 1972). This sharing of space
allows a healthy reef to shelter two separate communities of fishes, greatly increasing
the diversity of species and number of individuals the reef can accommodate. The
standing crop of fish populations on reefs may reach 5 to 15 times the size of the crops
of productive North Atlantic fishing grounds (Stevenson and Marshall, 1974) (Figure
II-4). Further, the reefs and their surroundings may provide 5,000 kg per fishermen
per year.
FIGURE II-3.
Corals, such as this staghorn (Acropora) off Mauritius Island, offer sanctuary to humbugs (Dascyllus aruanus) and
blue-green pullers (Chromis caeruleus), among a variety of other species.
High competition with other organisms has caused species that live in crowded
conditions, such as reefs, to develop many kinds of interactions. One type of interaction
particularly well developed on coral reefs is antibiosis, the production by one organism
of substances that are harmful or repulsive to others (Burkholder, 1973). Some of these
substances are highly active biocompounds whose applications in medical research
are just now being discovered. For example, certain reef-dwelling sea fans and