Rt€@lll

MANIS RELATION TO THE REEF
-95
Inadequaey of reefs to sustain larqe-scale exploitation
. .ln:pite of their high rates of productivity, coral reefs +pear to be unable to sustain
exploilation on a .significantly large scale such as a commeicial fishery. This may be
attributed to the physical seLting of reefs in rhe Pacific, as well as to the nature of the
coral reef ecosystem.
Many islands are actually the tips of srbmerged mountains, so that the pnoductive
shallow waters are limiLed to the na*ow band which is the corel reef (Johannes, L97g).
Offshore waters tend to be hazardous . and even less produclive. In the case of atolls,
shelLered lagoons which are rpre accessible to local fisherrnen are less productive than the
more exposed reefs. This is in striking contras! with the continental situation where wide
continental shelves lend themselves to the harvesting of considerable biomass.
The nature of lhe coral reef ecosystem is zuch that it is fragile and easily disturbed
whe_n pushed beyond its limits Oahl and Baumgart, l9S2). In additi'on, it is felt that coral
reefs have low standing crops of exploitable splcies (Smith and Stimson , IgTg). ffris rnay Ue
due Lo the cryptic nature of much of the reef fauna, and the lack of extensive beds of filter
feeders that are amenable !o eurrently employed harvesting techniques. In addition, the
e.xceptionally high diversities characteristic of coral reefs'preclude the development of
sing,le, dominant speeies stands which are easily harvested. Ii would therefore appear that
reef species may suslain local (i.e. zubsistence) consunption, but not consunption greatly
exceeding this level. Subsistence exploitaLion of reef resources may thus be near the cirryini
capacity of the ecosystem, having taken millenia to adjust.
Gri99 (1979) takes a somewhat differenl view of the limitations of neef nesources but
arrives at much the same conclusion. He maintains that reef processes favor the accumulation
of biomass which results in an apparent abundance of resources, but certain characteristics
of the ecosyslem renden the latter vulnerable [o oven-exploitaLion. These characteristics are
summarized as follows:
l) Since a majority of the nutrients in the system are present in the form of biomass, a large
fraction is exposed to removal by exploitation;
2) Rernoval of nutrients from the system reduces the amount that can otherwise be recycled,
and thereby reduces potential or future production;
j) Great longevity exposes many year classes to exploitation; and
4) Lmg-lived species are characterized by low rates of turn-over.
In island settings, additional factors contribute to the easy depleLion of reef resources.
These are the small size of many islands, and the semi-enclosed character of reef ecosystems
(Grig.g, L979)- Grigg postulates lhat suslained harvests may not be much greater than l0% of
standing crops.
Varyino deqrees of dependence on reef resources
No data are available at present m the fraction of the world population living close to
and dependent m coral reefs. salvat (l9sla) estirnaLes it to be well'below 100 million. Among
the Pacific islands at presen!, there exists a spectrum from $bsistence economies to those
that are hiqhly urbanized and induetrialized. There may be found a contrast, therefore,
between self -suff icieney or a close relationship with existing terrestriel and marine
resourcesr and varying degrees of dependence on imports and wor-ld markets (Mason, L;igi
ExryP.t for the larger islands of Melanesia, however, ieefs and lagoons may oe considered the
traditional sources - of protein food (Elliott, LgTt). In Guair, marine resources have
treditionally been of. great eco-nomic significance though the subsistence base in the past hes
been agriculture rather than fishing (Nolan, LgTg). lf nray be surmised thst npst of these
marine resources are drawn from the reef and rclated ar""r, in Guam and elsewhere, because
the knowledge and technology to harvest reef resources is well within the current
capabilities of Micronesian fisherrnen, which is not the ease for pelagic fieheriea (:*rennes,
r977),