139736eo.pdf (20MB) - Japan Oceanographic Data Center

environmental stress, and subsequent loss of Zostera beds in Japan was linked to industrialisation andincreasing water pollution along the coast (NAIKAI REG. FISH. RES. LAB., 1967; NASEI REG.FISH. RES. LAB., 1974).SMALL ISLANDSOTHER CRITICAL HABITATSSmall islands, offshore of the mainland coast or oceanic islands in deeper water, are numerousin many parts of the Indian Ocean. For example there are 200 or more small coral cays and islandsalong the eastern seaboard of the Red Sea alone. Island groups of the Indian Ocean, the Maldives,Seychelles, Lakshadweep, Nocibars and Andamans, include many small coralline or volcanic islets,besides the larger islands that support human population.The smaller islands constitute significant critical habitats. Not only are they generallysurrounded by shallow water marine habitats, coral reefs, seagrass beds and mangrove stands, whichare considered critical in their own right, but the islands themselves are vital breeding and nurseryareas for animals that are of significant economic value and particular scientific and popular interest- namely seabirds and turtles.Forty-two species of seabirds breed in the Indian Ocean, almost all of these invariably onsmall offshore or oceanic islands. Of these 42, fourteen are endemic to the region (UNEP, 1985);these are:Mascarene petrelPterodroma aterriinaBarau's petrelPterodroma baru'Jouanin's petrelBuiweria fallaxAbbott's boobySula abbottiIndian cormorantPhulacrocorm fuscicollisSocotra cormorantPhulacrocorax nigrogularisJavanese cormorantHalietor nigerChristmas Island frigatebird Fregata andravsiWhite-eyed gullLams leucophthalmusSooty gullLarus hemprichiiWhite-cheeked ternStem repressaSaunder's ternSterna saundersiLesser crested ternSterna bengalensisLesser noddyAnous tenuirostrisIn the Indian Ocean the breeding of all seabirds has become increasingly impacted by man'sactivities, largely by general disturbance and habitat changes (linked to the spread of villages, holidayhomes, navigational and military installations to offshore islands), by accidental introduction ofpredators (e.g. cats and rats), and also by egg collection and taking of chicks. In the past eggs havebeen collected in small quantities by fishermen and coastal villages, and generally in a sustainablemanner; but in recent years, as a result of human population expansion and the increase in range ofmotorised fishing craft, taking of eggs and chicks has greatly intensified. The Pelicaniformes(boobies, frigatebirds, etc.) appear to have been most affected and to be in serious decline: They andtheir young are taken for food; they are especially vulnerable to human disturbance because gulls taketheir eggs when they leave the nest; and they have been excluded either by the destruction of trees usedfor nesting, or by the planting of previously treeless islands with coconuts. In Indonesia (DEKORTE, 1983) and in the centraVwestern Indian Ocean (FEARE, 1984), many islands that supportedbreeding colonies earlier in this century now either lack any breeding birds or support only greatlyreduced numbers.Smalloffshore and oceanic islands also provide important nesting grounds for all five speciesof marine turtles found in the Indian Ocean: the Green turtle (Chelonia mydas), the Hawksbill(Eretmochelys imbricata), the Loggerhead (Caretta caretta), the Leatherback (Dermochefys coriacea),and the Olive Ridley (Lepidochelys olivacea). Of these, the Loggerhead may nest predominantly onmainland beaches, but the others nest frequently, and the Hawksbill almost exclusively, on smallislands. Green and Hawksbill are the most widespread species and are the only ones breeding in180