Fishing mortality rates of giant clams (Family Tridacnidae) from the Sulu Archipelago and Southern Palawan, Philippines

Abstract

Average size frequency distributions of <i>Tridacna squamosa, T. gigas, Hippopus hippopus</i> and <i>H. porcellanus</i> harvested from the Sulu Archipelago and Southern Palawan areas from 1978–1985 were derived from export records and a warehouse inventory of giant clam shells. Average species mortality rates (<i>Z</i>) were estimated and were used to approximate average fishing mortality rates (<i>F</i>) over the period 1978–1985. Crude estimates of exploitation rates (<i>F/Z</i>) indicate that populations of these species are already overexploited. These findings have serious implications in view of the fact that the Sulu Archipelago and Southern Palawan are thought to be the last strongholds of giant clams in Philippine waters.