Stock assessment

Hayasi, S.

Stock assessment

Autores

Hayasi, S.

Editor

FAO ;

Descripción

Information on the Indian Ocean fishery resources is not yet extensive enough to permit estimates of maximum sustained yields for most species. Data are especially lacking for the coastal fisheries of scattered nature. 20 Among oceanic species, those heavily exploited are the large-sized tunas. The maximum sustained yields for the longline fishery are estimated to be 107,000 to 128,000 tons. The billfish catch is now reportedly around 10,000 tons by longline (Table 2). Untouched oceanic species are the small tunas and sharks at the fourth trophic level, and saury, squids, and other small shoaling pelagic forms of the third trophic level. The skipjack is the most promising species for future exploitation, estimated to provide a catch of 200,000 to 400,000 tons. Further surveys inclusive of larva collection and acoustic and experimental fishing will present more reliable estimates of the pelagic potentials. It is also possible to develop demersal fisheries on offshore banks, supposed to sustain three million tons of catch, after intensive exploratory operation. Present coastal fisheries are not intensive, except those for prawns and other valuable Crustacea (Table 17). This makes it difficult to determine levels of the maximum sustained yields or of the potential yields. Estimated potential yields, three to eight million tons in the western Indian Ocean and three to five million tons in the eastern Indian Ocean, a.re far larger than the present catches, which are about one mil lion tons in each of the two parts of the ocean (Table 18). What is needed in order to obtain more appropriate measures of the maximum sustained yields and potential yields are the collection of catch statistics and information on distribution, etc., by exploratory fishing outside the traditional fishing grounds. Prawns, especially Penaeus followed by Metapenaeus, are exploited by mechanized trawlers together with traditional gear. Heavy exploitation has already been known, at least, in the Gulf between Iran and the Arabian Peninsula, in the waters around Karachi, West Pakistan; off Kerala State in India, and in Shark Bay, Australia (Table 19). Shrimp fisheries are developing in other parts of the Indian Ocean, such as Tanzania, Madagascar, Indonesia, and Western Australia. It is urgent to collect and analyse the catch statistics and other biological information. In addition, the limited distribution of prawns in inshore waters often causes overcrowding of commercial boats therein, res ulting in intensive fishing of other fish stocks in these areas, some of which are discarded at sea, thus resulting in the waste of living resources. It is essential to prepare catch statistics and other scientific information so as to assist the industry.