FAO Fisheries Circular No. 920 FIRM/C920
REVIEW OF THE STATE OF WORLD FISHERY RESOURCES: MARINE FISHERIES
Marine Resources Service,
Fishery Resources Division,
FAO, Rome, Italy
8. WESTERN INDIAN OCEAN
FAO Statistical Area 51
The Western Indian Ocean area (Figure B8.1) has a surface area of ~30 million km2 and encompasses regions with greatly differing fishery resources characteristics. The Northwest Arabian Sea contains areas of nearly continuous upwelling (off the Oman coast) and thus extremely high productivity as well as areas with seasonal upwelling also resulting in periods of high productivity as off the coast of Iran and Pakistan in the Gulf of Oman and Arabian Sea. This monsoon-induced upwelling extends to the west coast of India. The Persian Gulf, a shallow enclosed area characterized by warm saline waters has fisheries characteristic only to that area while in the Red Sea, narrow continental shelves and an enclosed nature also create unique fisheries situations. The Gulf of Aden and Somali coast are also monsoon-driven upwelling areas that experience seasons of high productivity. Area 51 also contains some small oceanic islands, The Seychelles, Mauritius and the Comoros, that have their own characteristic fisheries reflecting their oceanic or near-oceanic character. Further to the south, South Africa has fisheries of a temperate and sub-Antarctic nature.
Of major interest in this area is the start of a long anticipated meal fishery for myctophids (Benthosema pterotum) in the Gulf of Oman and Arabian Sea (see Special Topic section: "Lanternfish: A Potential Fishery in the Northern Arabian Sea?"). The development of this fishery raises a number of yet to be answered questions, such as the importance of this resource to other components of the ecosystem, especially the large migratory scombrids, and the existence of the stock or population structure of this species in its potential fishery area. With the advent of peace in Eritrea, exploitation of the marine resources of that country is becoming regulated, and a start is being made at developing formal management procedures. This process has still to start in the waters of Somalia, though fishing effort is reported to be high due to both 'approved fishing activities' and those of completely independent operators.
PROFILE OF CATCHES
|Figure B8.2||Figure B8.3|
These resources include Indian mackerel and various clupeoids and pelagic
percomorphs (Figure B8.3). The recent decline
in pelagic percomorphs is largely due to declines in the Persian Gulf and
Gulf of Oman, where the species form the basis of the most important commercial
fishery in the area. In contrast, the catches of demersal species, almost
entirely from ISSCAAP Group 33 (redfishes, etc.) have increased relatively
steadily since 1950, with particularly large increases since the early 1980s
coming from various species of croakers and drums (Figure
|Figure B8.5||Figure B8.6|
RESOURCE STATUS AND MANAGEMENT
Eastern Arabian Sea: Pakistan, India and Sri Lanka
The enormous number of small fishing vessels in this area makes monitoring of stock status and implementation of fisheries management measures difficult. Almost any form and size of fish that can be caught is saleable. Given the scarcity of alternative employment, fishing intensity will remain high, increasing whenever the catch rates and economic conditions will allow it to do so. Small-scale shrimp fisheries are important in both Pakistan and along the west coast of India. Gear restrictions are few and the size and range of fishing effort creates major difficulties for management.
The Persian Gulf and Gulf of Oman
Fisheries have been important in this area since ancient times, both for subsistence purposes and trade. The pearl fishery of the Persian Gulf has been famous in the past, though it is now continued at a fraction of the level of former times. Rising incomes and the traditional popularity of fish as a dietary item have resulted in virtually all resources of the area becoming fully exploited, one exception being the Indian round herring, mainly because of lack of consumer preference. The fisheries of today are carried out by motorized dhows and sambuks, smaller wooden vessels and industrial-style trawlers. These are found in most countries of the region, the exceptions being the United Arab Emirates, where trawling has been banned, and Iran, which has severely limited the ability to use trawlers inside the Gulf to a shrimping season.
The Persian Gulf itself is characterized by high-temperature highly saline water, which enters from the Gulf of Oman forming an counter-clockwise gyre then exiting as a submerged, denser warmer and saline water mass moving towards the centre of the Indian Ocean. The Persian Gulf is shallow, deeper on the Iranian side and fringed with extensive coral areas on the Arabian side. Around the Gulf of Oman the continental shelf is extremely narrow, and fisheries concentrate on pelagic species, which in the last decades has increasingly meant the medium-sized pelagics such as Scomberomorus spp. and various species of tunas.
Past conflicts in the area (the Iran-Iraq war and the invasion of Kuwait) have had severe impacts on recent fisheries, not least because of disruption of fishing activity but also because of environmental effects arising from oil pollution, or at the time of the invasion of Kuwait, from the shadowing and pollution caused by burning crude oil wells.
Three key resources of concern in the area are those of Spanish mackerel, shrimp (various Penaeid and Metapenaeid species) and the various percid fishes. Useful information on the fishes is difficult to glean because of the quality of statistics in some countries and the practice of reporting data in a highly aggregated manner. The available catches data suggests that most groups of fish species are fully exploited. The trend in catches of the perciform group is probably the best indicator for stock status in the region, because the majority of species in the perciform group are commercially fished. The catches in the perciform group dropped for two years in a row (10.2% between 1993 and 1994) and are now some 53 000 t below the levels of 1992. Catches of invertebrates are still below the 1987-88 peak (the decline largely coming from a drop in shrimp catches by Oman) but have been increasing since 1991. This recent increase may be the sign of recovery.
The Red Sea and Gulf of Aden
The Red Sea and to a lesser extent, the Gulf of Aden, being ancient sea ways have also been, at least regionally, important for their fisheries. However, the oligotrophic nature of the Red Sea, a body of water surrounded by countries with narrow continental shelves and coral outcroppings, means that fisheries, while significant locally, are not important in global terms. Several coastal states have had regionally important shrimp fisheries, particularly Saudi Arabia and the Yemen and, to a lesser extent, Eritrea. As with similar tropical areas, the fisheries resources can be characterized as those associated with coral reefs, small pelagics fisheries and those for the larger more mobile scrombroids, including some tunas. Where possible, trawl fisheries are carried on, generally using trawls with extremely small mesh in their codends, taking a wide variety of perciform fishes. With the exception of some small pelagic resources, the status of the different resources may be assumed to be fully exploited.
In the Gulf of Aden, large industrial fisheries using 'distant water' factory trawlers based in the area have exploited demersal and small pelagic fish resources in the past, but because of lack of profitability have not been functioning for some time. The situation in Somalia remains confused with informal reports of many small fishing companies starting operations and also high levels of illegal fishing, particularly outside of the Gulf of Aden.
With the coming of independence to Eritrea, this country has been renewing efforts to develop its marine fisheries. Licencing agreements had been reached with Egypt for trawling operations by that country's vessels. Fishermen also continue to land catch into Yemen which could result in misrepresentation in the reported landings for both countries.
No explicit recent stock assessment based information is available for this area, and the use of catches data as an indicator of state of exploitation is compromised because the FAO fisheries data base aggregates data from Saudi Arabia for both the Red Sea and Persian Gulf. However, the available data show clearly that the rate of increase in catches by regional countries has declined sharply during the 1990s and that catches have been effectively constant over the last few years. No species or species group has shown significant increases in catches, while catches of certain species are now well below the peak levels seen in earlier years (although, in some cases, this might be due to changes in market conditions as noted below). More detailed analysis of the data is unjustifiable because of the high level of 'estimated' landings for these countries and changing patterns in disaggregation of the data. Increases in different categories appear to be best explained by increased disaggregation by species in the reported figures.
The small areas available for trawling and absence of any effective regulation in many areas of the Red Sea probably result in fisheries that are quickly fully exploited or overexploited. Markets for fish in the area are strong, particularly in the Yemen and Egypt and for higher-priced species in Saudi Arabia. Low market demand for small pelagics has resulted in reduced fishing for these species, particularly with the withdrawal of East European operators who supplied home markets. This fishery appears to have ceased at the beginning of the 1980s.
Coastal East Africa (Somalia to Mozambique)
The East coast of Africa represents a wide range of oceanographic environments and the western Indian Ocean is the site of some of the most dynamically varying large marine ecosystems in the world. The Somali Current develops during the southwest monsoon to become the fastest open-ocean current in the world. The coastal upwelling that occurs along the African coast during the intensified phase of the Somali Current is the most intense large-scale seasonal coastal upwelling system in the world. Other nearby regions are also strongly influenced by the annually reversing monsoon regime. However, the region is also uniquely puzzling because the coastal fish production seems minuscule for such a large area. The coastal fishery yield along the entire western boundary of the Indian Ocean, including the various island states of the western half of that ocean, represents less than one percent of the global landings. In spite of this, most of the coastal fish stocks of the region are considered to be fully exploited or overexploited.
Coastal fisheries production usually far outweighs production from oceanic species such as tunas and generally constitutes around 90-95% of total landings, but in the southwestern Indian Ocean the contributions of coastal and oceanic fisheries are approximately equal. The Indian Ocean continental shelf of Africa is relatively narrow, and this might provide some explanation for the low coastal landings. However, the disparity in continental shelf area compared to other ocean regions is far less drastic than would be necessary to adequately explain the above anomaly in fish production.
While the coastal fisheries are harvested mostly by coastal states, the more lucrative oceanic fisheries are harvested mostly by distant-water fishing fleets from Europe and eastern Asia. Even so, and despite the low coastal landings, fishing and its associated economic activities are often extremely important to local economies. In some of the southwestern Indian Ocean countries, fish are nearly the sole source of animal protein available to the local populations. Moreover, in a region faced with chronic scarcities of foreign exchange, exports of fishery products represent vital sources of exchangeable earnings. The shrimp fishery on the Sofala Bank contributes up to 40% of Mozambique's foreign exchange, despite seemingly low landings (<10,000 t).
While total landings in 1995 were relatively high, (7 344 t), the largest since 1986, yield per recruit analysis indicates that nearly the same level of catch could be taken with about 30% less fishing effort. In addition to cost-related improvements in economic efficiency and performance, the higher shrimp biomass associated with lower effort levels reduces the risk of recruitment failure (and may result in increased recruitment) and results in greater average size of landed shrimp. Since larger shrimp fetch a higher price per unit weight than smaller individuals, the increases in total revenue will be greater than the increases in quantity landed. Shrimp catches are also one of the most important components of landings in Madagascar because of their importance to foreign exchange earnings. Landings in 1995 were marked by a reduction of 16% to 7 623 t, of which a small increase had been registered in the artisanal catch, from 188 t to 283 t. The average catch rate was 576 kg/day. Landed bycatch represented 45% of landings; a total of 3 445 t of fish were landed by the shrimp trawlers. This was a 27% increase over 1994.
Landings by regional countries in the area have stagnated somewhat since the 1990s. Many of the reported catches are not identified to species (42% in 1994), preventing an analysis of resource status at species level. However, there does not appear to have been any reductions in fishing effort and thus the relative constancy of catches indicates that the resources exploited by regional countries may be "fully" exploited. However, reported catches by distant-water fishing nations have increased dramatically through the 1990s (from ~325 000 t in 1990 to ~430 000 t in 1993 and ~400 000 t in 1994), with Spain and France together accounting for over 50% of these catches.