72
East Barbett, 1997. The trade for these resources has been present in Tanzania for centuries, Shark meat is widely consumed although it is not very popular in comparison to other species of fish. Shark jaws and teeth are
sold to tourists. Some fish is exported fresh overseas and foreign exchange is available through the export of these products. Most of the export revenue comes from shrimps. The two main fishing grounds for shrimp are around
Bagamoyo Sadani and the Rufuji Delta in South of Tanzania where about five species of shrimps are caught Semesi and Ngoile, 1993
3.6.2 Condition of the resource
The fishery resources have reached the upper level of exploitation. This is believed to be due fishermen fishing in the same areas since time immemorial due to the limitation of the range of their fishing vessels which are not
powered by motor engines and due to lack of proper management strategies. Interviews with fishermen also confirm that catches are declining. Increase in fishing effort will not increase catch rates. The total annual catch in
Zanzibar was about 20, 000t in 1988 but currently it has dropped to less than 13000t. This reduction in fish catch can also be observed in some localised areas such as in Chwaka bay Jiddawi, 1999b and for specific fish such as
the reef fisheries of Zanzibar Jiddawi, 1998.
There are some resources, which have been affected more than others. For example in the Zanzibar the small pelagic fisheries, the catch has drastically decline from 600t in 1986 by the Zanzibar fisheries cooperation boats to
91t in 1997 Jiddawi, 1999a. The history of the purse seine fishery has been documented in a video produced by Jiddawi 1996 under the Marine Education and Extension Development Unit at the Institute of Marine Sciences,
Zanzibar. Fish resource assessment surveys conducted in the 1970s Birkett, 1978 and in the 1980s Iversen, et al
., 1985 gave estimates of the standing stocks for coastal water ranging from 94,000t to 174,000t. Annual yield estimates for demersal species was 38,000tyear and about 23,000t for pelagic species Ardill and Sanders, 1991.
Seashells and sea cucumbers are overexploited along the whole coast due to rampant collection. There have been no population studies of any of the commercially exploited species Horrill and Ngoile, 1991. However, the
traders claim that the sizes of some of the sea cucumbers have decreased, but they still continue to buy due to competition among traders. The catch rate of the long line fisheries in most parts of the region including Tanzania,
the catch rate, in numbers and weight, has declined drastically Ardill, 1984. Shark fin trade has also declined and some fish species are rarely seen now in Tanzania waters Barnett, 1997; Jiddawi and Shehe, 1999
3.6.3 Human impacts
The demand for fishery resources has been gradually increasing with the increase in population and tourism development. This has caused an increase in fishing pressure and the use of gears that are efficient but destructive.
Most of these gears are prohibited by law Anon, 1988, 1993 but due to lack of monitoring and surveillance they continue to be used. Some of the destructive gears commonly used are dynamites, which has been documented by
several authors Chachage, 1988, Chande, 1994, Guard and Masaiganah, 1997. The use of the beach seine
Benno, 1991, Linden and Lundin, 1996, sticks, spears and juya la kigumi dragged net which smashes reefs Muhando and Jiddawi, 1998 has also been reported. This fishery is one of the most difficult to control because
the net used is not illegal, however, it is the action involved in the technique of using the net which is a problem. That is the breaking of coral reefs associated with the use of sticks to chase away hiding fish. Some fishermen also
use poison in fishing Muhando and Jiddawi, 1998. The use of such gears leads to indiscriminate destruction of the breeding and nursery grounds of fish and has seriously affected the fisheries. The fish larvae and juveniles are
killed before they grow and recruit into the fishery.
Destruction of habitats by human through indiscriminate mangrove cutting have also a negative influence on fisheries as mangrove are nursery and breeding grounds of fish. This is very common in many parts of Tanzania
as mangroves have many uses. Also, human impact is caused through building of dams. One report summaries the impact of the Stieglers Gorge multipurpose project on fisheries in Rufiji delta and Mafia Channel under the Rufiji
Basin Study Programme Atkins, 1981
73
3.6.4 Natural impacts
There is no report that describes natural calamities. However, storms and strong waves are known to damage coral reefs and indirectly could affect fish populations. Other impacts could be caused by river runoffs, which could
create siltation effects especially around river mouths. A recent event, has been that of coral bleaching caused as a result of the increase in water temperatures in 1998 due to El Nino effect. This is believed to have caused an
impact on coral reefs in several parts of Tanzania and is hypothesised to have caused a change in fish species composition Muhando pers comm., 1999. In Some areas where bleaching has occurred, Marcus 1999 observed
a shift in species composition with herbivorous fish dominating these areas Ohman per comm, 1999. A study has now been initiated to look at the impact of bleaching and other factors affecting coral reefs on fisheries and
tourism in Tanzania and the whole region in general.
3.7 Scientific and management recommendations 3.7.1
