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Studies leading to determination of the status of the resource are rare. Various authors give statements that point to resource depletion as a result of uncontrolled exploitation. Some examples are given hereunder. In their review
paper, Stensland et al. 1998 express an urgent need for the status assessment of marine mammals. Newton et al. 1993 note that gastropods e.g. cowries which have commercialvalue because of the shell trade are over-
exploited. The cetaceans are apparently not commercially exploited in Tanzanian coastal waters, but populations of both dugongs and marine turtles are exploited and these animals are regarded as endangered Howell, 1988b.
Based on interviews conducted in Bagamoyo, Mgaya et al. 1999a reported that sea cucumber stocks are declining and that collectors are now employing SCUBA equipment, thus depleting the resources further.
6.7.3 Human impacts
There is some information of qualitative nature on human impacts on resources and habitats. Bryceson 1981 reviewed some anthropogenic impacts e.g. sand mining, dynamite fishing on marine habitats and resources and
builds a rationale for their conservation. Howell 1988a discusses human impacts, particularly habitat destruction e.g. deforestation and dynamite fishing and pollution e.g. oil spills on coastal seabirds. Chemical pollutants
such as petroleum products in the water may interfere with olfaction in marine turtles, which may be used in navigation and orientation. Turtles are especially vulnerable to pollutants because many feed on invertebrates,
which concentrate various pollutants Howell, 1988b.
Stensland et al. 1998 present an argument for the need toprotect marine mammals from destruction emanating from human activities particularly fishing and marine pollution. Khatib 1998 lists several anthropogenic impacts
on sea turtles around Unguja Island.
Generally, seaweed farming is considered to have mild environmental impacts, but Johnstone and Ólafsson 1995 reported that the activity has a clear effect on both benthic microbial processes and meiofauna populations. For
example, they showed that attached algae vibrated in the current thus brushing against the benthos, consequently preventing consolidation of any micro-algal mats. Ólafsson et al. 1995 suggested that seaweed farming had a
negative effect on the abundance of meiobenthos, mainly through increased predation by benthic feeding fish and the mechanical disturbance of the sediments. Mtolera et al. 1992 noted that unselective farm clearance
weeding through removal of sedentary animals, seagrasses and other seaweeds is likely to affect the benthic communities.
6.7.4 Natural impacts
Natural impacts on the resources reported here include storms and beach erosion. The latter event can lead to reduction in size or complete disappearance of an island as has been the case with Maziwi Island. The extent of
the impact resulting from submergence of the island on populations of Green Turtle that were nesting at Maziwi Island has not been determined.
6.8 Scientific and management recommendations
6.8.1 Scientific recommendations
In a study on the farming and physiology of Eucheuma, Collén et al. 1995 recommended that •
Eucheuma plants be grown at medium densities,
• Extensive farms should be discouraged to avoid Ice-Ice disease, and the stressed condition of Eucheuma, and
to reduce the negative impact of Eucheuma on other marine flora and fauna.
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In order to improve our understanding of the coastal resources, Semesi et al. 1998 proposed the following recommendations:
• Government fisheries data collection should be improved, and research and monitoring be strengthened;
• Interdisciplinary research that involves government officials and local communities should be practised;
• Scientific information collected by research institutions must be transmitted to resource managers.
6.8.2 Conservationprotectionrestricted use
Howell 1988b made the following suggestions with regard to marine turtle conservation: •
Imposition of a ban on the commercial trade of tortoiseshell; •
Introduction of awareness raising campaigns that marine turtles are endangered and must not be killed; •
Introduction of tighter enforcement of existing legislation and a ban on all individual exportation of chelonian carapaces and scales;
• Inclusion into National Nature Reserves or parks, areas of concentrated breeding.
Regarding conservation of coastal waterbirds, Howell 1988a recommended i conducting biological surveys to determine the status of the resource, ii prevention or reduction of habitat disturbance and destruction, iii
establishment of Nature Reserves, and iv education and publicity.
Since little is known of the role of sea cucumbers and molluscs in the ecosystems, Mgaya et al. 1999 recommended that sales of shells and beche-de-mer should be reduced until sufficient data on the ecology and
population dynamics are known.
6.8.3 Local awarenessparticipationtraining
Research that targets at among other things, educating resource users on the importance of conservation of the resource must ensure their active participation as holders of indigenous knowledge and skills. It is crucial that
local knowledge is documented as soon as possible in order to build a broader base for future management.
Creation of awareness at all levels of ecosystem functioning, threats, and values, policy changes, etc. is necessary. Semesi et al. 1998 suggested that local communities should be made aware of the legislative process and
opportunities for its use. Moreover, there is a need to provide translated educational materials, and to prepare films on the major habitats and resources.
6.9 Information gaps
