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This article reviews the governance and management of Marine Protected Areas (MPAs), and the coral reefs they contain, in the eastern African Region. This includes the Comoros, Kenya, Madagascar, Mauritius, Mozambique, Tanzania, and the Seychelles. Three generations or categories of MPAs are distinguished: i) small areas for protection of a single species or unique marine habitat; ii) large multiple use MPAs designed for coastal development as well as biodiversity protection; and iii) MPAs managed by a nongovernmental organization (NGO) or the private sector. Each of these MPA types is examined according to the policies, legislation, and management systems they entail as well as the economic and community situation they operate within. The paper also provides a review of some eastern African MPAs in terms of their size and location, the type of MPA, zonation schemes, and financial status. The successes of the different types of MPAs are discussed based on specific indicators, such as changes in biodiversity, infrastructure, compliance to regulations and the level of involvement of primary stakeholders in the management. From the review it is clear that a fourth generation of MPAs may be forthcoming; community-based MPAs. Although lack of data makes it difficult to assess the effectiveness of these different categories of MPAs, it is clear that no MPA can succeed without support of the local communities. Generally, the results of the analysis are promising for MPAs, however a lack of data is hampering a deeper analysis. The major issues facing MPAs in the region are highlighted, as well as some regional initiatives striving to address these issues. A number of recommendations are made, aiming to strengthen the establishment and management of MPAs in the eastern African region.
Coastal resource utilization and management systems, both traditional and more recently conceived, were studied in Mecúfi district, northern Mozambique in a post-conflict situation prior to which a significant migration of people to the coast had occurred. A wide variety of coastal biotopes containing a multitude of resources had been affected in various ways. Intertidal organisms exhibited signs of decreasing abundance and average size, whereas offshore fishes and mangrove forests did not show signs of overutilization. It was observed that traditional coastal management systems were still influential, but that newer initiatives were only beginning to enter into significant dialogue and cooperation with these. In the current circumstances of peace and political stability, the principal threat to coastal management and the interests of local people in Mecúfi is considered to be potential loss of common property resources and land tenure in the face of prospects of privatization, but Mozambican authorities are presently addressing these issues with legal reforms.
Fishery resources are a vital source of food and make valuable economic contributions to the local communities involved in fishery activities along the 850 km stretch of the Tanzania coastline and numerous islands. Small-scale artisanal fishery accounts for the majority of fish catch produced by more than 43 000 fishermen in the country, mainly operating in shallow waters within the continental shelf, using traditional fishing vessels including small boats, dhows, canoes, outrigger canoes and dinghys. Various fishing techniques are applied using uncomplicated passive fishing gears such as basket traps, fence traps, nets as well as different hook and line techniques. Species composition and size of the fish varies with gear type and location. More than 500 species of fish are utilized for food with reef fishes being the most important category including emperors, snappers, sweetlips, parrotfish, surgeonfish, rabbitfish, groupers and goatfish. Most of the fish products are used for subsistence purposes. However, some are exported. Destructive fishing methods such as drag nets and dynamite fishing pose a serious problem as they destroy important habitats for fish and other organisms, and there is a long-term trend of overharvested fishery resources. However, fishing pressure varies within the country as fishery resources are utilized in a sustainable manner in some areas. For this report more than 340 references about Tanzanian fishery and fish ecology were covered. There are many gaps in terms of information needed for successful fishery management regarding both basic and applied research. Most research results have been presented as grey literature (57%) with limited distribution; only one-fifth were scientific publications in international journals.
Preliminary results for the artisanal fisheries of Octopus cyanea Gray (1849) in Tanzania are provided for the period April 2000 until June 2001. A total of 2546 individual catches and 15473 specimens were analyzed from 3 sites located at Tanga, Mafia Island, and Mtwara. Size range, average weight and catch per unit effort (CPUE) were all significantly lower at Tanga and Mtwara compared to Mafia indicating that the former sites may be overfished. Abundance of smaller individuals was higher at Tanga and Mtwara, but overall biomass was lower. Octopi at each site exhibited allometric growth as indicated by analyses of the length-weight relationships. Females become sexually mature at a minimum weight of 600 g while for males the minimum weight was 320 g. Higher numbers of mature individuals were found in June of both years and correlate with peaks in the gonosomatic index. Recruitment peaked a few months after brooding periods. Sex ratios indicate females may be more prone to capture during brooding periods. Reasons for differences between sites are discussed.
This paper reviews the experience and status of coastal aquaculture of seaweeds, mollusks, fish and crustaceans in eastern Africa and the islands of the western Indian Ocean. In many respects, coastal aquaculture is still in its infancy in the region, and there is a pressing need to formulate development strategies aimed at improving the income and assuring the availability of affordable protein to coastal communities. This paper also draws from positive and negative experiences in other parts of the world. The requirements of feed and fry, and the conversion of mangroves are used to illustrate how some aquaculture activities constitute a net loss to global seafood production. The paper presents both general and specific sustainability guidelines based on the acknowledgement of aquaculture as an ecological process. It is concluded that without clear recognition of its dependence on natural ecosystems, the aquaculture industry is unlikely to develop to its full potential in the region.
Data were collected in southern Kenya on coral reef ecosystems and fisheries to assess the influence of the 1998 coral bleaching and mortality event. We compared benthic cover, sea urchin and fish abundance in unfished marine parks and fished reefs and the reef-associated fisheries 3 years before and after 1998. Hard and soft coral decreased while coralline algae increased in both management areas. Turf increased in marine parks and sponge and fleshy algae increased in the fished reefs. Sea urchin grazer biomass was unchanged over this period and the fish community changed less than benthic cover. In general, butterflyfish, damselfish and wrasses were negatively influenced while surgeonfish and a few uncommon families were positively influenced by the substratum change. There was a 17% increase in fishing effort as measured by fishermen per day at each landing site and the total demersal catch declined by 8% and the catch per man declined by 21% after 1998. The decline in the total catch and CPUE combined with the increase in effort suggest an overexploited fishery and this makes it difficult to distinguish changes caused by coral mortality or fishing effort. The price of fish increased over this period and this caused an 18% increase in the total value of the fishery but no difference in the net income of individual fishermen.
Coral recruitment, following the coral bleaching episode in 1998, was studied on the Kenyan coast. Scleractinian recruits representing 31 genera from 13 families were recorded in 2001, the dominant families at all sites being the Pocilloporidae, Poritidae, and Faviidae. The highest diversity and density of scleractinian recruits was observed at a site located within a marine park, with 11 families, 20 genera and 21.4 recruits per m2, while an unprotected site and sites with higher sediment input showed recruit densities under five. Survivorship was generally higher in massive than in branching genera. The diversity in the recruit population has decreased compared to pre-bleaching levels, while no significant change in density was recorded. Growth rates in recruits were consistent between sites and time of year, with an average growth rate of 0.117 mm2 mm−2 mon−1, with variation between species. The fastest growing genera were Echinopora, Acropora, Pocillopora, and Porites. With the exception of Montipora, the growth rate of surviving pre-bleaching colonies was lower and exhibited greater variability between taxa and sites than among recruits.
This study examined the distribution and abundance of corallimorpharians (Cnidaria, Anthozoa) in Tanzania in relation to different aspects of the coral reef environment. Five reefs under varying degrees of human disturbance were investigated using the line intercept transect and point technique. Corallimorpharian growth and the composition of the substratum were quantified in different habitats within reefs: the inner and middle reef flat, the reef crest, and at the 2 and 4 m depths on the reef slope. Corallimorpharians occurred on all the reefs and 5 species were identified: Rhodactis rhodostoma, R. mussoides, Ricordea yuma, Actinodiscus unguja and A. nummiforme. R. rhodostoma was the dominant corallimorpharian at all sites. Within reefs, they had the highest densities in the shallow habitats. While R. rhodostoma occurred in all habitats, the other corallimorpharian species showed uneven distributions. Corallimorpharians ranked second, after scleractinian coral, in percent living cover. Results from this study suggested that corallimorpharians benefitted from disturbance compared with other sessile organisms. They preferred inhabiting areas with dead coral, rock and rubble whilst live coral was avoided. There was a positive relationship between percent cover of corallimorpharians and water turbidity and they dominated the more disturbed reefs, i.e. reefs that were affected by higher nutrient loads and fishing.
The structure and regeneration patterns of Mida Creek mangrove vegetation were studied along belt transects at 2 forest sites of Mida Creek (3°20′S, 40°00′E): Uyombo and Kirepwe. Based on the species importance values, the dominant mangrove tree species in Mida were Ceriops tagal (Perr.) C. B. Robinson and Rhizophora mucronata Lamk. Tree density varied from 1197 trees ha−1 at Kirepwe to 1585 trees ha−1 at Uyombo and mean tree height was higher at the former site compared to the latter. The size-class structure at both localities of Mida showed the presence of more small trees than large ones. Spatial distribution pattern of adults and juveniles varied greatly between sites and they showed a close to uniform pattern (Morisita's Index I0 ≪ 1) for trees, but a tendency to random distribution (I0 = 1) for juveniles. The present paper shows that unmanaged but exploited mangroves do not necessarily disappear, but change qualitatively from locally preferred R. mucronata to the less preferred C. tagal. Whereas the effects of this change on the ecological function of the mangrove cannot be estimated yet, the economical function of the mangrove has evidently weakened.
Leaf litter removal by the abundant mangrove decapod crab Neosarmatium meinerti was studied in series of field and laboratory experiments in East Africa. In the high intertidal Avicennia marina zone crabs buried all leaves placed on the forest floor and consumed on average 67% of them within 2 hrs. High shore crabs in Kenya buried 4 g m−2 leaf-litter in 1 hr, i.e. approx. twice the daily litter fall. In contrast, in the low shore Sonneratia alba zone, where typical leaf-eating crabs were absent, none of the offered leaves showed signs of herbivory. Leaf choice experiments in the laboratory showed that N. meinerti preferred some species to others. Leaf consumption per gram crab was higher in females than males. The laboratory studies also indicated that crabs could consume substantially more than the average daily litter fall. Video recordings documented frequent fights to gain or retain fallen leaves, suggesting strong competition for leaf litter. Earlier studies indicating that N. meinerti may sweep mangrove forest floors clean of leaf litter are confirmed. In high shore mangroves of East and South Africa where N. meinerti is common, energy flow appears unique: virtually all litter production is retained
Field surveys were conducted to evaluate the occurrence of the isopod borer Sphaeroma terebrans (Crustacea) in aerial roots (prop roots) of the red mangrove Rhizophora mucronata on several different spatial scales (m to 100 km) in East Africa. In 6 out of 17 sites studied in Kenya and on Zanzibar Island, Tanzania, no signs of the isopods were found. When the isopods were present the frequency of infestation was high. Trees in muddy substrates in the lower intertidal, in particular at fringing channels or the open sea, showed high prevalence and intensity of infestation, with large part of their roots damaged or dead. Trees at the upper range of Rhizophora, in sandy and muddy areas, showed no signs of isopod infestation. This pattern recurred in mangrove forests on large spatial scales and there was no indication that island forests differed from the mainland forests. This indicates that sediment characteristics, vertical height in the tidal zone, and direct exposure to incoming water are the major factors controlling the abundance of S. terebrans. The isopod may play an important role in determining the lower intertidal limits of R. mucronata. Trees with numerous dead or nongrowing roots, as result of Sphaeroma attack, are likely to tumble due to a lack of root support and this is most likely to occur along channels at the lower, muddy intertidal. Tumbled trees were frequently observed along channels in the lower, muddy intertidal, but rarely in the mid or high intertidal. Implications for management of mangrove forests are discussed.
This study focuses on sediment exchange dynamics in Mwache Creek, a shallow tidal mangrove wetland in Kenya. The surface area of the creek is 17 km2 at high water spring. The creek experiences semidiurnal tides with tidal ranges of 3.2 m and 1.4 m during spring and neap tides, respectively. The creek is ebb dominant in the frontwater zone main channel and is flood dominant in the backwater zone main channel. During rainy season, the creek receives freshwater and terrigenous sediments from the seasonal Mwache River. Heavy supply of terrigenous sediments during the El Niño of 1997–1998 led to the huge deposition of sediments (106 tonnes) in the wetland that caused massive destruction of the mangrove forest in the upper region. In this study, sea level, tidal discharges, tidal current velocities, salinity, total suspended sediment concentrations (TSSC) and particulate organic sediment concentrations (POSC) measured in stations established within the main channel and also within the mangrove forests, were used to determine the dynamics of sediment exchange between the frontwater and backwater zones of the main channel including also the exchange with mangrove forests. The results showed that during wet seasons, the high suspended sediment concentration associated with river discharge and tidal resuspension of fine channel-bed sediment accounts for the inflow of highly turbid water into the degraded mangrove forest. Despite the degradation of the mangrove forest, sediment outflow from the mangrove forest was considerably less than the inflow. This caused a net trapping of sediment in the wetland. The net import of the sediment dominated in spring tide during both wet and dry season and during neap tide in the wet season. However, as compared to heavily vegetated mangrove wetlands, the generally degraded Mwache Creek mangrove wetland sediment trapping efficiency is low as the average is about 30% for the highly degraded backwater zone mangrove forest and 65% in the moderately degraded frontwater zone mangrove forest.
Seagrasses are marine angiosperms widely distributed in both tropical and temperate coastal waters creating one of the most productive aquatic ecosystems on earth. In the Western Indian Ocean (WIO) region, with its 13 reported seagrass species, these ecosystems cover wide areas of near-shore soft bottoms through the 12 000 km coastline. Seagrass beds are found intertidally as well as subtidally, sometimes down to about 40 m, and do often occur in close connection to coral reefs and mangroves. Due to the high primary production and a complex habitat structure, seagrass beds support a variety of benthic, demersal and pelagic organisms. Many fish and shellfish species, including those of commercial interest, are attracted to seagrass habitats for foraging and shelter, especially during their juvenile life stages. Examples of abundant and widespread fish species associated to seagrass beds in the WIO belong to the families Apogonidae, Blenniidae, Centriscidae, Gerreidae, Gobiidae, Labridae, Lethrinidae Lutjanidae, Monacanthidae, Scaridae, Scorpaenidae, Siganidae, Syngnathidae and Teraponidae. Consequently, seagrass ecosystems in the WIO are valuable resources for fisheries at both local and regional scales. Still, seagrass research in the WIO is scarce compared to other regions and it is mainly focusing on botanic diversity and ecology. This article reviews the research status of seagrass beds in the WIO with particular emphasis on fish and fisheries. Most research on this topic has been conducted along the East African coast, i.e. in Kenya, Tanzania, Mozambique and eastern South Africa, while less research was carried out in Somalia and the Island States of the WIO (Seychelles, Comoros, Reunion (France), Mauritius and Madagascar). Published papers on seagrass fish ecology in the region are few and mainly descriptive. Hence, there is a need of more scientific knowledge in the form of describing patterns and processes through both field and experimental work. Quantitative seagrass fish community studies in the WIO such as the case study presented in this paper are negligible, but necessitated for the perspective of fisheries management. It is also highlighted that the pressure on seagrass beds in the region is increasing due to growing coastal populations and human disturbance from e.g. pollution, eutrophication, sedimentation, fishing activities and collection of invertebrates, and its effect are little understood. Thus, there is a demand for more research that will generate information useful for sustainable management of seagrass ecosystems in the WIO.