Biophysical Survey of Mafia Island Marine Reserves

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Executive Summary Major Findings • Presence of juvenile black tip sharks (Carcharhinus melanopterus) in shallow lagoon areas at Shungimbili Island Marine Reserve (SIMR). • Green turtle (Chelonia mydas) present at SIMR and Nyororo Island Marine Reserve (NIMR). SIMR is potentially a breeding and nesting site for green turtle based on observations of turtle behaviour, and anecdotal evidence from other conservation organisations operating in the area. • Hawksbill turtle (Eretmochelys imbricate) have been recorded as present at both NIMR and SIMR. • The seagrass beds at MBIMR appear to provide a particularly rich and diverse ecosystem. Observations of invertebrates and fish present have shown high abundance of important commercial and ecological species. • The presence of an extensive octopus fishery at NIMR. • Commercial diving for Spiny Lobster (Panulirus spp.) at Mbarakuni Island Marine Reserve (MBIMR) and SIMR. • Gastropod harvest for the marine curio trade at all three reserves. • Minor settlement on Nyororo Island that is engaged in commercial and subsistence fishing as well as providing a stop off for trading, and a safe haven for passing vessels. • Rapid coastal erosion of Shungimbili Island. • Opportunity for revisions to the reserve boundaries in order to afford better protection for areas of high ecologically importance. Recommendations o SIMR is a key nursery for Elasmobranch species that are under threat both locally and worldwide. Blacktip sharks (Carcharhinus melanopterus) are present at high density in the sandy shallows surrounding the island. In addition, there have been unconfirmed sightings of lesser guitar fish (Rhinobatus annulatus) or sandshark juveniles. Blue spot stingrays (Dasyati kuhulii) are also abundant. Further studies
are recommended in order to determine the importance of the C. melanopterus nursery and estimate recruitment and survival levels. o Hawksbill and green turtles (Eretmochelys imbricata and Chelonia mydas) have been observed within SIMR and NIMR. At some sites in SIMR C. mydas have been observed frequently, with some very large individuals recorded as being near the maximum size for the species. Evidence from in-water observations, and information from other conservation organisations operating in the area, suggests that SIMR is a breeding and potential nesting site for C. mydas. Both species are listed on the IUCN red list (C. mydas as Endangered and E. imbricata as Critically Endangered). In order to establish whether the turtles breed at these sites, a survey of nesting signs, courtship and nesting behaviour is required, in addition to a population census. o All three reserve areas have extensive seagrass beds. The shallow beds at MBIMR exhibit particularly high biodiversity. These habitats are key nurseries and feeding grounds for many fish species. They are crucial for any recovery of the dugong (Dugong dugong) population, and are also of great importance to mollusc populations such as the edible sea cucumbers e.g. Holothuria edulis and tiger cowrie (Cypraea tigris). o MBIMR supports a small commercial operation, fishing for lobster (Palunirus spp). This, and other fishing activities, maintains a small camp of fishers at most times of the year. The commercial lobster diving operation operates using local labour and a compressor in situ. Further work is required to assess both the sustainability in terms of yield and renewal rates, and the economic and social impacts of this operation. o Observations made on catch levels at NIMR suggest that fishers harvest octopus at a very high rate, which is possibly above sustainable yield levels. In addition, many other mollusc species are harvested for both food and the curio trade. The octopus fishery is an important source of revenue for Mafia; however the high
Page 1: Frontier Tanzania Environmental Res
Page 4 and 5: Suggested Technical Report citation
Page 8 and 9: price it fetches may be contributin
Page 10 and 11: IV. RESULTS A. Nyororo Island Marin
Page 12 and 13: I. INTRODUCTION Project Aim To cond
Page 14 and 15: The reserves were established under
Page 16 and 17: III. METHODS A. Field Methods 1. Re
Page 18 and 19: Ground Proofing Methodology (Low Re
Page 20 and 21: Invertebrate Abundance Invertebrate
Page 22 and 23: Commercially Targeted Fish The meth
Page 24 and 25: Indian Ocean Bird wrasse Gomphosus
Page 26 and 27: Several areas of coral reef habitat
Page 28 and 29: area, the most extensive continuous
Page 30 and 31: Average abundance (+/- SE) 30 25 20
Page 32 and 33: Average abundance (+/- SE) 3 2.5 2
Page 34 and 35: stop off or shelter. Boats from the
Page 36 and 37: 2. Coral Reef Habitat a) Benthic Co
Page 42 and 43: 68% 5% 18% 2% 0% 1% 0% 6% 0% 0% Tha
Page 44 and 45: on Mbarakuni. At times of good weat
Page 46 and 47: edge is visible at around 10m deep.
Page 50 and 51: 97% 0% Figure 28. Average percentag
Page 52 and 53: c) Invertebrate abundance Invertebr
Page 54 and 55: lobster fishing. A foreign financed
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(Chaetodon trifascialus) are closel
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transects. Commercial fish species
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damage at present, but if further u
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VI. Appendices Appendix 1. Fish spe
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Whitespotted Epinephelus Grouper ca
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Biophysical Survey of Mafia Island Marine Reserves

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