Mnemba Atoll: The Island You Cannot Visit and the Reef You Can

Two things the name gets wrong

Mnemba lies about three kilometres off the north-eastern corner of Unguja, a short boat run from the shore at Matemwe. It is roughly ten hectares of sand and vegetation inside an oval fringing reef of about seven kilometres by four.

It is therefore not an atoll. An atoll is a ring of reef encircling a lagoon; this is an island with a reef around it, and the accurate phrase is Mnemba Island and its reef. Zanzibar’s own marine conservation literature uses “Mnemba Atoll” freely, so the usage is established — but the geography behind it is not.

And you cannot go to it. The island is held on a long private lease and non-guests are not permitted to land. An excursion sold as “Mnemba Island” is a trip to the water around it, which is worth knowing at the point of booking rather than from the boat.

The restricted zone, and the figure to stop repeating

There is an exclusion zone, and it is usually quoted as a flat five hundred metres. The primary document says otherwise. A Marine Special Area around the island, announced in late 2023 by Zanzibar’s Ministry of Blue Economy and Fisheries together with the Mnemba Island Marine Conservation Area, sets a restricted zone extending between 400 and 700 metres from the island — not a uniform radius. The same measure caps access at eight boats a day, each carrying up to seven visitors and two crew, within set hours and with no anchoring.

The wider conservation area around it was gazetted in 2002, covers about 337 square kilometres from the north of the island down the east coast to Chwaka Bay, and is an IUCN Category VI multiple-use area managed by Zanzibar’s Department of Marine Conservation with village committees in around thirty-one villages.

What the reef is actually like

Better on fish than on coral, and busier than any photograph suggests.

Zanzibar’s marine conservation guide records one of the highest levels of species diversity of any reef in northern Unguja here, including 36 hard coral genera, and puts the fish list at more than 200 species — against roughly 600 in some reference works. Spinner, spotted and bottlenose dolphins occur, white-tip reef sharks are regular, and green turtles nest on the island’s beaches. A no-fishing zone on the house reef to the north-west has seen significant recovery.

Against that: live coral cover on the reef east of the island was put at 12 per cent in a 2021 regional assessment, with high fish abundance over it. The same assessment lists congestion of fishers and tourists, and consequent reef damage, first among the area’s threats. Reporting in 2024 described a coral decline of around 90 per cent over two decades and up to 200 tour boats a day; that is journalism rather than survey data, and is attributed here rather than asserted. A restoration project with a coral nursery has run on the house reef since 2021, with artificial structures placed outside the restricted zone to draw dive-boat pressure away.

Going early or in the shoulder weeks are real answers to the crowding, and so is an access-controlled site such as Chumbe. Snorkelling and diving cover it against the rest of the coast.

The fee question

The 2023 measure provides for a conservation fee levied by the conservation area itself, which is more than existed before. What still cannot be found in any independent source is an account of what that revenue pays for or who audits it. If a Mnemba trip is sold as supporting conservation, those remain the questions worth asking, and the conservation tours guide explains why.

Common questions about Mnemba