Chumbe Coral Reef: 55 Hectares, No Scuba, 474 Fish Species

What the sanctuary is, precisely

The Chumbe Reef Sanctuary is the fringing reef along the western shore of Chumbe Island, and its boundary is defined rather than approximate: all the water within 300 metres of the western high-water mark, between two stated points on the shoreline, marked on the water by four solar-lit demarcation buoys.

Its published area is 55.06 hectares — about 0.55 square kilometres — broken down by habitat into reef slope, intertidal pavement, seagrass, deep slope and deep water. The figure of roughly a third of a square kilometre that circulates is smaller than the managers’ own number. The closed forest reserve on the island is a further 16.64 hectares.

It is a total no-take zone, and it was the first declared marine protected area in Tanzania.

The legal record

The reef west of Chumbe was declared closed by the Department of Fisheries on 6 October 1992. A marine sanctuary agreement was signed on 3 January 1994, and the reef was declared the Chumbe Reef Sanctuary by legal notice 99 of 24 December 1994 under the Fisheries Act of 1988. The agreement has been renewed twice, in 2004 and 2014, and since 2014 the declaration has run under the Fisheries Act of 2010. The island itself is separately a gazetted historical site, added to Zanzibar’s antiquities register in 2002.

The rules are set by the non-profit company holding the management agreement, with a ministry and an advisory committee that includes government, community and university members — not by a national marine parks authority. That is the structural difference between Chumbe and Mafia, and it is why the answer to “what is allowed here” comes from the managers rather than from a statute.

What is in it

At least 90 per cent of East Africa’s hard coral species have been recorded here, and at least 59 coral genera are present in the sanctuary. No species count is published, only the genus figure and that proportion — any specific number of coral species quoted for Chumbe is not coming from its managers.

The fish list is 474 recorded reef fish species. The rounder figure of about 400 that circulates understates it. The commonly attached “fifty families” could not be verified.

Bleaching, measured

This is the part that makes Chumbe an argument rather than a description.

In the 1998 event, Chumbe lost approximately 30 per cent of its coral, predominantly Acropora, while the region as a whole lost between 70 and 99 per cent. Its managers attribute the difference to resilience built from the absence of other stressors.

In 2016, sea surface temperature ran above 30 degrees from late March into April and about 80 per cent of the sanctuary bleached, though not all of it fatally: by that September, live hard coral cover had fallen by 32 to 34 per cent overall, with close to 50 per cent mortality in the shallows. Recovery figures above 70 per cent also circulate for Chumbe; the managers’ own monitoring reports the loss as above, and the gap between “bleached” and “died” is where the confusion sits.

Reef health monitoring has run here every September to March since 2006, and the results are published.

Snorkelling it — and diving, which you cannot

Scuba diving is not permitted in the sanctuary, except for research, buoy maintenance and professional filming. This is a snorkelling site and only a snorkelling site. Guided snorkelling runs at a ratio of at least one ranger to every eight guests, after a compulsory briefing, under a code of conduct that covers touching and fin awareness.

Visits — day or overnight — must be arranged in advance. A boat offering to drop in at Chumbe as part of a sandbank circuit is offering something that does not happen. The snorkelling guide sets the reef against the rest of the coast, and conservation tours covers the governance model.

Common questions about the Chumbe reef