A REVIEW OF
pemba's Complex Reefs
The Case for Strengthening the Conservation of Pemba's Coral Reefs
Our research on Pemba Island’s coral reefs, led by Senior Scientist Mishal Gudka, was published online in July 2024 in the Journal of Regional Studies in Marine Science. The ten-year review of coral reefs in the Pemba Channel Conservation Area, a Marine Protected Area, identified significant ecological benefits that highlight the urgent need for investment in management and conservation. CORDIO Director Melita Samoilys, Senior Research Associate Kennedy Osuka and Coral Reef Scientist Swaleh Aboud are among co-authors. Read a summary of the study below.
Background
Coral reefs sustain the livelihoods of millions of people in the Western Indian Ocean (WIO), but these ecosystems face numerous threats, including marine heat waves causing coral bleaching, destructive fishing, and overexploitation. To protect these vital ecosystems, Marine Protected Areas (MPAs) have been established throughout the WIO. One such MPA, the Pemba Channel Conservation Area (PECCA), was established in 2005 along the west coast of Pemba Island, part of Tanzania’s Zanzibar Archipelago. PECCA aims to conserve biological diversity and cultural values while providing recreational, social, and economic benefits for present and future generations.
Pemba Island’s reefs account for 9% of Tanzania’s coral reefs and are renowned for their high coral and fish diversity, as well as their complex reef structures. There is a high dependency of communities on reef resources for food and income. However, despite their importance, there have been limited scientific studies of the health of these coral reefs.
The Study
The study took place along the coral reefs of the western side of Pemba Island, with four researchers collecting ecological data on benthic, coral, and fish communities in 2019 at 12 sites. Nine of these sites were previously surveyed in 2009 using similar methods.
Read a blog by the paper’s co-author, Randall Mabwa, about the 2019 surveys.
Click the PDF above to read the full paper
Key Findings
Despite their importance, the reefs off Pemba Island’s west coast were found to be in average condition in 2019. Average hard coral cover was 26%, with only two sites exceeding 40% and four sites below 15%. We recorded significant declines in the abundance of fish between 2009 and 2019, with 2019 fish biomass levels quite low, suggesting inadequate protection from fishing. The northern reefs were particularly degraded, dominated by rubble and lacking the complex structures needed by fish. In contrast, the southern reefs had healthier coral communities and fish populations, and high levels of coral recruitment, indicating the importance of intact reef structures for these ecosystems.
Recommendations
The study highlights the urgent need for improved investment in the management and conservation of PECCA to ensure the continued socio-economic and ecological benefits derived from the coral reefs. Despite the declining condition of Pemba’s reefs over the past decade, the high coral recruitment levels in the south offer potential for recovery. The severely degraded northern reefs will require significant interventions, for example, the control of destructive fishing practices such as ring-netting. In addition, Pemba Island’s unique features, such as its steep drop-offs, cold-water upwellings and gaps between reefs, may help them resist coral bleaching, and provide ideal habitats for endangered species such as groupers and sharks. This amplifies the impact that local actions including the establishment of no-take zones and stronger enforcement of regulations can have to maximize the health and benefits of these natural resources. Coral restoration can also be explored as a complementary management measure.