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Changes in northern Tanzania coral reefs during a period of increased fisheries management and climatic disturbance
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2009 (English)In: Aquatic conservation, ISSN 1052-7613, E-ISSN 1099-0755, Vol. 19, no 7, 758-771 p.Article in journal (Refereed) Published
Abstract [en]

1. Surveys of coral reefs in northern Tanzania were conducted in 2004/5 with the aim of comparing them over an∼8-year period during a time of increased efforts at fisheries management and the 1998 El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) coral mortality event that caused 45% mortality in northern Tanzania and much of the Indian Ocean.

2. Changes associated with both management, its absence, and the ENSO were found but changes were generally small and ecological measures indicated stability or improvements over this period, particularly when compared with reports from much of the northern Indian Ocean.

3. Fisheries management in two areas increased the biomass of fish and benthic communities. A small fisheries closure (0.3 km2) displayed little change in the coral community but ecological conditions declined as measured by sea urchins and fish abundances. This change may be associated with its small size because similar changes were not measured in the large closure (28 km2).

4. The few sites without any increased management were still degraded and one site had experienced a population explosion of a pest sea urchin, Echinometra mathaei.

5. The lack of significant changes across this disturbance indicates that these reefs are moderately resilient to climate change and, therefore, a high priority for future conservation actions.

Place, publisher, year, edition, pages
2009. Vol. 19, no 7, 758-771 p.
Keyword [en]
1998 ENSO, climate change, coral bleaching, fisheries closures, Indian Ocean, marine protected areas
National Category
Zoology Ecology
Research subject
Animal Ecology
URN: urn:nbn:se:su:diva-25798DOI: 10.1002/aqc.1020ISI: 000271778200004OAI: diva2:200534
Available from: 2009-03-05 Created: 2009-02-25 Last updated: 2011-09-13Bibliographically approved
In thesis
1. Habitat structure, degradation and management effects on coral reef fish communities
Open this publication in new window or tab >>Habitat structure, degradation and management effects on coral reef fish communities
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Coral reefs are among the most diverse and productive ecosystems on earth, and are critical to the survival of tropical marine ecosystems and sustenance of local human populations. However, coral reefs are quite vulnerable to disturbances, both natural and anthropogenic. This thesis looks at how coral reef communities have responded to climactic disturbances, particularly the 1997-98 El Niño Southern Oscillation (ENSO) and subsequent coral bleaching and mortality that affected much of the Indian Ocean, including the coastal waters of Tanzania, where the study was conducted. In particular, it investigates the effects of coral bleaching, habitat degradation and reef spatial arrangement on reef fish assemblages.

Habitat structural complexity and spatial arrangement of reefs had an effect on reef fish communities. Fish communities showed patterns in distribution among habitats and between patch and continuous reefs. Fishes preferred live to bleached/dead or eroded coral, but trophic groups reacted differently to patch and continuous reefs. There were slight changes in fish abundance and significant changes in fish diversity on experimental, bleached branching Acropora coral plots over a period of one year. While fish abundance on one site increased shortly after a bleaching event, 6 years later fish abundance had decreased significantly. Conversely, coral reef communities in northern Tanzania had changed little over an 8-year period, with minor changes associated with the 1997-98 ENSO and the presence or absence of fisheries management. The coral reefs in the region were found to show high variability in community structure and responses of associated fish and invertebrate communities.

The findings of this thesis indicate the importance of habitat structure and spatial arrangement of reefs, the detrimental effects of coral bleaching, and the possibility that some reefs and some (generalist) reef fish taxa may exhibit resilience to climate change.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2011. 46 p.
fish assemblages, climate change, coral degradation, Indian Ocean, patch reefs, coral bleaching, resilience
National Category
Ecology Zoology
Research subject
Animal Ecology
urn:nbn:se:su:diva-62187 (URN)978-91-7447-360-5 (ISBN)
Public defence
2011-10-07, Ahlmannsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript. Available from: 2011-09-15 Created: 2011-09-12 Last updated: 2011-09-13Bibliographically approved

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Yahya, Saleh A.S.
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