School of Natural and Environmental Sciences


Distribution and ecology of dolphins in Menai Bay Conservation Area, Zanzibar, Tanzania

Distribution and ecology of animal populations is dependent on a range of abiotic, biotic and anthropogenic factors. Understanding how these factors may affect animal distribution and behaviour is important for the understanding and conservation of species. This is particularly true for dolphin species in Zanzibar where dolphin tourism has replaced a previous hunt and become an important activity for the local socio-economy, particularly in the 270km2 Menai Bay Conservation Area (MBCA) off the south coast of Zanzibar, Tanzania.

There are small populations of 212 (CI 163-260) Indo-Pacific bottlenose dolphins (Tursiops aduncus) and 63 (CI 57-95) Indo-Pacific humpback dolphins (Sousa chinensis) resident in the MBCA. Previous research in the area have focussed on anthropogenic activities and their effect on these populations, including studies on effects of fisheries bycatch and tourism, while less effort has been given to the investigation of biotic and abiotic factors. This study aims to explore the effects of abiotic, biotic and anthropogenic factors on distribution and behaviour of dolphins in the MBCA, along with the creation of detailed bathymetric maps which will be invaluable for this and future studies.

The main research questions are:

(1) What habitat features can explain and predict dolphin distribution, and

(2) At what levels, if any, do human activities affect dolphin distribution.

These questions are addressed by conducting boat surveys along 90 transects covering the MBCA while employing a distance sampling approach. Data on dolphin occurrence and behaviour and human activities are collected visually while data on environmental parameters (depth, temperature, bottom topography and bottom type) are collected from a GPS plotter/echosounder. To compliment this remote sensing data (sea surface temperate, chlorophyll a) are sourced from MODIS satellite data, supplied by NEODASS (NERC Earth Observation Data Acquisition and Analysis Service). Finally dolphin temporal occurrence is recorded at three fixed locations within MCBA using cetacean click detectors (C-PODs).

All data are analysed in a GIS framework and the results will not only be new and interesting from an ecological research perspective, but also crucial in identifying key areas for management and conservation for these two vulnerable dolphin populations and other marine life in the MBCA.

Graduate student involved in the project: Andrew Temple (