The Mafia Island, Tanzania, Whale Shark Project

Project Overview.

Mafia Island Whale Sharks.

Mafia Island is a hub for ecological studies on whale sharks. Our research covers various aspects of their lives, including their movements, feeding ecology, genetics, population trends, behavior, social grouping, health, and the human threats they face.

1. Fine-scale Movements and Habitat Use

We employ passive acoustic telemetry to track the whale sharks' movements and map their activity hotspots and seasonal changes. This information is used to lobby for protection measures, such as a go-slow zone for boats.

2. Short- and Long-term Feeding Ecology

Our research involves collecting plankton samples from feeding events and conducting biochemical analyses to study their long-term feeding ecology. We use stable isotope and fatty acid analyses to examine the sharks' position in the food web, feeding locations, and prey sources.

3. Genetic Connectivity

We collect tissue samples for genetic analysis to examine the connectivity between individuals at Mafia Island and around the world. Our kinship analysis helps identify close relatives among the whale sharks.

4. Population Trend Analyses

Our team analyzes population size trends over the last 8 years and applies robust models to assess whether the population is recovering or if stricter protection is needed.

5. Improving Demographic Parameter Estimates

We aim to estimate essential demographic parameters, such as survival and growth rates. To achieve this, we utilize stereo-videography to accurately measure the sharks over time.

6. Behavioural Studies

Our behavioral studies involve the use of behavioral tags to measure the sharks' 3D position and acceleration, which allows us to identify their behaviors even when not directly observed, such as at night.

7. Social Grouping

We assess whether the same individual sharks are preferentially seen together and use the acoustic telemetry dataset to study longer-term social groupings. This information helps us evaluate potential disturbances from human activities, such as tourism.

8. Health Assessment

To understand the whale sharks' biology and bioenergetics, we analyze their comparative growth rates using stereo-videography. In the future, monitoring individual shark health over time may become possible through blood sample collection.

9. Human Threats

We track scars and injuries using photographs to assess the main threats faced by the whale sharks in each location, such as boat strikes or entanglement in nets. By monitoring injury frequency over time, we can evaluate the effectiveness of management strategies and regulations.