Tiger Shark
MONITORING
This long-term monitoring project using photo-ID is a non invasive method to characerize and track the population structure of tiger sharks around Fuvahmulah.
First started in 2016 by our colleagues from Fuvahmulah Dive School, Pelagic Divers Fuvahmulah joined in a collaborative effort in 2022. Up to date we have identified over 300 individuals, with a highly female dominated bias (85%).
Photo-ID
Photo-ID gives us more than names and faces. It lets us quantify residency, return rates, sex ratios, size classes, and population structure by matching images across years and seasons. These individual re-sightings are the backbone for studies of movement and behaviour at the local scale
There are several ways to identify individual tiger sharks, including their countershading patterns, stripe shapes, and fin structures. Additional features such as scars, unusual pigmentation, old injuries, or missing fin tips can also help distinguish one shark from another.
In Fuvahmulah, we primarily use countershading for identification, specifically the grey-to-white transition line just in front of the pectoral fin. This pattern is unique to each tiger shark and differs from left to right, much like a human fingerprint, making every individual easily recognisable.
Some sharks can also be identified by more distinct features, such as embedded hooks, damaged jaws, or notched and cut dorsal fins.
Alongside identifying individual sharks during our dives, we also document key details about their aggregation patterns and behaviour. Each day, we maintain a dive log that records the time, duration, and depth of every dive, as well as environmental and human-related factors that may influence tiger shark behaviour.
We monitor variables such as the number of divers and boats present, tides, currents, and wind conditions. Thanks to the support of several dive centres, we also compile an annual encounter list of identified individuals, helping us understand seasonal patterns and when higher numbers of sharks are present around the island.
