Speaker
Description
Research using acoustic recordings to estimate animal population sizes is being applied increasingly frequently to both marine and terrestrial species. Here, data from the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) International Monitoring System (IMS) hydroacoustic stations have been used to monitor baleen whales. For example, several baleen whale species have been recorded at Diego Garcia in the Indian Ocean including blue (Balaenoptera musculus), fin (B. physalus) and suspected Omura’s whales (B. omurai). The CTBTO IMS has been collecting data at Diego Garcia across multiple decades and the placement of the hydrophones in the deep sound channel enables long-range detection of whale calls. By covering both large spatial and temporal scales, the CTBTO IMS is a valuable dataset for the potential assessment of trends in population size and distribution of several baleen whale species. To estimate whale population densities from CTBTO IMS instruments, simulation-based statistical methods have been implemented to estimate detection probability, a key parameter required for density estimation. The simulations require several data inputs including bearings to target whale calls, transmission loss data, noise level measurements and assumed source levels of the calls. Results from a case study focusing on Sri Lankan blue whale calls will be presented.
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