Cetacean rapid assessment

Cetacean Rapid Assessment

Most research into wild marine mammals occurs in wealthy countries. Amazingly, we have still have very little idea what species are present, let alone the population size / health status / behaviour, etc. in many parts of the world. A solid first step to address this problem is to conduct a rapid assessment survey to determine which species of marine mammals are present in a given area.

The idea of a rapid assessment survey is fairly straightforward: you take a boat out and survey the entire coastline of a country using visual observers to record the number and species of any whales and dolphins encountered. As well as being large, surface present and often charismatic animals, and so possible to detect visually at relatively long ranges, dolphins and whales are also highly vocal, using sound to communicate and some species hunt/sense their surroundings with a sophisticated a bio-sonar. So, for most marine mammal surveys, it also makes sense to acoustically monitor the area we are visually surveying. We do this by towing a hydrophone (underwater microphone) array behind the survey boat. That way, if the sea is rough and the animals are difficult to spot, you can still detect the tell tale vocalizations of different species, and even localise their likely position.

A team led by Gill Braulik with Jamie Macaulay and Anja Wittich helping out conducted a rapid assessment survey of marine mammals in off the coast of Tanzania. We used a combined visual and acoustic survey method to determine the species of whales and dolphins present, and their spatial distributions along the coast of Tanzania. The survey was a success, and you can find our publication on this here (Braulik et al. 2018) and an infographic below.