Silurian Surveys

The HWDT research vessel Silurian is the perfect platform from which to study Hebridean cetaceans. For the last three years HWDT have been undertaking dedicated boat based surveys through out the south-west Hebrides, the survey area is defined below.

In the past this area has been little studied and virtually no dedicated survey work has been undertaken. The aim therefore over two years is to conduct broad baseline surveys throughout the entire area. This will allow us build up a picture of the diversity, range and distribution of species found in Argyll waters. This information can then be used to establish relative abundance of species throughout Argyll waters. From this initial three year database, we can start to build up a picture of what areas are important for individual species and identify ‘hotspots’ of activity. These ‘hotspot’ areas will then be studied in more depth in the future. A report summarising 2003/2004 data can be found here.

The surveys are undertaken every month from April to October and are 7 days in length. In addition to HWDTs core crew of researchers we are assisted by volunteers. If you are interested in helping in this work then please click here to volunteer. During the 7 days course, we collect as much information as we can about the animals we see, the environment they live in, the way in which they behave and external factors such as shipping, acoustic noise etc. This is done using a number of different research techniques explained below.

     Visual Surveys

During all surveys HWDT observers are out on deck watching and scanning for cetacean activity. If the weather is calm enough we also place an observer up in the crows nest half way up the mast . The visual surveys are based on line transect methods (the standard survey method used for studying cetaceans) and strict protocols are followed to ensure that data is as accurate as possible.

Photo identification studies

    Oceanographic studies

The distribution of cetaceans is thought to be heavily influenced by the oceanographic features and variables that exist through and across the water column. During our surveys HWDT collects as much oceanographic data as possible. This includes logging constant depth readings throughout our surveys and also acquiring salinity and temperature profiles down through the water column and periodic intervals. Readings from the water column are taken by deploying an oceanographic instrument called a CTD (which measures Conductivity, Temperature and Depth). The model HWDT uses is called a Seabird 19 and is deployed from the back of the vessel . This data is then downloaded and saved on to the ship board computer.

Acoustic surveys