Chelonia Limited

  Cetacean Monitoring Systems


Environmental impact assessments

PODs have been used successfully in Environmental Impact Assessments.

Pioneering work has been done by the National Environment Research Institute (NERI) in Denmark on the impact on cetaceans of the construction of a wind farm at Horn’s Reef off the Danish coast.

The study design adopted was BACI (Before/After comparison between Control and Impact sites). T-POD data showed significant behavioural effects during pile driving that disappeared within 4 to 5 hours of the end of this very noisy activity.

The constructors took measures to reduce exposure of individual porpoises to very loud sounds by using aversive pingers beforehand and ramp-up procedures at the start of pile driving. The rapid return to normal behaviour among the porpoises suggests that these measures were successful. Work continues to assess long term effects which could quite possibly be beneficial to porpoises, but are not known at present.

The initial study of wind farm construction on Horns Reef was exceptionally challenging and used the earliest versions of the T-POD in very difficult conditions for mooring equipment. Despite these issues, significant results were obtained. This project is described in the following report:

Carstensen, J., Henriksen, O.D. & Teilmann, J. (2006). Impacts of offshore wind farm construction on harbour porpoises: acoustic monitoring of echo-location activity using porpoise detectors (T-PODs). Marine Ecology Progress Series 321: 295-308.

Other reports about this project are available on the NERI web site at:

Culik and Koschinski deployed T-PODs in a study using simulated wind farm noise and showed, not only avoidance of the sound source judged by visual tracking, but also an increased rate of detection of porpoise sonar at the sound source, demonstrating a mixture of avoidance and investigation by the animals. This was the first demonstration of such a response. This project is described in the following report:

Sven Koschinski, Boris M. Culik, Oluf Damsgaard Henriksen, Nick Tregenza, Graeme Ellis, Christoph Jansen, Günter Kathe (2003). Behavioural reactions of free-ranging porpoises and seals to the noise of a simulated 2 MW windpower generator. Marine Ecology Progress Series Vol. 265: 263–273.

Prospective BACI

If PODs are deployed two or more years prior to the commencement of a project the data collection will allow a much more powerful method for assessing the impact. This can help to avoid incorrectly attributing natural, but infrequent, changes in patterns of cetacean habitat use, to effects caused by construction or other sources of disturbance.