School of Natural and Environmental Sciences

Projects

Acoustic monitoring of the temporal and spatial occurrence of cetaceans off Blyth, Northumberland

EDF Graphic
Figure 1: Map showing the deployment locations for seven C-PODs to monitor the temporal and spatial occurrence of harbour porpoise (Phocoena phocoena)

This project use Cetacean Click Detectors (C-PODs) to determine the temporal and spatial occurrence of harbour porpoises (Phocoena phocoena), dolphins (white-beaked dolphin (Lagenorhynchus albirostris) and common bottlenose dolphin (Tursiops truncatus)) in the offshore windfarm development site off Blyth, Northumberland between June and August 2015. Seven C-Pods have been deployed (see Fig. 1); three C-PODs in the development area by the NOAH/Array site and two C-PODs at a north and south control site, respectively.

Marine mammals use sound for navigation, prey detection and communication. Increased levels of anthropogenic generated noise from shipping, marine construction, seismic surveys and offshore renewable energy installations may impact marine mammal distribution, foraging and reproductive success and hence affect their conservation status. To date marine noise impact on marine mammals has focused on impact from the construction and operation of marine wind farms and use of bycatch mitigation strategies.

Passive Acoustic Monitoring (PAM) can be used as both an aid and replacement for traditional visual based survey methods in odontocete studies worldwide. Where cetacean activity is not well understood, PAM has an advantage over traditional boat based surveys in that PAM captures presence of marine mammals which may not be visible at the surface and may be missed by vessel surveys. In addition the amount of survey effort to carry out 24/7 monitoring by vessel is cost prohibitive. PAM exploits the high-frequency broadband click vocalisations produced by odontocetes (tooth whales) for navigation and foraging purposes, inferring presence and absence over time. It allows for fine-scale study of occurrence of odontocetes (toothed whales such as dolphins and porpoises) by recording high-frequency broadband click vocalisations across large temporal scales, through full diel cycles, due to their low power consumption and long battery life. Acoustic detection effectiveness is not significantly affected by time of day, weather, visibility, dolphin surface presence, sea state, observer bias or other factors which hamper traditional visual boat surveys. Further, acoustic monitoring has been shown to yield up to seven times the detection rate of visual surveys.

Accurately assessing the occurrence of cetacean populations along the UK northeast coast is difficult due to a scarcity of year-round spatial and temporal data. Previous assessments have primarily relied on sightings data collected during limited dedicated surveys, seabird surveys, surveys from ships of opportunity and by shore based volunteers. As a result survey effort has varied and the quality of the resulting data and the methods used is difficult to attain. Visual surveys are affected by weather with the most useful data collected at sea states 0-2, so data is often concentrated in the summer months. Acoustic survey techniques can provide data on cetacean occurrence in all conditions; however these methods have not typically been applied along this coast.

The aim of this project is to address the lack of detailed and unbiased data to allow comprehensive assessment of the temporal and spatial occurrence of the harbour porpoise and white-beaked dolphin in the Blyth windfarm development site and adjacent waters a survey using autonomous PAM Cetacean Click Detectors (C-PODs).