Abstract
Offshore windfarms provide renewable energy, but activities during the construction phase can affect marine mammals. To understand how the construction of an offshore windfarm in the Maryland Wind Energy Area (WEA) off Maryland, USA, might impact harbour porpoises (Phocoena phocoena), it is essential to determine their poorly understood year-round distribution. Although habitat-based models can help predict the occurrence of species in areas with limited or no sampling, they require validation to determine the accuracy of the predictions. Incorporating more than 18 months of harbour porpoise detection data from passive acoustic monitoring, generalized auto-regressive moving average and generalized additive models were used to investigate harbour porpoise occurrence within and around the Maryland WEA in relation to temporal and environmental variables. Acoustic detection metrics were compared to habitat-based density estimates derived from aerial and boat-based sightings to validate the model predictions. Harbour porpoises occurred significantly more frequently during January to May, and foraged significantly more often in the evenings to early mornings at sites within and outside the Maryland WEA. Harbour porpoise occurrence peaked at sea surface temperatures of 5°C and chlorophyll a concentrations of 4.5 to 7.4 mg m-3. The acoustic detections were significantly correlated with the predicted densities, except at the most inshore site. This study provides insight into previously unknown fine-scale spatial and temporal patterns in distribution of harbour porpoises offshore of Maryland. The results can be used to help inform future monitoring and mitigate the impacts of windfarm construction and other human activities.
Highlights
With the development of offshore energy infrastructure and increases in ship traffic, the world’s oceans are becoming busier and noisier [1, 2]
Passive acoustic monitoring of marine mammals in the area began in November 2014 to obtain baseline data prior to windfarm construction
Harbour porpoises were detected during the greatest proportion of days at the most inshore site, site 1, but were detected for the most hours at the farther offshore site, site 3 (Table 1)
Summary
With the development of offshore energy infrastructure and increases in ship traffic, the world’s oceans are becoming busier and noisier [1, 2]. Noisier oceans are a concern for marine mammals as they use sound for communication, foraging, and navigation [3, 4]. HB was the recipient of all funding. These funding agencies were given the opportunity to review the study design, preliminary results, and manuscript. The funding agencies did not participate in the analyses or manuscript preparation
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