Underwater noise pollution

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Dolphins use sound to communicate and hunt. They use echoing techniques of  clicks  and whistles to located their prey. However, the frequency produced by construction boats and the construction itself fall within the range which dolphins use. The 650 ha. reclamation project will take several years and will gravely affect the health of dolphins and their ability to hunt in the long term.

The study provided by the EIA report only used the Ecological Acoustic Recorder (EAR) to measure and characterize vessel noise, which has its own limitation

  • The noise characteristics of HSFs at closer distance will provide critical information to understand the effect of the ferry noise as well as to determine the safe speed limit as a mitigation measure.
  • Apparently, there are other alternative methods to measure vessel noise at various distances from the noise source continuously, which should be adopted in this EIA study to gather information that is critical for evaluating the acoustic disturbance on CWD

The EIA report failed to meet the study brief requirement to study the anthropogenic noise generated by vessel traffic other than the HSFs without any justification

  • The study of other vessels should include all types of construction boats and transportation boats, and the negative impacts of a high volume of these boats in the works area (i.e. at least 300 boats in the works area during the peak of construction).
  • The EIA report cannot simply assume that these boats would not cause any impact on the dolphins without any substantiated study to back up such assumption.

The EIA report failed to meet the study brief requirement to study the acoustic behaviour of dolphins for detailed assessment of acoustic disturbance to CWD

  • Such assessment should be done in the presence and absence of noise generated from different types of vessels, including HSFs, construction boats, and transportation boats, as well as their cumulative impacts.
  • It is clear that the passive acoustic monitor (i.e. EAR) adopted in the present study is not the best method to study the acoustic behaviour of dolphins to satisfy the study brief requirement.