Design and operation specifications of an active monitoring system for detecting southern resident killer whales
Before final approval is given to the Snohomish County Public Utility District No. 1 for deploying the first tidal power devices in the United States in an open water environment, a system to manage the potential risk of injury to killer whales due to collision with moving turbine blades must be demonstrated. The Pacific Northwest National Laboratory (PNNL) is tasked with establishing the performance requirements for, constructing, and testing a prototype marine animal alert system for triggering temporary turbine shutdown when there is risk of collision with a killer whale. To develop a system that relies on active sonar two critical areas must be investigated - the target strength of killer whales and the frequency content of commercially available active sonar units. PNNL studied three target strength models: a simple model, the Fourier matching model, and the Kirchoff-ray mode model. Using target strength measurements of bottlenose dolphins obtained by previous researchers and assuming killer whales share similar morphology and structure, PNNL extrapolated the target strength of an adult killer whale 7.5 m in length at a frequency of 67 kHz. To study the frequency content of a commercially available sonar unit, direct measurements of the signal transmitted by the sonar were obtained by using a hydrophone connected to a data acquisition system in both laboratory and field conditions. The measurements revealed that in addition to the primary frequency of 200 kHz, there is a secondary frequency component at 90 kHz, which is within the hearing range of killer whales. The amplitude of the 90-kHz frequency component is above the hearing threshold of killer whales but below the threshold for potential injuries.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1034981
- Report Number(s):
- PNNL-SA-81594; PP0814000; TRN: US201204%%273
- Resource Relation:
- Conference: OCEANS 2011, September 19-22, 2011, Kona, Hawaii
- Country of Publication:
- United States
- Language:
- English
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