| Autor: |
MacGillivray AO; JASCO Applied Sciences, 4464 Markham Street, Victoria, British Columbia, V8Z 7X8, Canada., Li Z; JASCO Applied Sciences, 4464 Markham Street, Victoria, British Columbia, V8Z 7X8, Canada., Hannay DE; JASCO Applied Sciences, 4464 Markham Street, Victoria, British Columbia, V8Z 7X8, Canada., Trounce KB; Vancouver Fraser Port Authority, 100 The Pointe, 999 Canada Place, Vancouver, British Columbia, V6C 3T4, Canada., Robinson OM; Vancouver Fraser Port Authority, 100 The Pointe, 999 Canada Place, Vancouver, British Columbia, V6C 3T4, Canada. |
| Abstrakt: |
During 2017, the Vancouver Fraser Port Authority's Enhancing Cetacean Habitat and Observation program carried out a two-month voluntary vessel slowdown trial to determine whether slowing to 11 knots was an effective method for reducing underwater radiated vessel noise. The trial was carried out in Haro Strait, British Columbia, in critical habitat of endangered southern resident killer whales. During the trial, vessel noise measurements were collected next to shipping lanes on two hydrophones inside the Haro Strait slowdown zone, while a third hydrophone in Strait of Georgia measured vessels noise outside the slowdown zone. Vessel movements were tracked using the automated identification system (AIS), and vessel pilots logged slowdown participation information for each transit. An automated data processing system analyzed acoustical and AIS data from the three hydrophone stations to calculate radiated noise levels and monopole source levels (SLs) of passing vessels. Comparing measurements of vessels participating in the trial with measurements from control periods before and after the trial showed that slowing down was an effective method for reducing mean broadband SLs for five categories of piloted commercial vessels: containerships (11.5 dB), cruise vessels (10.5 dB), vehicle carriers (9.3 dB), tankers (6.1 dB), and bulkers (5.9 dB). |
