Drowned Out: How Marine Vessel Noise Impacts the Southern Resident Killer Whale Population in the Salish Sea
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The endangered Southern Resident killer whale (SRKW) population that consists of a total of 73 members, concentrates in the Salish Sea off the coast of British Columbia, Canada and Washington, USA during the summer. The Salish Sea is also an area of high human occupancy and activity, resulting in high amounts of marine vessel traffic. The noise created by vessel traffic can negatively affect SRKW life processes, which threatens the small population’s survival. The purpose of this paper is to determine how marine vessel noise affects the SRKW population as well as how commercial and whale watching vessels specifically affect SRKW, as they are notable industries in the area. Another objective is to assess how affective current SRKW-specific legislation is. An examination of published journal articles, theses, and other literature reveals that vessel noise originates from multiple characteristics of a vessel such as length, size, propeller cavitation, distance, and speed. Whale watching vessel noise is mainly due to certain practices such as leapfrogging which increases noise levels near pods, masking SRKW communication. Additionally, commercial shipping vessels increase background noise, masking SRKW calls, and interfering with echolocation. Vessel noise affects SRKW social behaviour including the reduction of SRKW communication space, vessel noise masking SRKW calls, SRKW decreased detection of calls, altering calls, and increased surface active behaviours. Vessel noise disrupts SRKW echolocation and navigation of prey, reduces the amount of resting and foraging time, causes avoidance behaviour, and decreases energy production. SRKW can also suffer from hearing loss due to the constant exposure of vessel noise. This constant exposure to vessel noise can also lead SRKW to permanently abandon their habitat. Current Canadian and American SRKW legislation such as the Oceans Protection Plan and the Species at Risk Act establish protection zones, fines for violating SRKW critical habitat zones, and voluntary vessel slowdowns but overall, legislation isn’t properly addressing noise level effects on SRKW. Further, noise levels in critical habitat zones have been found to significantly affect SRKW communication. Findings have shown that voluntary regulations and boundaries established aren’t effective and enforcement of regulations is minimal. Recommendations include developing SRKW education campaigns as well as creating clear channels of communication among researchers, policy-makers and the public to increase awareness of current legislation. Additionally, creating one universal piece of SRKW legislation for easier management of vessels and SRKW, altering shipping routes in the summer to avoid critical habitats, and making all voluntary measures for vessel slowdowns obligatory could aid in the survival of the SRKW population in the Salish Sea.