Vessel noise and presence cause on-going impacts to SRKWs. Higher frequency underwater noise, typically from recreational and small commercial boats, masks SRKWs’ echolocation (how SRKWs find and capture their preferred food, Chinook salmon). Lower frequency underwater noise, typically from large commercial ships, interferes with SRKWs ability to communicate, causing SRKWs to expend more energy making louder calls and using higher frequencies on their calls. Even the presence of non-motorized boats causes SRKWs to change their behavior and expend more energy.
The 50 kHz frequency of the sonar in echo-sounders overlaps with the frequency of SRKW echolocation. Studies are underway to see if this impacts SRKWs.
Because SRKWs are not getting enough to eat due to the decline in Chinook salmon, any interference with their ability to find scarce prey and any unnecessary expenditures of energy further impacts the health of SRKWs and the growth of their population.
Oil Spill Risk:
SRKWs were listed as Endangered in 2005 in part because of concerns about potential oil spill impacts, particularly if the entire population is together in the vicinity of a spill.[i]
The 1988 Exxon Valdez oil spill in Prince William Sound Alaska caused an unprecedented high number of killer whale deaths in the two populations that were swimming through Prince William Sound at the time of the spill. The population of the AB pod is showing signs of a slow recovery; however, the transient AT1 population will likely become extinct.