Southern resident killer whale survival depends on reducing vessel activity

Scientists have said that if the vessel activity is reduced there is a greater chance that southern resident killer whale numbers could stop from dwindling and subsequently stabilize and even increase.

If the vessel activity is reduced, then the scientists hypothesize that the West Coast southern resident killer whales will spend more time hunting for Chinook salmon that will enable them to establish a constant food supply as well as increase their population.

The research, published in the journal Marine Pollution Bulletin, provides insights to guide conservation efforts and protect the estimated 73 remaining whales in the population. Research shows that these whales spend between 70 and 84 per cent of their time foraging in the absence of ships and boats to meet their daily energy needs.

Researchers studied the whales’ foraging behaviour in Haro Strait during a 2018 voluntary vessel slowdown, as part of a broader effort to reduce human-generated noise disturbance. The strait is a critical summer foraging habitat for the endangered whales.

The ECHO program was led by the Vancouver Fraser Port Authority and followed a successful earlier trial, which saw 55 per cent of vessels voluntarily reduce their speed to 11-knots when transiting through the strait, resulting in an overall noise reduction of 2.5 decibels.

Using a surveying instrument known as ‘theodolite tracking’ to determine the whales’ positions, researchers observed and categorized the group’s behaviour as either traveling, resting, socializing or foraging during each five-minute scan.

Researches also recorded the number, type and position of vessels in the area, then combined the data collected on vessels and whales with a sound propagation model, to predict the noise level of the ships and boats that whales were exposed to when they surfaced.

As noise levels increased, the whales were less likely to start foraging and more likely to stop the activity. The researchers suggest reducing vessel speed, lateral displacement within shipping lanes, replacing the noisiest ships in the fleet and rerouting shipping lanes are actions that industry can take to help these marine mammals.

Taking immediate action is more crucial than ever, following recent reports of three pregnant J pod whales now eating for two and will be raising their young in the years ahead.

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