SAN FRANCISCO — Federal officials are promoting a campaign to get ships to slow down as they approach San Francisco and other California ports so they are less likely to injure or kill whales.

The San Francisco Chronicle reported Friday marine experts say four of the 10 gray whales found dead near San Francisco this year were killed by ships.

Greater Farallones National Marine Sanctuary superintendent Maria Brown says that when the campaign started in 2013 only 17% of incoming ships were slowing down. Now 45% are throttling down by half, to 10 knots.

There are no speed limits at sea, so vessels can zip along as fast as they want, usually 20 knots, or about 23 mph.

The large vessels often travel through national marine sanctuaries to get to their destination ports.

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Information from: San Francisco Chronicle, http://www.sfgate.com

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