A third blue whale has died in the Channel, in the past couple of weeks. All 3 were hit by ships; the third was alive when hit, and died instantly. They may have been injured, or incapacitated, before being struck; healthy whales can hear ships in time to move out of the way.
The Navy began testing new medium-frequency sonar at San Clemente, far to the south, just before the first whale was discovered. The second whale, showed no signs of physical damage to its ears. Of course, sound travels far under the ocean, and blue whales are profoundly sensitive to it.
A couple dozen blue whales have been feeding in the Channel lately, attracted by abundant krill. The Channel is part of the shortest route between Long Beach and Asia, and has a great deal of shipping traffic.