If you listen to reports about ships colliding with migrating whales off the coast, navigators would well be warned to be on the alert.  The bulk of the 20,000 behemoths will be swimming by this month. These warnings were stirred when a fin whale’s carcass washed ashore a few weeks ago in Point Loma, believed to have been the victim of a ship encounter. Meanwhile, smaller boats with curious sightseers will be on the waters off our coast getting a close-up view as these spectacular animals head for warm Mexican breeding lagoons. The whales will have completed a 12,000-mile journey from the Bering Sea — an annual odyssey that began in October. As to collisions, some say these are common occurrences off Southern California shores. Collisions are likely noted here more often because of reports by the Navy. Coast Guard officials recently proposed altering shipping lanes for the ports of Los Angeles and Long Beach, in part to avoid prime whale habitat around the Channel Islands National Marine Sanctuary. Officials from the Southwest Fisheries Science Center in La Jolla say the whales end up right in the middle of the shipping lane. Researchers said the casualty count might be only 10 percent of the actual total because some whales sink quickly and others float out to sea undetected.  Often longer than a bus and weighing 30 to 40 tons, gray whales move in large pods. The gray whale consumes bottom-dwelling crustaceans and krill by turning on its side and scooping up huge amounts of sediment from the sea floor.  According to the Birch Aquarium in La Jolla, gray whales are most frequently seen off San Diego from late December through March. Grays are relatively slow swimmers, cruising at an average speed of three to five miles per hour.     • How time flies — Boxing champion Muhammad Ali celebrated his 70th birthday last month. I remember covering two of his West Coast fights as a boxing writer. We were ringside at what was then called the San Diego Sports Arena in 1973 when ex-Camp Pendleton Marine Ken Norton upset the “Great One”  via split decision.  He broke Ali’s jaw in the process. Later, Norton went on to hold the world heavyweight title for a couple of months.  • Just in case — San Diego’s Coast Guard says it’s ready, should a cruise ship get into trouble off our coast. Hopefully, the Coast Guard is not having to prepare for a ship tragedy like the one off the west coast of Italy at Giglio Island. However, in November 2010 it helped take care of a problem when the cruise ship Splendor was crippled by a disabling fire south of San Diego. Since then, the Coast Guard said it has learned from the rescue experience. “Once a year, we meet with everybody, exercise it and then we debrief what worked, what didn’t work, how can we do this better?” said Coast Guard Lt. Sean Groark. Rescuers say they have a plan and they practice for emergencies, but maintain that the ocean is dynamic and can be unpredictable. — Johnny McDonald is a longtime writer and columnist for the San Diego Community Newspaper Group. He can be reached at [email protected].