[CINC] CINMS onGray Migrations-2012

[paul jr petrich]

Hi All,
 This is an excerpt from our CINMS summarizing official NOAA data about the most recent research on Gray Whale migrations. The link I passed on to Cubby in my previous email last night has the whole article. The 2008 American Cetacean Society Conference focused on Gray Whale research, and hit upon all the calving and feeding issues discussed by Hal, Marty, and Cubby, except the new reevaluations about routes through our Channel Islands. If you want specific references to abstracts about those studies, let me know ( from 2008 ). Cubby says he emailed Peter about the specific studies pertaining to the local routes .  Keep on Swimin, Paul


Whales arrive at Santa Barbara Island from a variety of directions and pass along either (western/eastern) shore. From Santa Barbara Island, most head for Santa Catalina Island and pass along the seaward shore. 

Once past the southern Channel Islands (Santa Catalina and San Clemente), most whales return to the coast. Some whales continue on into the Sea of Cortes, but most spend their winters in and near lagoons on the west coast of Baja California and the mainland coast of Mexico near Yavaros. 

It has long been believed that most gray whale offspring (calves) are born in Mexican waters in and near the lagoons. But more recent studies have revealed that a higher than expected number of calves are actually born during the southern migration, as far north as southern Oregon. Some mothers and calves have been spotted passing south through the Channel Island sanctuary waters. 

Gray whales begin leaving the lagoons for the northward migration as early as mid-January; so the beginning of the northbound migration overlaps slightly with the end of the southbound migration near Baja California and Southern California in January and February. The northward migration is shorter than the southward migration, and it occurs in two distinct waves or 'pulses'. The earlier pulse includes a larger cross section of the whale population. The later, smaller pulse consists primarily of females and their calves. 

The occasional observation of females and calves or yearlings in the same kelp areas off the Channel Islands on successive days has led to speculation that quiet kelp beds are of special importance to newborn and juvenile whales during spring. Given that 60% of the kelp beds in theSCB (the Southern California Bight--which extends from Point Conception to Cabo Colnette, Baja California) are in CINMS waters, some young whales might be expected to linger there. One reason the northbound migration takes longer is probably due to whales stopping to feed on kelp, which is more bountiful in the spring. 

As with the fall/winter migration, during the spring/summer migration some gray whales do not complete the migration to subarctic or arctic waters, electing instead to spend summer and/or fall in the waters of California, Washington, British Columbia, or Alaska. The number of animals in these "summering" populations appears to be increasing, along with the growth of the population at large (around 25,000 gray whales in the North Pacific as of 1996).

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