The California blue doris (Felimare californiensis) is a dramatically colored nudibranch found of the coast of North America from Monterey Bay, California to Bahia de La Paz in Baja California Sur, Mexico. It apparently became extinct in the northern part of this range, and was completely gone from California by 1984. It began to reappear in a few isolated places in 2003. Apparently Santa Catalina Island is one of those isolated place, as this was where today’s photo was taken in 2015.
The reason for the local extinction in the northern part of the range is unknown, but it is speculated the disappearance along the mainland coast of southern California, but not at Santa Catalina Island could be due to industrial pollution reducing this nudibranch’s preferred prey, sponges in the genera Stelleta and Haliclona.
This photo was taken with a Canon EF100 mm f/2.8 macro lens on a Canon EOS 5D Mk. III in an Ikelite underwater housing. Lighting was provided by an Ikelite DS161 strobe set to eTTL exposure. The exposure was set to 1/60 sec at f/11 and ISO 200.