We began our morning trip with great looks at our feathered and flippered friends just behind our slip in Quivira Basin at the baitfish floating dock. California sea lions were resting from their feeding forays, and the gulls, cormorants, pelicans, egrets and herons were hoping for an opportunistic chance to grab a few live anchovies when the fishing boats were collecting buckets of the live fish. We passed through the Mission Bay Channel entrance and went southwest over the deep Coronado Escarpment, an underwater feature that rises north of the Coronado Islands, located about 20-miles south in northern Baja California, Mexico. We did not see much for seabirds and cetaceans until we changed course toward the northwest. 5-miles off of Point LaJolla, we encountered an uncommon cetacean in these parts, the Risso’s Dolphin, about 20 of them exhibiting a sleeping behavior. These molluscivores are interested in cephalopods or squid, which are soft-bodied animals or molluscs. Because squid come up to the surface at night, these dolphins are nocturnal. Hence, they are often found exhibiting a behavior known as semi-hemispherical sleeping, in which they turn one-half of their brain off and essentially take “cat-naps”. Risso’s are covered in scars from the sharp tooth-like projections found on the feeding tentacles of squid. The ones we witnessed were older, meaning they had more scars on their bodies from the daily battles to obtain their preferred squid meals. Calamari anyone? What was curious is that we also saw about the same amount of the Offshore Bottlenose dolphins milling about and interacting occasionally with the Risso’s.
On our afternoon trip, we were greeted with a rare sighting of late, that of the sun burning off the marine layer. Our guests felt the suns rays and had smiles on their faces. It was amazing that we had 4 different species of dolphin family members seen during our 3-hour tour. The first pod was a megapod of the Short-beaked common dolphins that were exhibiting some really cool behaviors. Very high, arched porpoising, breaches, tail slaps and synchronized swimming and attempted matings and cool courtship displays. We counted around 600 dolphins. Then, a bit further to the north, we saw the mixed species pod of Risso’s and Bottlenose dolphins. On our way back, we saw a half-dozen Long-beaked Common dolphins. This incredible diversity is an example of the Eastern Tropical Pacific being a guild for many different species of marine mammals that seem to have little competition with each other as they can exploit different prey items in the same general area of the ocean. Some dolphins frequent the epi-pelagic (surface waters where air and water meet) and others the mesopelagic realm, the latter is known as the “twilight” zone where the ocean is deeper & darker with minimal sunlight. Many animals in this deeper realm exhibit bioluminescence or “life light”. We tried our best to find the big, baleen whales, but it’s likely the krill and forage fish are still low in numbers/density. Our blue whale season is in swing, so give it a try to see the largest mammal on the planet on a future San Diego Whale Watch. -naturalist Greg