The relative occurrence of the 16 most common cetacean species in the Southern California Bight (SCB) was compared from the 1950s through 2012 by examining at-sea sighting and stranding data. While systematic survey and population abundance/density data have been available since the 1970s, prior data were collected opportunistically. Comparisons were made through a literature review and using recent results from 15 aerial surveys conducted in the SCB from 2008 through 2012. We attempted to address inconsistency in type of effort across studies by ranking the relative sighting frequency of the most common species based on the most representative study for each period. This comparison revealed changes in the relative occurrence of some species across the approximately 60-y reviewed period. Since the 1950s, common dolphins have remained the most common “species” of cetacean in the SCB. Risso’s dolphin and fin, blue, humpback, and Bryde’s whales appear to have increased in relative occurrence. The relative occurrence of the common bottlenose and northern right whale dolphins; Dall’s porpoise; and gray, killer, minke, Cuvier’s beaked, and sperm whales do not appear to have changed notably since the 1950s. There is possible indication of recent decreased relative occurrence of the Pacific white-sided dolphin. The short-finned pilot whale has decreased since the 1950s and has not been recorded in the SCB since the 1990s, concurrent with the observed relative increase in Risso’s dolphins. Overall, recent aerial surveys indicate that the 16 most commonly seen species in the SCB, in descending order of frequency, were common dolphins (two species), Risso’s dolphin, fin whale, common bottlenose dolphin, gray whale, blue whale, Pacific white-sided dolphin, humpback whale, northern right whale dolphin, common minke whale, Dall’s porpoise, killer whale, Bryde’s whale, Cuvier’s beaked whale (the latter three tied in ranking), and sperm whale. Given that the reviewed historical data from the 1950s and 1960s are virtually the only sources of information available to examine trends over the last 50 to 60 y in this area, we believe this comparative ranking approach provides useful information not available from other sources.

Small aircraft enable a “bird’s eye” view of marine mammal behavior at/near the water surface. During 2008-2013, we flew 87,734 km of line transect and “focal follow” aerial survey effort in the Southern California Bight to systematically collect data on 2,707 sightings of ~222,457 individual cetaceans representing 19 species, funded by the U.S. Navy Pacific Fleet. Focal follows involved circling a cetacean group for 5-60+ minutes and taking high-definition (HD) video and photos to document behavior primarily of blue, fin, gray, humpback, sperm, minke and killer whales; and Risso’s, common bottlenose, short-beaked and long-beaked common, and northern right whale dolphins. HD media allow photoidentification of individuals and species confirmation from altitudes of 1,000-1,500 feet. The “bird’s eye” 71 perspective facilitates descriptive and quantitative analyses of behavior previously little described for typically offshore species: whale calf nursing/back-riding, group cohesion, social affinity/composition, group shape and dimension “envelope”, cues leading to group behavior changes, mixed species interactions, individual whale respiration/dive rates, etc. Behavior differs significantly by species, calf presence, time of day, time of year, subregion, water depth, slope, distance from shore, and presence of other species. For example, Risso’s dolphins were 13 times more likely to rest than common dolphins, and dolphin group size increased significantly with calf presence. As species body size decreases, group size increases and individuals decrease distance between neighbors. We hypothesize that inter-specific differences of spacing and behavior are related to predation pressure, food resources, and communication capabilities/needs that lead to occupation of different niches within the same ecosystem.