Two species of common dolphin play an important role in the Southern California Bight (SCB) ecosystem: Delphinus delphis, the short-beaked common dolphin, and D. capensis, the long-beaked common dolphin (Heyning and Perrin 1994). There are external differences between the two species in body length, beak length, coloration and shape of the melon. Furthermore genetic analyses (Rosel et al. 1994) have confirmed reproductive isolation between short-beaked and long-beaked common dolphins.
Long-beaked common dolphins have a muted criss-cross color pattern on their sides, a triangular or falcate (curved) dorsal fin, and congregate in large schools of hundreds of animals.
They are particularly susceptible to domoic acid poisoning. Domoic acid is a nerve toxin produced by harmful algal blooms (HABs). When HABs occur, sardines and anchovies eat the harmful algae. Marine mammals and birds that feed on sardines and anchovies then suffer the consequences of the accumulated toxin - illness and sometimes death. HABs have become more frequent over the past several years, perhaps triggered by climate change, urban runoff, and a host of other factors.
Why study them now? Together, these two species are the most abundant cetacean and the top cetacean predators in the SCB (Barlow et al. 2008). While responses to short- and long-term changes in climatic and oceanographic conditions can be expected, a large and growing coastal urban population in Southern California impacts the SCB and potential risks are emerging as threats to these populations. The risks include exposure to a wide range of anthropogenic impacts: commercial and recreational fisheries; habitat degradation due to pollution; effects of ship operations (e.g. noise and pollution) associated with two of the busiest commercial ports in the country (Los Angeles and Long Beach); and impacts associated with the U.S. Navy’s operations on the SCB test range. Evidence of exposure to some of these risks has been observed in specimens of stranded Delphinus species, especially D. capensis, which show vulnerability to domoic acid and effects of human interactions.
Scientific Name: Delphinus capensis
Diet: Sardines, hake, anchovies, sauries, small bonitos, other fish and squid
Avg lifespan in wild: 22 years
Size: Males: 6.6-7.7 ft (202-235 cm)
Females: 6.3-7.3 ft (193-224 cm)
(Heyning and Perrin, 1994)
Life History: We do not have sufficient life history data for long-beaked common dolphins, particularly from the Southern Califronia Bight
Threats: Tuna purse-seine fisheries; gill nets; domoic acid.
IUCN Status: Lower Risk/Least Concern