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Ecology, Social Structure and Contaminant Load Comparison of
Inshore/Offshore Bottlenose Dolphins in the Southern California Bight
Bottlenose dolphins are important bio-indicators of the health of marine ecosystems as they are predators at the top of the marine food chain. By studying these animals, we can learn more about the overall status of our oceans and assess the impact of human activities like overfishing and pollution. Careful monitoring is essential to the recognition of adverse trends in marine populations in a world that has neglected sustainability and pushed ocean “capacity” to the limit.
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Since 1996 the L.A. Dolphin Project has studied bottlenose dolphins inhabiting Los Angeles waters, focusing primarily on the inshore populations. We have found these animals to be present in the area year-round using the Santa Monica Bay mostly for foraging on bottom fish. Southern California appears to have two separate populations of bottlenose dolphins: coastal and offshore. Because of the logistical difficulties of following animals offshore, long-term studies have mostly looked at coastal dolphins found within 500 meters from shore. This project attempts to learn more about the offshore populations and compare that information to a continuing study of inshore groups.This study also allows us to continue our reseach work on the presence of skin diseases and physical deformities on both, coastal and offshore bottlenose dolphins, and compare our data with other researchers in California and along the Pacific coast.
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| Social interaction between coastal bottlenose dolphins |
Photo-identification and focal group behavioral descriptions form the key methods of answering questions about the social structure of these dolphin populations. Photo-identification of individuals is accomplished by taking clear photo records of all individuals’ dorsal fins found within a school for comparison, much like the use of a fingerprint. Photos and videos of individuals will also help to identify skin diseases and physical deformities on dolphins.
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LADP researcher photographing bottlenose dolphins
for photo-identification |
Behavior and association patterns are observed and comprehensive data recorded into a database that includes oceanographic conditions, satellite data, bioacoustic information and digital video providing us with a wide array of information that we may draw upon to enhance our understanding of these complex animals.
- Determine whether dolphins observed inshore (up to 0.5 km from shore) and offshore (from 0.5 km to 80 km from shore) belong to two separate populations
- Determine whether offshore dolphins are resident and if so to what area, by showing long-term site fidelity and regular resightings
- Compare contaminant levels between inshore and offshore populations of bottlenose dolphins to better understand pollution risks in these apex predators
- Identify skin diseases and physical deformities on coastal and offshore populations
- The data collected will also enable comparisons between the social structure of inshore bottlenose dolphins and those found offshore.
© 2005 Ocean Conservation Society.
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L.A. Dolphin Project 1
