Cetacean Ecology for Santa Monica Bay and Nearby Areas, California in the Context of the Newly Established MPAs

Data on cetacean ecology are important for monitoring animals and developing conservation and management strategies in a specific area, and are crucial in the decision making process during the creation of marine protected areas (MPAs). Cetacean occurrence, distribution and behavior were investigated in Santa Monica Bay, California (1997-2007). A total of 425 boat-based surveys documented three species inhabiting the bay year-round - the common bottlenose dolphin, Tursiops truncatus, the long-beaked common dolphin, Delphinus capensis, and the short-beaked common dolphin, D. delphis - and ten species occurring occasionally. Coastal bottlenose dolphins were mostly found traveling, diving and feeding in waters within 0.5km of shore in 81.4% of the sightings (n=221), but were also observed occasionally in offshore waters. All other species were seen \u3e0.5km of shore, often feeding near escarpments and submarine canyons. Endangered species such as blue whales (Balaenoptera musculus), humpback whales (Megaptera novaeangliae) and northern right whale dolphins (Lissodelphis borealis) were also recorded in the bay. The presence of a rich and diverse cetacean fauna suggests the need for long-term monitoring and a precautionary approach toward these species. These data are also essential in conservation and management decisions associated with the current creation of a MPA in Santa Monica Bay

Aspects of the ecology and behaviour of bottlenose dolphins (Tursiops truncatus) in Santa Monica Bay, California

The occurrence, distribution, site fidelity, group size and behaviour of common bottlenose dolphins (Tursiops truncatus) were assessed during a photo-identification study conducted between 1997-2001 in Santa Monica Bay, California. Bottlenose dolphins occurred yearround in the bay and were encountered on 56.8% of all surveys (n, total surveys=211). This species was found in waters within 0.5km of shore in 80.0% of the sightings (n=157), but sometimes found in deeper waters further offshore (>0.5km). No correlations between anomalies in sea surface temperatures during the 1997-98 El Niño event and sighting frequencies were observed. Group sizes varied significantly between schools observed inshore and offshore in the bay, with the largest groups sighted offshore. A total of 290 dolphins were individually photo-identified based on long-term natural marks on their dorsal fins. Forty-four individuals (15.2%) were encountered in both inshore and offshore waters, showing no exclusive fidelity to inshore waters. The low resighting rates of known individuals provided little evidence of long-term year-round site fidelity for Santa Monica Bay, revealing a range greater than the chosen study area. Several individuals, however, were resighted over one or two year periods, generally during more than one season. This suggested that these dolphins were highly mobile within the inshore waters of the Southern California Bight but they also spent time foraging and feeding in Santa Monica Bay, probably due to the presence of submarine canyons within this area. The behavioural budget for this species showed a predominance of activities characterised by travel and dive-travel (69.0%) and feeding (5.0%), indicating a fairly high proportion of time devoted to searching for prey and feeding in the study area

Habitat Partitioning by Three Species of Dolphins in Santa Monica Bay, California

Despite scientific advances and increases in public interest in whales and dolphins, much information is still lacking to properly understand these animals living in an environment often threatened by human activities. Previously not investigated, the Santa Monica Bay is a heavily impacted area occupied year-round by various marine mammals, including threatened species. The purpose of this proposal is to provide a means to fill the need for critical information in the area.This study takes a “precautionary approach” which may identify potential problems thereby preventing the disappearance of this and other species from the Bay. Project methodology involves weekly field surveys from a powerboat using laptop data collection, photo- and video-recording, plankton net tows, GIS, remote biopsy sampling, and a recently developed “computer-assisted system” for use in identifying dolphins.By building upon research begun in 1996, this project will provide an important framework on the composition, distribution, and abundance of cetacean species. This will also illustrate the likely indirect changes in marine mammal populations during the 1997-98 El Niño event and the subsequent La Niña. This framework represents a valuable opportunity to investigate how significant these events are on cetacean populations and their prey, and how populations may shift in relation to changes in oceanographic conditions.A second phase of this project will look at bottlenose dolphin behavior and habitat use with relation to human activities in the nearshore habitats of the Bay and collect data on pollutant levels in the animals. Dolphins are apex predators in a coastal ecosystem sensitive to fluctuations of temperature, with corresponding changes in the populations of zooplankton and fish. Gathering data on dolphins, known as bio-indicators of the status of the environment, and monitoring trends in their populations, is an excellent way of protecting all marine organisms living in the local ecosystem

Aspects of the ecology and behaviour of bottlenose dolphins (Tursiops truncatus) in Santa Monica Bay, California

The occurrence, distribution, site fidelity, group size and behaviour of common bottlenose dolphins (Tursiops truncatus) were assessed during a photo-identification study conducted between 1997-2001 in Santa Monica Bay, California. Bottlenose dolphins occurred yearround in the bay and were encountered on 56.8% of all surveys (n, total surveys=211). This species was found in waters within 0.5km of shore in 80.0% of the sightings (n=157), but sometimes found in deeper waters further offshore (>0.5km). No correlations between anomalies in sea surface temperatures during the 1997-98 El Niño event and sighting frequencies were observed. Group sizes varied significantly between schools observed inshore and offshore in the bay, with the largest groups sighted offshore. A total of 290 dolphins were individually photo-identified based on long-term natural marks on their dorsal fins. Forty-four individuals (15.2%) were encountered in both inshore and offshore waters, showing no exclusive fidelity to inshore waters. The low resighting rates of known individuals provided little evidence of long-term year-round site fidelity for Santa Monica Bay, revealing a range greater than the chosen study area. Several individuals, however, were resighted over one or two year periods, generally during more than one season. This suggested that these dolphins were highly mobile within the inshore waters of the Southern California Bight but they also spent time foraging and feeding in Santa Monica Bay, probably due to the presence of submarine canyons within this area. The behavioural budget for this species showed a predominance of activities characterised by travel and dive-travel (69.0%) and feeding (5.0%), indicating a fairly high proportion of time devoted to searching for prey and feeding in the study area

Habitat Partitioning by Three Species of Dolphins in Santa Monica Bay, California

Despite scientific advances and increases in public interest in whales and dolphins, much information is still lacking to properly understand these animals living in an environment often threatened by human activities. Previously not investigated, the Santa Monica Bay is a heavily impacted area occupied year-round by various marine mammals, including threatened species. The purpose of this proposal is to provide a means to fill the need for critical information in the area.This study takes a “precautionary approach” which may identify potential problems thereby preventing the disappearance of this and other species from the Bay. Project methodology involves weekly field surveys from a powerboat using laptop data collection, photo- and video-recording, plankton net tows, GIS, remote biopsy sampling, and a recently developed “computer-assisted system” for use in identifying dolphins.By building upon research begun in 1996, this project will provide an important framework on the composition, distribution, and abundance of cetacean species. This will also illustrate the likely indirect changes in marine mammal populations during the 1997-98 El Niño event and the subsequent La Niña. This framework represents a valuable opportunity to investigate how significant these events are on cetacean populations and their prey, and how populations may shift in relation to changes in oceanographic conditions.A second phase of this project will look at bottlenose dolphin behavior and habitat use with relation to human activities in the nearshore habitats of the Bay and collect data on pollutant levels in the animals. Dolphins are apex predators in a coastal ecosystem sensitive to fluctuations of temperature, with corresponding changes in the populations of zooplankton and fish. Gathering data on dolphins, known as bio-indicators of the status of the environment, and monitoring trends in their populations, is an excellent way of protecting all marine organisms living in the local ecosystem

California Sea Lions Use Dolphins to Locate Food

Aggregations by 3 species of dolphins (the bottlenose dolphin [Tursiops truncatus], the short-beaked common dolphin [Delphinus delphis], and the long-beaked common dolphin [Delphinus capensis]) and California sea lions (Zalophus californianus) were investigated in Santa Monica Bay, California. Groups were followed and observed during 201 boat-based surveys conducted in 1997–2001 documenting that sea lions were aggregated in 18.6% of the sightings with bottlenose dolphins (150 bottlenose dolphin sightings) and in 45.9% of the sightings with 1 of the 2 species of common dolphins (98 common dolphin sightings). Aggregations of bottlenose dolphins and sea lions were observed in inshore (,500 m from shore) and offshore (.500 m) waters, whereas common dolphins and sea lions were observed only in offshore waters. These aggregations were often recorded feeding near escarpments and submarine canyons, showing a striking preference for these bathymetric features. The results show that sea lions spend a significant amount of time following dolphins, sea lions initiate aggregation and departure from dolphin schools, these aggregations occur more often than is expected by chance, and no aggressive behavior between sea lions and dolphins was ever observed at or near the surface. I argue that sea lions may take advantage of the superior food-locating abilities of dolphins. This paper provides the 1st detailed description of mixed-species aggregations and habitat usage by 3 dolphin species and sea lions

Dolphin sympatric ecology

Interspecific associations between two or more species of the family Delphinidae have been reported by many scientists, but the sympatric ecology of such dolphin associations has not been studied in great detail. A few field investigations have been conducted on this subject in different parts of the world on species such as bottlenose dolphins (Tursiops spp.), short-beaked common dolphins (Delphinus delphis ), and killer whales Orcinus orca ). Sympatric dolphins seem to use different strategies to co-exist when resources appear to be limited, including dietary divergence (different prey preference, slightly diverse diet,different feeding time) and/or different habitat use shallow versus deep waters, flat areas versus submarine canyons and escarpments, different travel routes). This paper presents a review of some well-studied dolphin species found in sympatry and discusses the nature of habitat and resource partitioning as well as studies on aggressive behaviour displayed by species living in the same habitat

Habitat Partitioning by Three Species of Dolphins in Santa Monica Bay, California

Volume: 104Start Page: 113End Page: 12