Dolphins of San Diego County David W. Weller, Ph.D. Marine Mammal & Turtle Division Southwest Fisheries Science Center National Marine Fisheries Science Center National Oceanic and Atmospheric Administration La Jolla, CA USA
Outline for Tonight Common Species Physical characteristics Ecology Distribution Group size Behavior Population size Curious facts
Small Boat Research Studies on Bottlenose and Risso s Dolphins off Southern California STUDY AREAS Coastal and Offshore San Diego County San Clemente and Catalina Islands Santa Cruz and Anacapa Islands FIELD METHODS Photo-Identification Biopsy Acoustics Telemetry Photogrammetry RESEARCH OBJECTIVES Abundance estimation Movement patterns Chemical and microbiological contaminant exposure Stress & reproductive hormone evaluation Evaluation of Navy sonar Population structure Health assessment Food habits SIGNIFICANCE OF WORK Monitoring of population status and trends Impacts of environmental perturbation, toxins and pathogens Relating dolphin health to human health Training, education, public outreach COLLABORATORS Scripps Institution of Oceanography Northwest Fisheries Science Center Southern California Coastal Water Research Project San Diego State University
NOAA Technical Memorandum NMFS JANUARY 2013 U.S. PACIFIC MARINE MAMMAL STOCK ASSESSMENTS: 2012 James V. Carretta, Erin Oleson, David W. Weller, Aimee R. Lang, Karin A. Forney, Jason Baker, Brad Hanson, Karen Martien, Marcia M. Muto, Mark S. Lowry, Jay Barlow, Deanna Lynch, Lilian Carswell, Robert L. Brownell Jr., David K. Mattila, and Marie C. Hill NOAA-TM-NMFS-SWFSC-504 U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Marine Fisheries Service Southwest Fisheries Science Center www.nmfs.noaa.gov/pr/
San Diego County Top Six Bottlenose Dolphin Coastal (Tursiops truncatus) Bottlenose Dolphin Offshore (Tursiops truncatus) Short-Beaked Common Dolphins (Delphinus delphis) Long-Beaked Common Dolphins (Delphinus capensis) Risso s Dolphins (Grampus griseus) White-sided Dolphins (Lagenorhyncus obliquidens)
Basic Anatomy Diagram from Dolphin Research Center
Risso s Dolphin: Grampus griseus 3.6 to 4 meters Large head and melon with crease Indistinctive beak Tall falcate dorsal fin (one of tallest relative to to body size) Heavily scarred Gray calves and adults white
Risso s Dolphin Distribution Map courtesy of the Convention on Migratory Species
Risso s Dolphin Worldwide distribution Temperate and tropical oceans CA/OR/WA pop. est: ~12,000 (2011 SAR) Prefer steep shelf-edge habitats 400-1000m deep Night/day feeding on squid Group size ~ 10-50 Often in widespread aggregations
Risso s Dolphin Slow moving Typically not interested in vessels Associates with bottlenose dolphins Harass gray whales Active at the surface
Risso s Dolphin: Take Home Scarred and light colored Tall dorsal Indistinct rostrum Common mistakes: Killer whales
Bottlenose dolphin: Tursiops truncatus 2.5 to 3.0 meters Falcate dorsal fin Short robust rostrum Gray color with lighter belly Bow-riders/surface active Two CA stocks: Coastal: ~400 animals Offshore: 1000+ animals (2011 SAR)
Bottlenose Dolphin Distribution Map courtesy of the Convention on Migratory Species
Bottlenose Dolphin Varied diet of fish/squid Small groups (~2-50) Coastal population Range N. CA to Baja Within 1km of shore Cautious yet curious Offshore population Readily associates with other species and boats
Bottlenose Dolphin: Take Home Gray color Distinct rostrum Common mistakes: None?
Pacific White-Sided dolphin: Lagenorhyncus obliquidens
Pacific White-Sided Dolphin Distribution Map courtesy of the Convention on Migratory Species
Pacific White-Sided Dolphin Medium sized ~ 2.1-2.2 meters Distinct hourglass pattern on flank and frosted dorsal fin Short rostrum/beak Large schools up to 3000+, but will break off in smaller groups (10-20) for feeding
Pacific White-Sided Dolphin Surface active/bow riders Rooster tail Readily associates with other species ~30,000 animals in WA/OR/CA waters (2011 SAR) Prefer colder waters Diet of lantern fishes, anchovies, hake and squid
Pacific White-Sided Dolphin: Take home Tri-colored No distinct rostrum Tall falcate dorsal fin (frosted) Common mistakes: Common dolphin
Common Dolphin Short-beaked: Delphinus delphis Long-beaked: Delphinus capensis High contrast coloring, hourglass marking Notable rostrum Long-beaked <2.2 meters Short-beaked <1.8-1.9 meters
Common Dolphin Distribution Map courtesy of the Convention on Migratory Species
Common Dolphin CA/OR/WA population estimate Short-beaked (Dd): 365,000 450,000 (2011 SAR) Long-beaked (Dc): 25,000 43,000 (2011 SAR)
Common Dolphin Diet varies with region Long-beaked (Dc): Coastal Short-beaked (Dd): Offshore Dive up to 200m Can school in the thousands Associate with other dolphins Bow-ride boats and off the pressure wave of large whales High bycatch numbers
Common Dolphin: Take Home Tri-colored Distinct rostrum Common mistakes: Pacific White-sided dolphin With each other
Less Common Dolphins off San Diego County
Killer Whale: Orcinus orca
Northern Right Whale Dolphin: Lissodelphis borealis
Short-finned Pilot Whales Globicephala macrorhynchus
False Killer Whale Pseudorca crassidens
Dall s porpoise: Phocoenoides dalli
Dolphin or Porpoise? Dolphin Family Delphinidae Wider range of body lengths, typically more slender bodies Hector s dolphin (1.7m) to Killer whale (~6m) Prominent rostrum Taller, falcate dorsal fin Conical teeth 25+ species Porpoise Family Phoceonidae Generally smaller, stout bodies ~2m or less Short, round rostrum Smaller, triangular dorsal fin with a rounded tip Fused neck vertebrae Flattened, spade shaped teeth 6 species