Recovery rates of bottlenose dolphin (Tursiops truncatus) carcasses estimated from stranding and survival rate data

Authors

James V. Carretta, NOAA Fisheries, Southwest Fisheries Science CenterFollow
Kerri Danil, NOAA Fisheries, Southwest Fisheries Science Center
Susan J. Chivers, NOAA Fisheries, Southwest Fisheries Science Center
David W. Weller, NOAA Fisheries, Southwest Fisheries Science Center
David S. Janiger, Los Angeles County Museum
Michelle Berman-Kowalewski, Department of Vertebrate Zoology, Santa Barbara Museum of Natural History, Santa Barbara, California
Keith M. Hernandez, Moss Landing Marine Laboratories, Vertebrate Ecology Lab, Moss Landing, California
James T. Harvey, Moss Landing Marine Laboratories, Vertebrate Ecology Lab, Moss Landing, California
Robin C. Dunkin, University of California, Santa Cruz, California
David R. Casper, University of California, Santa Cruz, California
Shelbi Stoudt, Marine Mammal Center, Fort Cronkhite, Sausalito, California
Maureen Flannery, California Academy of Sciences, Golden Gate Park, San Francisco, California
Kristin Wilkinson, Protected Resources Division, West Coast Region, National Marine Fisheries Service, NOAA, Seattle, Washington
Jessie Huggins, Cascadia Research Collective, Olympia, Washington
Dyanna M. Lambourn, Washington Department of Fish and Widlife

Date of this Version

2016

Citation

MARINE MAMMAL SCIENCE, 32(1): 349–362 (January 2016)

Comments

U.S. Government Work

Abstract

Recovery of cetacean carcasses provides data on levels of human-caused mortality, but represents only a minimum count of impacts. Counts of stranded carcasses are negatively biased by factors that include at-sea scavenging, sinking, drift away from land, stranding in locations where detection is unlikely, and natural removal from beaches due to wave and tidal action prior to detection. We estimate the fraction of carcasses recovered for a population of coastal bottlenose dolphins (Tursiops truncatus), using abundance and survival rate data to estimate annual deaths in the population. Observed stranding numbers are compared to expected deaths to estimate the fraction of carcasses recovered. For the California coastal population of bottlenose dolphins, we estimate the fraction of carcasses recovered to be 0.25 (95% CI = 0.20– 0.33). During a 12 yr period, 327 animals (95% CI = 253–413) were expected to have died and been available for recovery, but only 83 carcasses attributed to this population were documented. Given the coastal habits of California coastal bottlenose dolphins, it is likely that carcass recovery rates of this population greatly exceed recovery rates of more pelagic dolphin species in the region.