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Use of chemical profiles in assessing the feeding ecology of Alaska killer whales

Use of chemical profiles in assessing the feeding ecology of Alaska killer whales. Paul R. Wade | NOAA, National Marine Mammal Laboratory Craig O. Matkin, Lance Barrett-Lennard – North Gulf Oceanic Society Richard G. LeDuc - NOAA, Southwest Fisheries Science Center

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Use of chemical profiles in assessing the feeding ecology of Alaska killer whales

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  1. Use of chemical profiles in assessing the feeding ecology of Alaska killer whales Paul R. Wade | NOAA, National Marine Mammal Laboratory Craig O. Matkin, Lance Barrett-Lennard – North Gulf Oceanic Society Richard G. LeDuc - NOAA, Southwest Fisheries Science Center John W. Durban, Marilyn E. Dahlheim, Nancy Black – NOAA, National Marine Mammal Laboratory David P. Herman, Douglas G. Burrows, Margaret M. Krahn – NOAA, Northwest Fisheries Science Center

  2. 2005 summary: 14 Transient groups (19 biopsies) 22 Resident groups (15 biopsies)

  3. Use of chemical profiles in assessing the feeding ecology of eastern North Pacific killer whales Krahn et al. submitted, Marine Environmental Research

  4. Qualitative comparison of “indicator” fatty acids—fish and marine mammals Relative proportions in fish Proportions (wt%) in biopsy blubber compared to marine mammals for each killer whale ecotype Offshores Residents Transients Fish Marine mammals Fatty Acids SCMU C14:1n5 L H 1.4 3.5 4.2 C16:1n7 L H 19.6 21.4 27.1 Omega-3 C22:6n3 H L 0.92 0.93 0.57 On-going analyses of fatty acids of potential marine mammal prey

  5. Separation of killer whale ecotypes using DFA of Fatty Acids in blubber

  6. Separation of killer whale ecotypes using DFA of PCBs in blubber

  7. 1 Trophic Level offshore onshore Carbon and nitrogen stable isotope ratios of killer whales

  8. X Predicting the trophic level of killer whale prey Matkin & Saulitis diet: 50% gray whale 29% northern fur seal 14% minke whale 7% Steller sea lion NMML/NOAA diet: 18% gray whale 45% northern fur seal 9% minke whale 9% Steller sea lion 18% Dall’s porpoise

  9. Use of contaminant ratios to identify regional sources • California Signature: ∑DDTs/∑PCBs • high ∑DDTS reflects heavy use of DDTs in California before 1970s ban • Asian signature: ∑HCHs/∑PCBs & ∑chlordanes/∑PCBs • high ∑HCHs or ∑chlordanes from pesticides used long after the U.S. ban—ocean and air transport to Alaska • Asian signature of “new” DDT: p,p’-DDT/∑DDTs • high p,p’-DDT reflects recent pesticide use of DDTs in Asia or Central America (low = “old” source in California) • Alaska signature: low ∑DDTs/∑PCBs and high ∑chlordanes/∑PCBs • Presence of Asian signature and absence of California signature

  10. Ratio of DDT to PCB California signature

  11. Ratio of åchlordanes/åPCBs Asian signature

  12. “New” DDT (from Asia)High ratio = recent source

  13. Concentration of PBDEs (flame retardant) 12,600

  14. Ratio of PBDEs to PCBs California signature

  15. Conclusions • Offshore killer whales consume a diet that is clearly distinct from those of residents and transients • Offshore killer whales biopsied in Alaska feed at least part of the year in California, presumably on highly contaminated, high trophic level marine fish (not fur seals as earlier hypothesized) • Resident and transient killer whales in Alaska have contaminant ratios that appear to reflect the area where they are sampled in spring/summer (e.g., suggests they do not make large scale movements in fall/winter to other regions, unlike offshore whales)

  16. Conclusions • Resident killer whales in Alaska exhibit a gradient in chemical profiles from west (central Aleutians) to east (Gulf of Alaska) that likely represents a shift from off-shelf to continental shelf-based prey and lower to higher trophic level. • This supports the hypothesis that diets of EAI/R and GOA/R whales contain a high proportion of salmon, whereas the diet of the CAI/R whales may include lower trophic level, demersal prey. • Eastern Aleutian transients do not have a spring/summer diet that is composed exclusively of Steller sea lions, because stable isotope ratios show that their diet must include lower trophic level species to offset the high tropic level of the sea lions.

  17. Acknowledgments • Funding support • North Pacific Research Board • L. Jones of the NWFSC Marine Mammal Program • T. K. Rowles of the Marine Mammal Health and Stranding Response Program of NOAA Fisheries • Sample and data analysis • D. W. Brown, G. M. Ylitalo, C. A. Sloan, R. H. Boyer, R. W. Pearce and J. L. Bolton • Killer whale biopsy samples • R. L. Pitman and the Southwest Fisheries Science Center provided biopsy samples (Z38169, Z38170, Z38171 and Z38175) • Nancy Black of the Monterey Bay Whale Watch provided samples of the West Coast (California) killer whales • Killer whale prey data • G. M. Ylitalo, S. O’Neill, J. West and J. Buzitis for Chinook salmon • Kimberlee Beckmen for Steller sea lion

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