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Kakulu Sagiatok, Cape Dorset

Trophic Links – Forage Fishes, Their Prey, and Ice Seals in the Northeastern Chukchi Sea. Part II – Ice Seals. CMI Review – December 10, 2009 S. Carroll L. Dehn B. Norcross B. Holladay. Kakulu Sagiatok, Cape Dorset. The Players – Pagophilic Seals. Photo: NOAA. Photo: NOAA.

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Kakulu Sagiatok, Cape Dorset

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  1. Trophic Links – Forage Fishes, Their Prey, and Ice Seals in the Northeastern Chukchi Sea Part II – Ice Seals CMI Review – December 10, 2009 S. Carroll L. Dehn B. Norcross B. Holladay Kakulu Sagiatok, Cape Dorset

  2. The Players – Pagophilic Seals Photo: NOAA Photo: NOAA • Bearded Seal (Erignathus barbatus) • 2-2.5m length, ~450-500lbs • Prefer transition zone with medium ice-cover • Ringed Seal (Phoca hispida) • 1-1.5m length, ~100-150lbs • Prefer land-fast ice ? Photo: NOAA Photo: NOAA • Spotted Seal (Phoca largha) • 1.3-1.7m length, ~180-250lbs • Prefer ice-edge • Ribbon Seal (Phoca fasciata) • 1.3-1.7m length, ~180-250lbs • Prefer ice front

  3. Background – Key Issues • Sentinel species: long-lived, high trophic level marine predators • Important link to higher trophics • Loss of sea-ice as a platform • Sea-ice related changes in food web assemblages and productivity • Industrial development in ice seal habitat • Subsistence importance

  4. It’s all about Food • It takes food to grow and reproduce! Dietary shift is often the first sign of change, followed by:  Stress  Body Condition  Resistance to Disease  Reproductive Output  Mortality  Population declines • Understanding MM response and adaptive potential is critical

  5. Sedna’s Realm Objectives -Determine trophic level of ice seals -Determine ice seal trophic history -Compare trophic levels of forage fishes to those of ice seals -Develop isotopic mixing models Kakulu Sagiatok, Cape Dorset

  6. Sample Collections • Samples of ringed, bearded, spotted, and ribbon seals collected during Native subsistence harvests • In collaboration with: • Alaska Department of Fish & Game • North Slope Borough, Department of Wildlife Management • Targeted specimens: • Liver - short term dietary record • Muscle – longer term dietary record • Claws – dietary history • Stomach contents – dietary snapshot

  7. Collections • *Spotted seal harvest for 2009 not yet inventoried by ADF&G • Challenges in obtaining all tissues for the same individuals • Continue sampling in 2010 to increase sample size, in particular for claws

  8. Sample Preparation • Archived seal samples have been sub-sampled and freeze-dried • Homogenization and isotope analysis is in progress • Some archived samples were requested through the Museum of the North • Total body homogenates of Arctic cod, Bering flounder, and Arctic staghorn sculpin are presently examined for the effect of lipid removal on stable isotopes • Method development for seal claws complete and preparation of “new” samples in progress Photo: S. Carroll

  9. Stable Isotope Primer • d15N used to identify trophic level and predator-prey relationships • ↑ in consumer as trophic level ↑ • d13C used to identify feeding location and feeding habitat • No ↑ with trophic level, but carbon source indicator

  10. Carbon Isotopes in Bowhead Baleen Schell et al., 1989 • Carbon from surrounding area is incorporated in baleen as it grows • Baleen oscillations can be measured ~18 years 1 minimum (Beaufort) + 1maximum (Bering/Chukchi) =1year

  11. Isotopic Record in Seal Whiskers Cherel et al., 2009 • Male Antarctic fur seals • Whiskers show records of annual migrations • AA polar front vs. subtropical front • Associated with switch in prey • AA krill vs. mesopelagic fishes

  12. Ringed Seal Migrations Olokhaktomiut and Paulatuk Hunters and Trappers Committee, EMC, and DFO • All seals tagged in 2001/2002 in Canada moved westward • Age range from pup to 4-year • Undertake sporadic migrations between Beaufort and Chukchi/Bering seas http://www.beaufortseals.com/telemetry.htm

  13. Ringed Seal Migrations – Carbon Isotopes Dehn et al., 2007 Muscle Tissue • Beaufort Sea depleted in 13C compared to Bering/Chukchi seas • Can migrations be detected using claws?

  14. Claws – Growth Layers Photo: S. Carroll • Front flipper claws grow continuously • Keratin layers are deposited annually • Light growth: Summer / Fall • Dark growth: Winter / Spring • Distal wear after ~10 years • Carbon and nitrogen isotopes are incorporated into growing claws, representing diet at time of growth • Trophic history! • Can elucidate seasonal importance of prey and annual shifts

  15. Claws – How to… Trimmed of tissue and fur Cleaned of dirt, blood, and grime in ultrasonic water bath Cleaned of lipids using chloroform/methanol Photo: S. Carroll Light and dark bands identified Drilled each layer with Dremel tool Powder of each layer analyzed separately for 15N and 13C Photo: S. Carroll

  16. Trophic History from Claws – Ringed Seal Keratin enriched in 15N over prey by ~2.5‰ in 13C by ~3‰ RS-5-18-00 Female 5 years Harvested in Barrow N: 10.4 ± 1.2 C: -24.9 ± 0.7 N: 15.5 ± 1.0 C: -20.9 ± 0.4 TL

  17. Trophic History from Claws – Ringed Seal RS-2-00 Male 7 years Harvested in Barrow • 95-96 feeding on high TL • 97-98 feeding low TL

  18. Trophic History from Claws – Ringed Seal • 95-96 feeding on high TL • 97-98 feeding low TL • 00 feeding high TL RS-1-01 Female 21 years Harvested in Barrow

  19. Anything Unusual during these Years? 1997-98 1995-96 http://ingrid.ldeo.columbia.edu/%28/home/alexeyk/mydata/TSsvd.in%29readfile/.SST/.PDO/ Warm Cool

  20. What could it Mean? • Cold pool over shelf prohibitive to some fish species in “warm years” • Warm corridors form in “cold years”, providing abundant fish forage for seals

  21. Photo: NOAA

  22. Trophic History from Claws – Bearded Seal • 95-96 feeding on high TL • 97-98 feeding low TL • 00 feeding high TL BS-7-02 Female 28 years Harvested in Barrow

  23. Trophic History from Claws – Bearded Seal BS-1-01 Male 32 years Harvested in Barrow • Seasonal differences in TL • Migration

  24. Trophic History from Claws – Bearded Seal BS-6-02 Female 32 years Harvested in Barrow • Seasonal differences in TL • Migration

  25. Sea Ice Differences? Richter-Menge et al., 2008 • 95-96 and 00 – low ice years • 97-98 – high ice year • Possible impacts on benthic food chain

  26. Juveniles • 15N in utero likely resembles values of mother with no enrichment • Resources of mother and fetus at equilibrium during early term • As fetal demand increases, maternal proteins from tissue breakdown rather than diet? • Enrichment? • High trophic level in juveniles • Incorporate isotopic signature of mother from milk • Increased protein turnover and growth

  27. Summary • Claws capture trophic history of ice seals! • No seasonal migratory pattern (based on 13C) in ringed and bearded seals • Sporadic excursions • Little evidence of regular seasonal prey switching in ringed seals • But possibly related to PDO • Seasonal differences between high and low trophic level foraging in bearded seals • Possibly related to sea ice • Prefer high ice coverage • YOY seals show enriched 15N signature • In utero • Lactation / Weaning

  28. Thank You! Subsistence Hunters in Coastal Alaska Lori Quakenbush Taqulik Hepa Jill-Marie Seymour Greta Krafsur Anna Bryan Mark Nelson Christy Gleason

  29. Questions ? http://www.arved-fuchs.de/husavik/seals/Seals/geninformation.html

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