1 / 37

On their own: migrations of northern fur seal pups from increasing and decreasing populations

On their own: migrations of northern fur seal pups from increasing and decreasing populations . Mary-Anne Lea, Tom Gelatt, Devin Johnson, Jeremy Sterling, Rolf Ream, Sharon Melin and Rod Towell. National Marine Mammal Laboratory, NOAA Fisheries, Seattle . Northern fur seal breeding sites.

duena
Download Presentation

On their own: migrations of northern fur seal pups from increasing and decreasing populations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. On their own: migrations of northern fur seal pups from increasing and decreasing populations Mary-Anne Lea, Tom Gelatt, Devin Johnson, Jeremy Sterling, Rolf Ream, Sharon Melin and Rod Towell National Marine Mammal Laboratory, NOAA Fisheries, Seattle

  2. Northern fur seal breeding sites 56% of population & decreasing Small increasing populations

  3. NFS pup production – Pribilof Islands North Pacific Regime shifts Post-exploitation Commercial harvest Sustainable harvest 2006 St. Paul : 109,937, = 10.5% less than 2004 St. George: 17,070 = 1.2% greater than 2004

  4. Northern fur seal life history • - Alternates between terrestrial and aquatic environment • - Congregate on islands during the breeding season ~ 4 mo. Then migratory – in the North Pacific Ocean ~ 8 mo. • Pribilof population has continued to decline for unknown reasons and is now at the 1917 population level when it was increasing at approximately 8% annually following the termination of pelagic sealing. • Bogoslof population has increased at 12%/yr since 1997

  5. Why study pup dispersal? • Northern fur seal breeding populations currently exhibit markedly different population trajectories • consequently post-weaning dispersal and migratory behavior may vary between populations and age classes • mortality of juvenile animals is high and environmental conditions encountered during the first year likely influence survival

  6. Study objectives 1. Record the winter movements of newly weaned NFS pups from increasing and decreasing populations in Alaska and California 2. Document the diving behavior of a subset of these pups to examine relationships between diving, age and oceanographic features 3. Assess the degree of overlap in foraging habitat use between breeding sites and age classes 4. Determine environmental factors influencing the spatial and temporal distributions of migration and foraging within and between years.

  7. Tag deployment – Oct/November 2005

  8. SPLASH Location & dive data n=40 Tag deployment – November 2005 n=99 Kiwisat 101 Location data n=59

  9. Timing of pup departures St Paul Is. – 10 Nov (28 Oct – 18 Nov 2005, n=44) St George Is. – 9 Nov (7-14 Nov 2005, n=20) Bogoslof Is. – 9 Nov (29 Oct – 26 Nov 2005, n=20) California San Miguel Is. –26 Nov (13 Nov- 3 Dec 2005, n=15) Alaska

  10. Aleutian Pass usage – St Paul Is pups 20% used Amukta Pass Median was 7.5d

  11. Aleutian Pass usage – St George Is pups 24% usead Seguam Pass Median was 9.6d St George Island (n=17)

  12. Aleutian Pass usage – Bogoslof Is pups 33% used Samalga Pass Median was 2.9 days (n=17)

  13. Median transit time to Aleutian passes St Paul Is. – 11.0d (n=31) – max d in Bering Sea: 79.1d St George Is. – 10.3d (n=18) – max d in Bering Sea: 35.1d Bogoslof Is. – 6.1d (n=17) – max d N of Aleutians: 220.1d Male-female transit times St Paul M: 21.0d F: 13.5d St George M: 17.0d F: 9.2d P<0.05 Bogoslof* M: 16.7d F: 9.0d *220d max transit removed

  14. Synchrony of mother-pup departuresconcurrent NPRB/NMML work provided opportunity to compare • mean interval between the departures of 17 mother-pup pairs was 5.8 ± 2.4d • 59% of pups departed earlier than mothers • in three cases mother and pups departed on the same day

  15. Mother-pup departures: same day 13 hrs apart 61098 Bogoslof mother pup

  16. Mother-pup departures: same day Mother and pup Traversed same region 12 h apart Bogoslof Is. pup female Environmental conditions on the day of departure may influence travel direction

  17. Distribution of 97 northern fur seal pups (Nov 2005 – Aug 2006) St George Is.

  18. Distribution of 97 northern fur seal pups (Nov 2005 – Aug 2006) St Paul Is.

  19. Distribution of 97 northern fur seal pups (Nov 2005 – Aug 2006) Bogoslof Is.

  20. Distribution of 97 northern fur seal pups (Nov 2005 – Aug 2006) Transition region San Miguel Is.

  21. Distribution in relation to age class and sex Russia Alaska Canada USA

  22. Modeled hourly instantaneous speed ms-1 215 days

  23. Summary • little to no synchrony in departures between mother and pups independent dispersal patterns • high degree of overlap in dispersal patterns of Alaskan pups from St Paul, St George and Bogoslof • pups exhibit large scale migrations from Russia to California – pups ranging farther west than adult females • current results are preliminary and future analysis will incorporate 67 pups from 2006/7 • 35/67 still transmitting as of 22 January: • St. George: 9/18 • St. Paul: 19/25 • Bogoslof: 7/15 • San Miguel: 0/9

  24. Inter-annual comparison NFS pup distribution (Oct-Dec)

  25. Acknowledgements • Alaska Fisheries Science Center • National Marine Mammal Lab • National Academies of Science NRC Research Associateship Program • Rolf Ream, Alain Springer, Sara Iverson and Alison Banks for the kind use of their NPRB-funded female tracking data. • St George and St Paul Island communities for helpful support • Jason Baker, Kate Call Tony Orr, and Jim Thomason, Mike Williams and Tonya Zeppelin for help in the field • Research was conducted under the marine mammal Permit No. 782-1708 issued to the NMML.

  26. Time spent plot for 97 pups – Nov-Aug 2006 Latitude Time spent per 25 x 25km grid cell 0.1 % 0.2 % 0.3 % 0.4 % Longitude >0.5 %

  27. Distribution of 97 northern fur seal pups (Nov 2005 – Aug 2006) Transition region San Miguel Is.

  28. Warm core eddy feature and adult female tracks Clockwise Positive SSH

  29. Tracks of 17 mother-pup pairs ! Female tracks Pup tracks (n=17)

  30. Study objectives • The migratory movements and winter destinations of northern fur seals (NFS) in their first year at sea; • The foraging activity of this age class as inferred from diving data, when available, or with less certainty, from the amount of time spent in an area; and • Determine environmental factors influencing the spatial and temporal distributions of migration and foraging within and between years. Additional secondary aims include: 1. examining island effects on migration parameters; 2. determining the effects of sex on migration parameters; and 3. the ontogeny of dive behaviour throughout the winter for pups instrumented with satellite relayed dive loggers (SDRs).

  31. Northern fur seal Bogoslof Island pup production 2005 12,631 (SE = 335) +12% per year since 1997

  32. Female movements 2005/6 & surface Chl-a conc. 0 mg/m3 1 2 3 4

  33. Aleutian Pass usage – St Paul Is pups Amukta - 7.5d Amukta Pass (20%) (n=31)

  34. Aleutian Pass usage – St George Is pups Seguam Pass St George Island (n=17) 1 2 Seguam Pass (24%) 3 (n=18) 4

  35. Aleutian Pass usage – Bogoslof Is pups Samalga Pass Bogoslof Island (n=18) 1 2 3 >= 4 Samalga Pass (33%) (n=17)

  36. Mother-pup departures 10-15d apart 1-5d apart 5-10d apart

More Related