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Modern status of population on the Commander

Alexander Burdin, Kamchatka branch of Pacific Institute of Geography, RAS, University of , Fairbanks, ASLC, Sergey Zagrebelny, Commander preserve Commander Population declines Islands (population growing) Background

„ Only 200 nm strait between Commander and western . „ Dramatic decline of populations (up to 90% and more reduction), and some other marine species (, SSL) across the Aleutian Archipelago and during past several decades. „ Increasing (13%/year) sea otter population on the . Research Objectives

Commander-Aleutian islands comparisonscomparisons

¾ to better understand ultimate reasons for the decline

¾ to characterize physiology, behavior, and demography of sea otter population near K.

¾ to expand studies of sea otter- forest interactions 2004-2005 winter field work Sea otter mortality, disease, physical conditions monitoring: Carcasses collection / capture : „ Age/sex composition „ Necropsy: disease, causes of death, virology, female reproductive tracts, parasites, stomach contents „ Biosampling 2006 summer work on the

Totally 33 sea were caught using nets and release. 2006 summer work on the Bering Island

27 sea otters (22 females and 5 males) were instrumented with TDR and radio tag Ongoing investigation and future research

Goal 1. research: „ long-term changes in near shore communities under sea otter predation. „ availability and abundance of sea otter food recourses. „ analysis of TDR’s data. „ direct observation on feeding sea otters. „ scat analysis. „ Retrospective analysis of sea otter feeding habits on the Commanders. Ongoing investigation and future research

Goal II. Monitoring of sea otter population: „ annual survey (skiff and shore based). „ tracking of radio tagged sea otters (movement and observation on focal feeding ). „ mortality (sex/age composition. cause of mortality, disease monitoring). „ birthrate and survival of young sea otters. Sea Otter Body Condition Comparison

35

30

25

20 Weight (kg) 15

Aleutian females, 2004 10 Commander Isl. females, 2006 Aleutian females, 1960s Aleutian females, 1993 5

0 5 10 15 20 25 Age Results of sea otter survey on the Commander Islands in 2005 and 2007

„ 2005 2007 Total number Total number (with pups) PuPupsps (with pups) Pups

Bering 3948 783 4218 996 Medny 2502 665 2813 779

Total on the Commanders 6450 1448 7031 1775 Sea otter numbers on the Commander Islands. Bering (1) and Medny (2) Islands

1

2 Sea otter mortality and birthrate (%%) on the Bering Island 1980- 2005

30 mortality

25 birthrate

20

% 15

10

5

0 1990 1994 1996 1998 2000 1992 2002 2004 1988 1980 1982 1984 1986 Dynamics of sea otter population on the Commander Islan (Bering and Medny) in 1985-2007

8000 7000 6000 5000 4000 3000 2000 1000 0

5 6 9 0 1 2 6 7 8 2 3 4 5 8 8 9 9 9 9 9 0 0 9 9 987 9 9 9 993 9 9 999 000 0 0 006 1 1 1 1988198 1 1 1 1 19941995199 1 1 1 2 2001200 200 2 2 2 2007 year Daily sea otter dynamics on the NW cape (Bering Isl.) in summer 2005.

800 698 698 700 663 663 594 594 579 600 579 551 551 543 543 517 517 497 497 487 484 487 500 484 441 452 441 452 430 430 430 423 430 420 423 420 400 404 400 404 400 353 433 353 433 334 334 326 326 313 393 313 393 379 379 300 253 253 219 301 219 301 189 189 255 174

200 255 200 174 244 244 232 232 218 218 200 2 200 2 169 100 169 61 61 74 74 0 7/8/05 8/1/05 7/1/05 7/4/05 7/6/05 7/8/05 8/1/05 7/1/05 7/4/05 7/6/05 7/11/05 7/14/05 7/16/05 7/18/05 7/20/05 7/25/05 7/27/05 7/30/05 6/15/05 6/17/05 6/19/05 6/21/05 6/23/05 6/25/05 6/29/05 7/11/05 7/14/05 7/16/05 7/18/05 7/20/05 7/25/05 7/27/05 7/30/05 6/15/05 6/17/05 6/19/05 6/21/05 6/23/05 6/25/05 6/29/05 date Some factors effecting to the sea otter population status on the Commanders vs. Aleutian. Commanders Aleutian

Human activity Low Low

Over/Underestimation of sea otter population Negative Negative abundance in previous years? High survival and birthrate in the past years? Positive Negative

Low mortality rate? Positive Negative

Immigration? ?? Negative

Killer whales pressure as a predator? Negative Positive Hypotheses

„ “Availability, not selectivity” „ All observed transient attacks happened in specific place and for specific prey. „ “Shield” „ Northern seal – is the most common prey of killer whales on the Commander Islands (>200,000 ). „ All recorded KW attacks on the Commander Islands happened close to the northern rookeries and almost all attacks were on Northern Fur Seals. Approximate northern boarder of cookie- cutter shark distribution Commander Islands

Aleutian Islands Conclusion

„ The data we have presented shows that the population dynamics of the sea otter populations is different even in the nearby area (Aleutians/Commander Islands). „ 2007 Complete Sea otter survey on the Commander Islands showed that the sea otter population was over 7,000 animals. Conclusion „ We consider to be the most important prey for transient killer whale predation near the Commander Islands, and other areas where this species is present, protecting other marine species from killer whale predation. „ In areas where fur seals are not abundant or absent, mammal eating Killer whales can be a significant factor of declines. Thank you!

Photo by R. Davis