Modern status of Sea otter population on the Commander Islands Alexander Burdin, Kamchatka branch of Pacific Institute of Geography, RAS, University of Alaska, Fairbanks, ASLC, Sergey Zagrebelny, Commander preserve Commander Population declines Islands (population growing) Background Only 200 nm strait between Commander Island and western Aleutian islands. Dramatic decline of sea otter populations (up to 90% and more reduction), and some other marine mammal species (harbor seal, SSL) across the Aleutian Archipelago and Alaska Peninsula during past several decades. Increasing (13%/year) sea otter population on the Commander Islands. Research Objectives Commander-Aleutian islands c comparisonsomparisons 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-kelp 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 Bering Island Totally 33 sea otters 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. Ecosystem 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 animals). 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 ottermortalityand birthrate(%%)ontheBeringIsland % 10 15 20 25 30 0 5 1980 1982 1984 1986 1988 1980- 2005 1990 1992 1994 1996 1998 2000 2002 2004 mortality birthrate Dynamics of sea otter population on the Commander Isla 8000 7000 6000 5000 4000 3000 (Bering and Medny) in 1985-2007 2000 1000 0 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 n 1995 1996 yea 1997 r 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 100 200 300 400 500 600 700 800 300 400 500 600 700 800 100 200 0 0 6/15/056/15/05 253253 6161 6/17/05 Daily seaotterdynamicsontheNWcape (BeringIsl.)insummer2005. 6/17/05 313313 Daily seaotterdynamicsontheNWcape (BeringIsl.)insummer2005. 487487 6/19/056/19/05 379379 484484 6/21/056/21/05 393393 420420 6/23/056/23/05 169169 353353 6/25/056/25/05 218218 497497 6/29/056/29/05 433433 543543 301301 7/1/057/1/05 430430 7/4/057/4/05 441441 400400 255 date 255 date 7/6/057/6/05 551551 7/8/057/8/05 663663 698698 7/11/057/11/05 579579 452452 7/14/057/14/05 244244 517517 7/16/057/16/05 430430 334334 7/18/057/18/05 232232 326326 7/20/057/20/05 594594 22 7/25/057/25/05 174174 404404 7/27/057/27/05 200200 219219 7/30/057/30/05 189189 7474 8/1/058/1/05 423423 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 killer whale attacks happened in specific place and for specific prey. “Shield” Northern fur 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 fur seal 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 northern fur seal 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 mammals 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 marine mammal declines. Thank you! Photo by R. Davis.