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PVOA Sunny Rice, Marine Advisory Agent, UAF Outline 1) Background - PowerPoint PPT Presentation

Nov 07, 2022 •504 likes •872 views

Recolonization, prey selection and resource competition by sea otters, Enhydra lutris , in southern southeast Alaska. Zac Hoyt, PhD student, UAF Verena Gill, Wildlife Biologist, USFWS Ginny Eckert, Professor, UAF PVOA Sunny Rice, Marine

  1. Recolonization, prey selection and resource competition by sea otters, Enhydra lutris , in southern southeast Alaska. Zac Hoyt, PhD student, UAF Verena Gill, Wildlife Biologist, USFWS Ginny Eckert, Professor, UAF PVOA Sunny Rice, Marine Advisory Agent, UAF

  2. Outline 1) � Background – Sea otter biology A) � Historic and current distribution of sea otter in the N Pacific, AK, SE AK, and finally SSE AK. B) � Current distribution and growth of SSE AK otter pop. C) � Resource competition in SE AK

  3. Outline 1) � Background – Sea otter biology A) � Historic and current distribution of sea otter in the N Pacific, AK, SE AK, and finally SSE AK. B) � Current distribution and growth of SSE AK otter pop. C) � Resource competition in SE AK 2) � Foraging A) � Calculate proportion of sea otter diet of commercially important macro invertebrates in SSE AK.

  4. Outline 1) � Background – Sea otter biology A) � Historic and current distribution of sea otter in the N Pacific, AK, SE AK, and finally SSE AK. B) � Current distribution and growth of SSE AK otter pop. C) � Resource competition in SE AK 2) � Foraging A) � Calculate proportion of sea otter diet of commercially important macro invertebrates in SSE AK. B) � Differences in sea otter diet on a spatial scale relating to current sea otter distribution.

  5. The only marine mammals without blubber Sea otters have a high metabolism

  6. Sea otter predators Orcas Sharks Eagles

  7. Only 1 pup/year. Rare twinning.

  8. Population of sea otters ranged from 200,000 – 300,000 pre fur trade

  9. 1000 -2000 sea otters in � 1911

  10. Present population 85,000 individuals Current estimate 82,350-95,000 sea otters

  11. Alaska (73,000+) in 3 stocks USFWS 2009

  12. Translocation Sites � � Cape Spencer � � Yakobi Island � � Khaz Bay � � Biorka Island � � Maurelle Islands � � Barrier Islands 51 55

  13. 1960’s Release Maurelle Islands 51 otters Barrier Islands 55 otters 2003 Population � � Southern portion (2003) estimated at 5,845 otters � � SE = 821 � � SE AK Esslinger and Bodkin 2009

  14. Survey completed July / Aug. for SSE AK Aerial Survey method Systematic transects, stratified design, with a calculated site ability factor

  16. Results 2010 Growth rate = 13% annually Abundance estimate = In review

  17. 2010 13% annual increase since 2003 5,845 otters in 2003

  18. Sea otter harvest levels in SE AK 1989-2010 *

  19. Resource Conflicts

  20. Fisheries affected in southern SE AK - value $16 million dollar (2008 -09) Red Sea Urchin , Strongylocentrotus Dungeness Crab, Metacarcinus franciscanus magister (formerly Cancer magister) California Sea Cucumber, Geoduck Clam, Panopea abrupta Parastichopus californicus

  21. Fisheries Interactions Sea otter abundance YEAR

  22. Foraging data collection

  23. The sea otter diet is extremely diverse Specialists and generalists. High metabolic rate so can eat up to 23% of body weight

  24. Forage in shallow water (0-100 m)

  25. 50 mm 1.5 paw Telmessus cheiragonus Coded = TEC – 2b Foraging

  26. 2010 Field Work

  27. Results Otter foraging success 116 bouts recorded 1500 dives recorded 1332 successful

  28. Diet composition by taxonomic group

  29. Other commercially important species Pandalus spp. - 2 % Tanner Crab, Chionoecetes bairdi - < 1% Red king crab , Paralithodes camtschaticus Pinto Abalone , Haliotis kamtschatkana

  30. Commercial Component of Sea Otter Diet Proportion of observed diet 108 bouts, 1332 dives

  31. Spatial differences in diet 1) � Colonization history 2) � H o : Commercially important component of diet does not differ by otter colonization history

  32. z= -3.114, p=0.0018 Proportion of observed diet Otters present before 2003 Otters present since 2003 z= 5.121, p<0.0002 z= -1.85, p=0.643

  33. Proportion of observed diet Observed proportion of diet z= 5.121, z= 5.87, No statistical power p<0.0002 p<0.0002

  34. Conclusion • � Results confirm what we have been hearing anecdotally from the commercial fleet. • � Otters are having a significantly greater effect on commercial macro invertebrates on the frontal boundaries of their current distribution especially relating to California Sea Cucumbers and Dungeness Crab. • � More foraging data is needed from the region to address conflict of the other commercially important species.

  35. What’s next • � Continue forage sampling in 2011 • � Caloric/ biomass scale • � Fisheries assessment analysis, depletion rates, spatial scale and economic impacts • � NPRB project Goal: Examine interactions between sea otter population & prey, small- scale distribution, movement, & prey selection on the recolonizing front of the SSE AK population

  36. Special Thanks Icicle Seafood's Kake Tribal USFS - Petersburg Ranger District Bonnie Greenwood Tory Wilson Marlene Wagner Crew of the F/V’s: Kuprenof Kamalar Westerly PERMITS : MMPA permit #041309 Deco Bay IACUC 164017-1

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