Body condition of western gray whales in relation to environmental change in the North Pacific

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1 Body condition of western gray whales in relation to environmental change in the North Pacific Hyun Woo Kim 1, 4, David W. Weller 2, Amanda L. Bradford 3 and Zang Geun Kim 4 1 Pukyong National University, Busan, Korea 2 Southwest Fisheries Science Center, NOAA Fisheries, La Jolla, California, USA 3 University of Washington, Seattle, Washington, USA 4 Cetacean Research Institute, NFRDI, Ulsan, Korea

2 Introduction Western Gray Whale (Eschrictius robustus) Western & Eastern population (or Korea & California stock) Genetic and geographic isolation from Eastern gray whale

3 Reduced by Commercial Whaling Only small remnant animals survived Estimated total population size approximately 120 indiv. (Cooke et al. 2006) Listed by the IUCN as critically endangered Extinction Potential Assess Health of Western Gray Whales needs

4 Biological characteristics Population and life history studies of most large whale species are difficult because they range widely in the open ocean. Gray whale feed and breed only coastal area shallower then 20m (Rice and Wolman, 1971). They feed only in feeding ground. Mostly feed amphipod.

5 Skinny gray whales were found in 1999 Normal Skinny The most likely cause of this condition is nutritional stress but the underlying reason remains unknown

6 Our hypothesis The skinny whale phenomenon was likely to be linked with oceanic environment changes in the feeding area associated to climate change of the North Pacific.

7 Methods Survey area Photo- Identification method in off Sakhalin Island, Russia - only known main feeding ground???? Long-term survey ( 1995, )

8 Photo Identification method each individuals identified through 3 features. Dorsal hump Patches & Spots 23th, Aug., 2006 The Western gray whale Catalogue match Indiv. I.D. No. 134, Name: Bada

9 Body condition of individual whales Determined using a photo-based method (Pettis et al. 2004) Relative Amount of Subcutaneous Fat in three distinct body regions Three characteristics of Loss of subcutaneous fat 1. Post-Cranial Depression 2. Subdermal Protrusion of Scapula 3. Depression along Lateral Flank

10 Collected environmental data Summer (July - September) mean SST (measured in the field) PDO ( SOI ( Niño Indices ( Amphipod biomass in feeding ground (Fedeev, 2002, 2003, 2004, 2005, 2006)

11 Results Annual survey effort, groups encountered and whales identified 1994 to Year Sampling Period (mo, d) Number of Surveys Hours of Observation Groups Encountered Whales Identified /07-09/ /15-08/ /09-09/ /06-09/ /29-10/ /25-09/ /25-09/ /25-09/ /15-09/ /29-09/ /04 09/ Overall , * 150 individuals identified *Not all of these whales are alive

12 Proportion of body condition of each groups All identified body condition Poor Fair Normal Mother Calf Juvenile

13 Two-sided Chi-square test of independence to evaluate mother, calf and Juvenile χ2 Test Mother Calf Juvenile Adult < < < Remove body condition data of Mother, Calf and Juvenile All identified body condition = Mother Calf Juvenile Poor Fair Normal Adult body condition

14 Percentage of skinny whales (only adult group) % Year

15 SST - Amphipod biomass SST - Skinny whale g/m Amphipod biomass mean SST SST Percentage of skinny whale Skinny whale % r= , n= 5, p<0.1 r=0.47, n=5, p<0.2

16 Amphipod biomass Skinny Whale g/m Skinny whale % 10 0 Amphipod biomass Percentage of skinny whale r= , n= 5, p<0.06 Systematic benthic survey have been conducting since 2001 in gray whale feeding ground

17 PDO index Skinny whale Skinny whale % lagged Sep.-jan. PDO Index Percentage of skinny whale year lagged PDO R= -0.68, n=9, p<0.05-6month lagged Sep. Jan. PDO r= -0.83, n= 9, p<0.01

18 Niño 4, SOI Skinny whale correlation (r value) Niño1+2 Niño 3 Niño 3.4 Niño lag (years) -1year lagged Niño 4 r= -0.95, n=9, p<0.01-1year lagged SOI, r= 0.81, n=9, p< % signigicance 10-1 year lagged SOI Percentage of skinny Skinny whale %

19 Amphipods exhibit temperature-dependent growth and maturation rates. (Highsmith and Coyle, 1991) Warm temperature Low age at reproduction Small adult size Small brood size Reduced life span Cold temperature Long-lived Slow-growing Late-maturing Individuals that reach large size Produce large brood Low amphipod biomass Abundant amphipod biomass

20 Suggested hypothesis Negative PDO phase Positive SOI?? Regional warm water in feeding ground of western gray whale Not enough amphipod biomass Increase in poor body condition

21 Summary The western gray whale is still at only a small remnant The Photo-identification study indicate the environmental effect on the health condition even at low population levels. Strong correlation between global climate change and interannual variability in gray whale body condition Small changes in oceanographic conditions in the Pacific Ocean may affect western gray whale population dynamics. But the mechanisms remain still unclear because of limited field environmental data and study of lower ecosystem level on the feeding ground. Identifying the causes and affect understanding is a big need for the conservation of endangered population.

22 Thank you for your attention