SPLASH

The “Structure of Populations, Levels of Abundance, and Status of Humpbacks,” project, also known as “SPLASH”, is a three-year study focusing on important questions about humpback whales in the North Pacific. This is a multinational, collaborative effort involving over 150 researchers, from over ten countries. Why is this important?

Humpback whales in the North Pacific are thought to have been reduced from pre-whaling numbers of 15,000 to less than 1,000 animals [1, 2] shortly after their protection in 1966. Some evidence exists that populations in some areas have recovered substantially [3-6]. However, limited information exists on the current and overall status and population of humpback whales in the North Pacific.

Although commercial whaling no longer poses a major threat to the humpback’s survival, little is known about the effect of other threats such as climate change, global warming, vanishing food resources, pollution, entanglement, and ship strikes are having or will have on their continued recovery.

This international, collaborative 3-year study began in the winter of 2004. Results from this study will attempt to answer these very important questions:

• 1. What are current population estimates for specific feeding and breeding areas, and for the North Pacific population as a whole?
• 2. Are these populations increasing or decreasing each year?
• 3. What are their migratory patterns?
• 4. How does the genetic stock structure of the whale differ geographically?
• 5. What are the reproductive and mortality rates?
• 6. What is the sex ratio in the population?
• 7. What are the pregnancy rates in the population?
• 8. Which habitats are most important and how are they being used by different sexes and age classes?
• 9. How often do whales survive entanglements and ship strikes?
• 10. What concentrations of contaminants exist in the blubber?

How do we answer these questions?

Two primary sources of data are being collected. These include photo-identifications and biopsy samples.

Method

A consistent sampling effort is taking place over broad geographic areas, in both the winter/breeding grounds and the summer/feeding grounds. The amount of effort allocated to an area is proportional to the density of the animals in that area. The goal is to photo-identify ten percent of the population in these areas, during each year of effort. A similar effort carried out in the North Atlantic named Years of the North Atlantic Humpback (YoNAH) project [7] is providing valuable guidelines for target sample sizes. Target sample sizes for all winter/breeding areas is 500 tissue samples and 1,000 tissue samples for all summer/feeding areas.

Feeding areas include the coast of California, north to the Gulf of Alaska, west across the Bearing Sea, and south to Hokkaido in Northern Japan. Breeding areas include Central America [8], Mexico [9], Hawaii, Japan [10], and the Philippines.

• 1. Population estimates will be done through the matching of fluke photo-identifications and genetic markers. A mark-recapture model used by Calambokidis et al. [6] will be applied to generate the best estimate. Although several mark-recapture models exist, this model has proven to be the most applicable to this study [11, 12].
• 2. Annual population trends will be assessed using similar methods to Calambokidis et al. [6], and compared with 1991-1993 trends.
• 3. Migration destinations will be determined through both photographic matching, and matching using genetic markers (mitochondrial DNA, microsatellite loci).
• 4. Genetic stock structures will be evaluated, using DNA sequence comparisons from skin tissue samples.
• 5. Reproductive rates will be determined through observations of mothers with calves. These reproductive rates will be compared with mortality rates to determine population trends.
• 6. Sex ratios will be determined via DNA sequencing.
• 7. Pregnancy rates will be assessed from tissue samples, and compared with calving rates, to determine reproductive success.
• 8. Tissue samples and behavioral data will be used to determine habitat preferences by different sex and age classes.
• 9. The threat of entanglement in fishing gear will be assessed from photographed entanglement scars. This assessment will then be correlated to age, sex, and geographic region using similar analyses to that of the Gulf of Maine [13].
• 10. Samples containing blubber will be analyzed for contaminant levels.

Additionally, the photo-identification and genetic archives developed from this study will continue to be used in future research and conservation efforts.

Click here for summary of results...

Literature Cited

1. Johnson, J.H. and A.A. Wolman, The humpback whale, Megaptera novaeangliae. 1984.

2. Rice, D.W., The humpback whale in the North Pacific: distribution, exploitation, and numbers., in Report on a workshop on problems related to humpback whales (Megaptera novaeangliae), in Hawaii, K.S.N.R. Reeves, Editor. 1978, U.S. Marine Mammal Commission: Washington, D.C. p. 29-44.

3. Calambokidis, J., et al., Research on humpback and blue whales off California, Oregon, and Washington in 2001. 2002, Cascadia Research: 2181⁄2 W Fourth Ave., Olympia, WA 98501 . p. 50.

4. Mobley, J.R., Jr., G.B. Bauer, and L.M. Herman, Changes over a ten-year interval in the distribution and relative abundance of humpback whales (Megaptera novaeangliae) wintering in Hawaiian waters. Aquatic Mammals, 1999. 25(2): p. 63-72.

5. Calambokidis, J., et al., Migratory destinations of humpback whales that feed off California, Oregon and Washington. Marine Ecology Progress Series, 2000. 192: p. 295-304.

6. Calambokidis, J., et al., Abundance and population structure of humpback whales in the North Pacific basin. 1997, Southwest Fisheries Science Center: P.O. Box 271, La Jolla, CA 92038. p. 72.

7. Smith, T.D., et al., An ocean-basin-wide mark-recapture study of the North Atlantic humpback whale (Megaptera novaeangliae). Marine Mammal Science, 1999. 15(1): p. 1-32.

8. Steiger, G.H., et al., Movement of humpback whales between California and Costa Rica. 1991.

9. Urban, R.J. and L.A. Aguayo, Spatial and Seasonal Distribution of the Humpback Whale Megaptera-Novaeangliae in the Mexican Pacific. Marine Mammal Science, 1987. 3(4): p. 333-344.

10. Darling, J.D. and K. Mori, Recent observations of humpback whales (Megaptera novaeangliae) in Japanese waters off Ogasawara and Okinawa. Canadian Journal of Zoology, 1993. 71(2): p. 325-333.

11. Darroch, J.N., The two-sample capture-recapture census when tagging and sampling are stratified. Biometrika, 1961. 48: p. 241-260.

12. Hilborn, R., Determination of fish movement patterns from tag recoveries using maximum likelihood estimators. Canadian Journal of Fisheries and Aquatic Sciences, 1990. 47: p. 635-643.

13. Robbins, J. and D. Mattila, Monitoring entanglements of humpback whales (Megaptera novaeangliae) in the Gulf of Maine on the basis of caudal peduncle scarring. 2001, IWC Scientific Committee Meeting: Hammersmith, UK.

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