Declining spring usage of core habitat by endangered fish-eating killer whales reflects decreased availability of their primary prey
Monika W. Shields A C , Jimmie Lindell A B and Julie Woodruff A
+ Author Affiliations
- Author Affiliations
A Orca Behavior Institute, c/o 573 Westcott Drive, Friday Harbor, WA 98250, USA.
B University of Gothenburg, 405 30 Gothenburg, Sweden.
C Corresponding author. Email: monika@orcabehaviorinstitute.org
Pacific Conservation Biology 24(2) 189-193 https://doi.org/10.1071/PC17041
Submitted: 29 October 2017 Accepted: 9 April 2018 Published: 15 May 2018
Abstract
The salmon-eating Southern Resident killer whales (Orcinus orca) of the north-eastern Pacific Ocean are listed as endangered both in the United States and Canada. Their critical habitat has been defined as the region of the inland waters of Washington State and British Columbia known as the Salish Sea, where they have traditionally spent much of their time from spring through fall. Using reports from experienced observers to sightings networks, we tracked the daily presence of the Southern Residents in these waters from 1 April to 30 June from 1994 through 2016. We found that the escapement estimates of spring Chinook salmon (Oncorhynchus tshawytscha) on the Fraser River in British Columbia were a significant predictor of the cumulative presence/absence of the whales throughout the spring season. There was also a difference in both whale presence and salmon abundance before and after 2005, suggesting that the crash in Chinook salmon numbers has fallen below threshold where it is worthwhile for the whales to spend as much time in the Salish Sea. The use of the Salish Sea by the Southern Residents has declined in the spring months as they are either foraging for Chinook salmon elsewhere or are shifting to another prey species. In order to continue providing necessary protections to this endangered species, critical habitat designations must be re-evaluated as this population of killer whales shifts its range in response to prey availability.
Additional keywords: Chinook salmon, critical habitat, Orcinus orca, prey availability, Salish Sea
References
Bailey, R. E., Parken, C. K., Irvine, J. R., Rosenberger, B., and Farwell, M. K. (2000). Evaluation of utility of aerial overflight based estimates versus mark–recapture estimates of chinook salmon escapement to Nicola River, BC. Canadian Stock Assessment Secretariat 2000/152.Bailey, R. E., Irvine, J. R., Candy J. R., Parken, C. K., Lemke, S. L., Sullivan, M., and Wetklo, M. (2001). Summary of stock assessment information for selected early returning Chinook salmon populations of the Fraser River watershed. Canadian Science Advisory Secretariat 2001/134.
Cimino, L., and Lovari, S. (2003). The effects of food or cover removal on spacing patterns and habitat use in roe deer (Capreolus capreolus). Journal of Zoology 261, 299–305.
| The effects of food or cover removal on spacing patterns and habitat use in roe deer (Capreolus capreolus).Crossref | GoogleScholarGoogle Scholar |
Dulvy, N. K., Sadovy, Y., and Reynolds, J. D. (2003). Extinction vulnerability in marine populations. Fish and Fisheries 4, 25–64.
| Extinction vulnerability in marine populations.Crossref | GoogleScholarGoogle Scholar |
Felleman, F. L., Heimlich-Boran, J. R., and Osborne, R. W. (1991). The feeding ecology of killer whales (Orcinus orca) in the Pacific Northwest. In ‘Dolphin Societies: Discoveries and Puzzles’. (Eds K. Pryor and K. S. Norris.) Chapter 3, pp. 113–147. (University of California Press: Berkeley.)
Fisheries and Oceans Canada (2011). Recovery strategy for the northern and southern resident killer whales (Orcinus orca) in Canada. Species at Risk Act Recovery Strategy Series, Fisheries and Oceans Canada, Ottawa.
Ford, M. J. (Ed.) (2011). Status review update for Pacific salmon and steelhead listed under the Endangered Species Act: Pacific Northwest. US Department of Commerce, NOAA Technical Memorandum NMFS-NWFSC-113.
Ford, J. K., and Ellis, G. M. (2005). Prey selection and food sharing by fish-eating ‘resident’ killer whales (Orcinus orca) in British Columbia. Fisheries and Oceans Canada Research Document 2005/041.
Ford, J. K., and Ellis, G. M. (2006). Selective foraging by fish-eating killer whales Orcinus orca in British Columbia. Marine Ecology Progress Series 316, 185–199.
| Selective foraging by fish-eating killer whales Orcinus orca in British Columbia.Crossref | GoogleScholarGoogle Scholar |
Ford, J. K., Ellis, G. M., Barrett-Lennard, L. G., Morton, A. B., Palm, R. S., and Balcomb, K. C. (1998). Dietary specialization in two sympatric populations of killer whales (Orcinus orca) in coastal British Columbia and adjacent waters. Canadian Journal of Zoology 76, 1456–1471.
| Dietary specialization in two sympatric populations of killer whales (Orcinus orca) in coastal British Columbia and adjacent waters.Crossref | GoogleScholarGoogle Scholar |
Ford, J. K., Ellis, G. M., and Balcomb, K. C. (2000). ‘Killer Whales: The Natural History and Genealogy of Orcinus orca in British Columbia and Washington.’ (UBC Press.)
Ford, J. K., Ellis, G. M., Olesiuk, P. F., and Balcomb, K. C. (2010). Linking killer whale survival and prey abundance: food limitation in the oceans’ apex predator? Biology Letters 6, 139–142.
| Linking killer whale survival and prey abundance: food limitation in the oceans’ apex predator?Crossref | GoogleScholarGoogle Scholar |
Gustafson, R. G., Waples, R. S., Myers, J. M., Weitkamp, L. A., Bryant, G. J., Johnson, O. W., and Hard, J. J. (2007). Pacific salmon extinctions: quantifying lost and remaining diversity. Conservation Biology 21, 1009–1020.
| Pacific salmon extinctions: quantifying lost and remaining diversity.Crossref | GoogleScholarGoogle Scholar |
Hanson, M. B., Baird, R. W., Ford, J. K., and Balcomb, K. C. (2010). Species and stock identification of prey consumed by endangered southern resident killer whales in their summer range. Endangered Species Research 11, 69–82.
| Species and stock identification of prey consumed by endangered southern resident killer whales in their summer range.Crossref | GoogleScholarGoogle Scholar |
Hauser, D. D., VanBlaricom, G. R., Holmes, E. E., and Osborne, R. W. (2006). Evaluating the use of whalewatch data in determining killer whale (Orcinus orca) distribution patterns. The Journal of Cetacean Research and Management 8, 273–281.
Hauser, D. D., Logsdon, M. G., Holmes, E. E., VanBlaricom, G. R., and Osborne, R. W. (2007). Summer distribution patterns of southern resident killer whales Orcinus orca: core areas and spatial segregation of social groups. Marine Ecology Progress Series 351, 301–310.
| Summer distribution patterns of southern resident killer whales Orcinus orca: core areas and spatial segregation of social groups.Crossref | GoogleScholarGoogle Scholar |
Hazen, E. L., Jorgensen, S., Rykaczewski, R. R., Bograd, S. J., Foley, D. G., Jonsen, I. D., Shaffer, S. A., Dunne, J. P., Costa, D. P., and Crowder, L. B. (2013). Predicted habitat shifts of Pacific top predators in a changing climate. Nature Climate Change 3, 234–238.
| Predicted habitat shifts of Pacific top predators in a changing climate.Crossref | GoogleScholarGoogle Scholar |
McCluskey, S. (2006). Population trends and movement complexity patterns of southern resident killer whales (Orcinus orca) in relation to Pacific salmon (Oncorhynchus spp.) in the inland waters of Washington State and British Columbia. M.S. Thesis, University of Washington, Seattle.
National Marine Fisheries Service (2008). Recovery plan for southern resident killer whales (Orcinus orca). National Marine Fisheries Service, Northwest Region, Seattle.
Noren, D. P., and Hauser, D. D. W. (2016). Surface-based observations can be used to assess behavior and fine-scale habitat use by an endangered killer whale (Orcinus orca) population. Aquatic Mammals 42, 168–183.
| Surface-based observations can be used to assess behavior and fine-scale habitat use by an endangered killer whale (Orcinus orca) population.Crossref | GoogleScholarGoogle Scholar |
Osborne, R. W. (1999). A historical ecology of Salish Sea resident killer whales (Orcinus orca): with implications for management. Ph.D. Thesis, University of Victoria, Victoria, BC.
Pacific Salmon Commission (2017). Annual report of catch and escapement for 2016 report TCChinook (17)-2. Pacific Salmon Commission Joint Chinook Technical Committee.
Salzman, J. (1990). Evolution and application of critical habitat under the Endangered Species Act. The Harvard Environmental Law Review 14, 311–342.
Stachura, M. M., Mantua, N. J., and Scheuerell, M. D. (2014). Oceanographic influences on patterns in North Pacific salmon abundance. Canadian Journal of Fisheries and Aquatic Sciences 71, 226–235.
| Oceanographic influences on patterns in North Pacific salmon abundance.Crossref | GoogleScholarGoogle Scholar |
Tompkins, A., and Baxter, B. (2015). Pacific salmon escapement estimation methods for Canada. NPAFC Doc. 1604. Fisheries and Oceans Canada.
Waples, R. S., and Teel, D. J. (1990). Conservation genetics of Pacific salmon I. Temporal changes in allele frequency. Conservation Biology 4, 144–156.
| Conservation genetics of Pacific salmon I. Temporal changes in allele frequency.Crossref | GoogleScholarGoogle Scholar |
Ward, E. J., Holmes, E. E., and Balcomb, K. C. (2009). Quantifying the effects of prey abundance on killer whale reproduction. Journal of Applied Ecology 46, 632–640.
| Quantifying the effects of prey abundance on killer whale reproduction.Crossref | GoogleScholarGoogle Scholar |
Wasser, S. K., Lundin, J. I., Ayres, K., Seely, E., Giles, D., Balcomb, K., Hempelmann, J., Parsons, K., and Booth, R. (2017). Population growth is limited by nutritional impacts on pregnancy success in endangered southern resident killer whales (Orcinus orca). PLoS One 12, e0179824.
| Population growth is limited by nutritional impacts on pregnancy success in endangered southern resident killer whales (Orcinus orca).Crossref | GoogleScholarGoogle Scholar |
Worm, B., and Tittensor, D. P. (2011). Range contraction in large pelagic predators. Proceedings of the National Academy of Sciences of the United States of America 108, 11942–11947.
| Range contraction in large pelagic predators.Crossref | GoogleScholarGoogle Scholar |
