Seven Southern Resident Killer Whales Missing!
The southern resident killer whale population (SRKW) is near and dear to us all. In fact, this population of the Pacific Northwest’s most magnificent marine mammals is what brought me to the San Juan Islands more than thirty years ago, with a US government contract to see whether what the late Dr. Mike Bigg said was true. Mike claimed, and later unequivocally verified, that each and every killer whale in the Pacific Northwest could be individually photo-identified; therefore, we could know the status of the regions most charismatic icon then, and forevermore. This website is dedicated to providing all of the information we have gathered about these whales since Mike’s discovery that whales can be individually recognized.
We always knew that the SRKW’s eat salmon – fishermen used to shoot them to get rid of the competition. Now, we know that these whales predominantly eat Chinook salmon (O. tsawytscha), and that is not surprising because these are large nutritious fish that were historically and prehistorically very abundant year-round. We also know that many populations (ESU’s in scientific and government-speak) of Chinook salmon from California to British Columbia are threatened with extinction, if not already extinct, and many are recently declining in many parts of their range (see NOAA Fisheries Chart http://www.nmfs.noaa.gov/pr/pdfs/criticalhabitat/chinooksalmon.pdf, and http://seattletimes.nwsource.com/html/localnews/2004387400_salmon02.html ). This is a tragedy for the Chinook, the fishermen, and the whales. I am going to largely restrict my comments to the tragedy for whales, though I am not insensitive to the plight of fish and humans.
The evidence indicates that about 96% of the diet of SRKW’s consists of salmon, with 71% being Chinook salmon and 22% being Chum salmon (O. keta in autumn). Some estimates put the percentage of Chinook in the annual diet as high as 80%. Coho (O. kisutch), Pink (O. gorbuscha), Sockeye salmon (O. nerka), and Steelhead (O. mykiss), though seasonally abundant in some regions, comprise only about 5% of the known diet of SRKW’s. [For a description and status of all of these salmonids see http://www.nwr.noaa.gov/ESA-Salmon-Listings/ . ]
Killer whales are large dolphins, and diet studies of these animals indicate that they consume about 2.5 to 5% of their body weight of suitable prey species per day. I have calculated that the 83 killer whales in the SRKW population have a total biomass of about 638,000 pounds and probably eat about 25,000 pounds of fish per day in aggregate. That is a lot of fish!... more than 1,200 nice 20 pound fish per day! 438,000 fish per year! Compare that, however, to the historical catch of Chinook salmon by humans over the past thirty years (data from Pacific Fisheries Management Council:
Clearly, human harvests of Chinook salmon over the most recent three decades have been two to nine times the consumption by SRKW’s (catches down from over 3.5 million Chinook caught in 1976 to less than one million Chinook caught in 1999. Currently, the Chinook catches are even lower, and the long term forecast: “wild salmon in California and Pacific Northwest almost assuredly will be reduced even further by 2100.” (Salmon 2100: The Future of Wild Pacific Salmon, American Fisheries Society, 2006). “The causes have been, and in many cases still are 1) Intense commercial, recreational, and subsistence fishing, and especially since the 1990’s, mixed stock fishing; 2) Freshwater and estuarine habitat alteration due to urbanizing, farming, logging, and ranching; 3)Dams built and operated for electricity generation, flood control, irrigation, and other purposes.” The list continues with virtually no disagreement among the experts. The abundance of Chinook salmon in this region in 1900 was more than twelve million adult salmon returning to spawn each year.
Then, compare this graph of the SRKW population status in the Spring of 2008:
From 1976 until around 1981 the SRKW’s were recovering from the removal of several dozen young whales for aquaria and marine parks, hence their population size would have been much larger (probably over one hundred) prior to 1981 had the removals not occurred.
My considered opinion is that the total number of Chinook salmon required to be available for the SRKW’s, and the ecosystem, is on the order of two and a half million adult fish per year, and that a recovery goal for both SRKW’s and Chinook salmon in the region is on the order of five million adult fish per year (roughly the number of Chinook salmon CAUGHT by fishermen in the Columbia River alone from the mid to late 1800’s!). Regrettably, we cannot turn back the clock to those times prior to 1900, and there are many obstacles, including dams, in the way of Chinook salmon restoration to viable population levels; but, it is imperative for the survival of both Chinook salmon and SRKW’s that our society (US and Canada, First Nation and Arrivals) make the effort to restore these icon species to functional levels in the ecosystem. It is not just the fish and the whales at stake, it is our own survival slipping away. The missing whales are:
J43 first seen 2007/11/06 last seen 2007/11/24
K7 last seen 2007/12/23
L21 last seen 2008/06/29 west entrance Strait of Juan de Fuca; 2008/06/21 Haro
L101 last seen 2008/01/27 Monterey, CA
J11 last seen 2008/07/19
L111 first seen 2008/08/12 last seen 2008/08/21
L67
That list accounts for seven whales that have died in a twelve month period, tying the record for SRKW deaths in 1999 as the worst survival period in the history of our study. This year is not over and the population number by 31 December may change again. These numbers are examined statistically in several different ways, so do not take this as a summary of 2008 just yet. What we present is a twelve month running summary that will be updated to a calendar year summary after the 31 December population size is determined. The statistical comparison to the population size of the Northern Resident Killer Whales (NRKW’s) is made as of 1 July each year.
POSTED: 12:00 p.m. November 4, 2008
