2006 Southern Resident Killer Whale Symposium 

NOAA Fisheries Service Northwest Regional Office 

April 3-5, 2006, Seattle WA 98103 

Extended Abstract 

Regional patterns of persistent organic pollutants in five Pacific salmon 

species (Oncorhynchus spp) and their contributions to contaminant 

levels in northern and southern resident killer whales (Orcinus orca) 

O’Neill, Sandra M.1; Ylitalo, Gina M.2; West, James, E.1; Bolton, Jennie2; Sloan, 

Catherine A.2

; Krahn, Margaret M.2

1

Washington Department of Fish and Wildlife, 600 Capitol Way North, Olympia WA 98501-1091 2

 NOAA Fisheries, Northwest Fisheries Science Center, 2725 Montlake Blvd. E., Seattle, WA 98112 

Previous studies on killer whales (Orcinus orca) have shown that southern residents 

contain higher concentrations of persistent organic pollutants (POPs) than northern 

residents (Ross et al., 2000; Rayne et al., 2004) and other North Pacific resident killer 

whale populations (Ylitalo et al., 2001; Herman et al., 2005). Elevated contaminant 

exposure in southern residents may be attributed to dietary differences between the two 

whale populations or to regional differences in concentrations of POPs in their prey. 

Based on observational data and stomach contents analyses, Ford et al. (1998) identified 

Pacific salmon (Oncorhynchus spp), especially Chinook salmon (O. tshawytscha), as the 

primary prey of southern and northern resident killer whales in their summer feeding 

ranges. The main objective of this study was to determine if Pacific salmon had speciesspecific regional body burdens of contaminants that could differentially affect 

contaminant levels is northern and southern residents. An additional objective was to 

measure proximate composition (amount of protein, lipid and carbohydrate) and estimate 

caloric content of Pacific salmon as an indicator of species- and regionally-specific 

variation in nutritional quality of prey to killer whales. 

Free-ranging populations of anadromous Pacific salmon are generally assumed to have 

low levels of POPs because the majority of their growth (and therefore contaminant 

uptake) occurs in open water of the Pacific Ocean. However, the oceanic distributions of 

the five Pacific salmon species (i.e., Chinook, coho, chum, pink, sockeye) differ and, as a 

result, can influence their exposure to contaminants. For example, when pink, chum and 

sockeye salmon enter the marine environment, they rapidly migrate northward and 

westward through coastal waters of North America and are found in the open waters of 

the North Pacific, Gulf of Alaska and Bering Sea by the end of their first year at sea 

(Quinn, 2005). In contrast, Chinook and coho, have a more coastal marine distribution 

along the continental shelf compared to other salmon populations, although, populations 

within these two species can also differ in their marine distribution (Quinn, 2005). 

To determine if Pacific salmon populations present in the summer feeding areas of 

northern and southern resident whales had species- and regionally-specific body burdens 

of contaminants, we analyzed POPs in whole body samples of five species of Pacific 
salmon collected from northern British Columbia to the central California coast. All five 

species were each sampled in two regions, the non-urbanized north-central coast of 

British Columbia that is frequented by northern resident killer whales and in the 

urbanized Puget Sound - Strait of Juan de Fuca region that is frequented more by 

southern resident killer whales (Table 1). Additionally, Chinook salmon were sampled in 

the coastal waters on the inside of Vancouver (near Robson Bight), the Lower Columbia 

River (spring and fall runs) and central coast of California (Table 1). We sampled 

terminal marine and in-river fisheries, at times aligned with the return time for specific 

salmon stocks, to increase the likelihood of sampling particular stocks of fish returning to 

a specific river. The presumed river-stock associated with each sampling location is 

noted in Table 1. 

Table 1. Number of individual fish of each species collected at each sampling location for chemical, 

proximate and stable isotope analyses. Contaminants samples were based on whole body samples of 

individual Chinook salmon and composite samples (5-6 individuals) for other salmon species. Proximate 

analyses were based on composite samples of males or females, each with 2-3 fish per composite. Note: 

Only 13 of the Fraser and 20 of the Columbia River Fall Chinook were analyzed for contaminants but 

proximate analyses were based on all fish collected. 

Fall Spring Resident

Chatam

Sound Skeena 30 29 30

Dean

Channel Kimsquit 30 30

East coast

Vancouver

Island

near

Robson

Bight 

Fraser/

Nimpkish 30

Lopez

Sound Fraser 30

Skagit

River Skagit 30

near Apple

Cove Point

Puget Sound 

mixed 34 30 11

Nooksack/

Duwamish/

Nisqually

rivers

Puget Sound 

mixed 36 29

Columbia

River

Lower

Columbia

River Columbia 30 20

Central coast

of California 

near Point 

Arena

Sacramento/

Joaquin 29

Species

River Stock Chinook Sockeye Pink Chum Coho

Origin

Sampling

Region Location

Strait of Juan

de Fuca/ 

Puget Sound

North/ central

coast BC
Overall, concentrations of POPs were higher in coho and Chinook populations that have 

more coastal distributions than those measured in salmon species (e.g., chum, pink, 

sockeye) with more oceanic distributions. For pink, chum, and sockeye salmon, PCB 

levels were higher for fish caught in the more urbanized region of Puget Sound/Strait of 

Juan de Fuca region than in the less urbanized north/central coast of British Columbia 

area, whereas concentrations of DDTs were similar between regions. PBDEs were 

below the limit of quantitation in all pink, chum and sockeye sampled in this study. 

Concentrations of PCBs, PBDEs and DDTs were higher in coho salmon from Puget 

Sound compared to coho from the central BC coast. Regional variation in POP exposure 

was also evident in Chinook salmon (Figure 1) and appears to be associated with 

differences in marine distribution of these species. For example, Chinook salmon 

returning to Puget Sound had significantly higher concentrations of PCBs and PBDEs ng/g wet weight

0

20

40

60

80

100

Spring Run Chinook

Fall Run Chinook

Resident Chinook

ng/g wet weight

0

10

20

30

40

50

ng/g wet weight

0

10

20

30

40

50

central 

 CA

Columbia

River

 Puget 

 Sound

eastern

Vanc. I.

northern

BC

 <1ppb <1ppb

PCBs

PBDEs

DDTs

Figure 1. Concentrations of persistent organic pollutants (+ 95% CI) in whole body samples of individual

Chinook salmon caught in terminal fishing areas. River populations represented include fish returning to

the Sacramento/San Joaquin (central CA; n = 29), the Columbia River (spring run n = 20; fall run n = 17),

the Nooksack, Duwamish and Nisqually (Puget Sound; n = 36), the Fraser and Nimpkish (eastern coast 

Vancouver Island; n = 13;Georgia Basin) and the Skeena rivers (northern BC; n= 30). Additionally data are 
shown for sub-adult chinook salmon that were resident in Puget Sound in the winter months (termed 

“resident chinook” n= 34). 

compared to other Pacific coast salmon populations we sampled. Furthermore, Chinook 

salmon that resided in Puget Sound in the winter rather than migrate to the Pacific Ocean 

(“residents”) had the highest concentrations of POPs, followed by Puget Sound fish 

populations believed to be more ocean-reared. Fall Chinook from Puget Sound have a 

more localized marine distribution in Puget Sound and the Georgia Basin than other 

populations of Chinook from the west coast of North America and are more contaminated 

with PCBs (2 to 6 times) and PBDEs (5 to 17 times). 

Overall, the total caloric content per kg of fish was higher for Chinook and sockeye 

salmon than the other salmon species we sampled, due to their higher fat content. 

Moreover, because of their greater size, the total Kcal per fish was highest for Chinook 

salmon. Regional differences in caloric content among Chinook populations were also 

observed. Puget Sound Chinook had lower caloric content (total Kcals per fish) than 

summer/fall run of Chinook salmon from all regions we sampled (Figure 2). Assuming 

that the fish we sampled were representative of the sizes of fish available for killer whale 

consumption, whales feeding on non-resident Chinook salmon in Puget Sound would 

need to eat 1.5 to 1.8 times as many Chinook salmon as animals feeding outside Puget 

Sound to obtain the same caloric content.

Average Kcal per Fish

0

5000

10000

15000

20000

25000

Spring Run Chinook

Fall Run Chinook

Resident Chinook

 central

 CA

Columbia 

River

 Puget 

 Sound

eastern

Vanc. I.

 northern

BC

Figure 2. Average estimated caloric content (+ 95% CI) of whole body samples of individual Chinook

salmon caught in terminal fishing areas. River populations represented include fish returning to the

Sacramento/San Joaquin (central CA), the Columbia River (spring and fall runs), the Nooksack, Duwamish 

and Nisqually (Puget Sound), the Fraser and Nimpkish (eastern coast Vancouver Island) and the Skeena

rivers (northern BC). 

 In summary, regional body burdens of contaminants in Pacific salmon, and Chinook 

salmon in particular, could contribute to the higher levels of contaminants in southern 

resident killer whales. In addition to contamination, regional differences in caloric 

content of Chinook salmon from Puget Sound further reduce their quality as prey to 

southern resident killer whales. 
References 

Ford JKB, Ellis GM, Barrett-Lennard LG, Morton AB, Palm RS, Balcomb III KC. 1998. 

Dietary specialization in two sympatric populations of killer whales (Orcinus

orca) in coastal British Columbia and adjacent waters. Can. J. Zool. 76(8): 1456-

1471. 

Herman, D.P., Burrows, D.G., Wade, P.R., Durban, J.W., LeDuc, R.G., Matkin, C.O., & 

Krahn, M.M. (2005) Feeding ecology of eastern North Pacific killer whales from 

fatty acid, stable isotope, and organochlorine analyses of blubber biopsies. Mar. 

Ecol. Prog. Ser. 302: 275-291. 

Quinn TP, 2005. The Behavior and Ecology of Pacific Salmon and Trout. American 

Fisheries Society, University of Washington Press, Seattle, Washington. 378 pp. 

Rayne S, Ikonomou MG, Ross PS, Ellis GM, Barrett-Lennard LG. 2004. PBDEs, PBBs, 

and PCNs in three communities of free-ranging killer whales (Orcinus orca) from 

the northeastern Pacific Ocean. Environ. Sci. Technol. 38(16): 4293-4299. 

Ross PS, Ellis GM, Ikonomou MG, Barrett-Lennard LG, Addison RF. 2000. High PCB 

concentrations in free-ranging Pacific killer whales, Orcinus orca: Effects of age, 

sex and dietary preference. Mar. Pollut. Bull. 40(6): 504-515. 

Ylitalo, GM, Matkin CO, Buzitis J, Krahn MM, Jones LL, Rowles T, Stein JE. 2001. 

Influence of life-history parameters on organochlorine concentrations in freeranging killer whales (Orcinus orca) from Prince William Sound, AK. Sci. Total 

Environ. 281: 183-203.