PCBs and Heavy Metals in Farmed, Escaped and Wild

Overview

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Key numbers

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heavy metals, in fillets from farmed (n = 20), escaped (n = 17), and wild (n = 23) Atlantic salmon
PCBs (0.95 ± 0.48 pg TEQ/g), mercury (56.3 ± 12.9 µg/kg) and arsenic (2.56 ± 0.87 mg/kg) were three
The protein content was slightly higher in wild salmon (16%) compared to the farmed fish (15%),
and the amount of essential amino acids were similar. The fat content of farmed salmon (18%) was
substantially lower (8.9 vs. 24.1%). The omega-6 to omega-3 fatty acid ratio was higher in farmed
acids (16). The increased use of vegetable ingredients in fish feed has also resulted in an altered content
Farmed Atlantic salmon (n = 20) were obtained from Lerøy Aurora, one of the largest farmed
The results are presented on wet weight as arithmetic mean of 10–23 parallels ± standard deviation
were significantly smaller: 3.6 kg (Table 1). Wild Atlantic salmon tended to be longer than both
The proximate composition of the fillet of wild, farmed, and escaped salmon, is shown in Table 2.
(18, 12, and 6%, respectively). The protein content was significantly higher (although the numerical
difference was small; 16 and 15%, respectively) in wild salmon compared to farmed fish (16 and 15%,
the fat content inversely being highest in wild salmon (70%) compared to farmed salmon (61%) and
escaped salmon (67%).
farmed (n = 20), and escaped (n = 17) Atlantic salmon.
farmed (n = 20), and escaped (n = 17) Atlantic salmon.
The fatty acid composition (% of total fatty acids) and the total amount of fatty acids per 100 g
of fillets of wild, farmed, and escaped salmon, are presented in Table 3. Lipids in wild salmon
were significantly higher in wild salmon (6.7 and 14.6%) compared to farmed (2.6 and 4.9%) and
escaped salmon (2.6 and 5.6%), whereas linoleic acid and alpha-linolenic acid were more abundant in
farmed salmon (14.4 and 10.3%) compared to escaped (12.8 and 5.3%) and wild (1.4 and 1.0%) salmon.
Table 3. Fatty acid composition (% of total FAs) and amount (g per 100 g of muscle) in wild (n = 23),
farmed (n = 20) and escaped (n = 17) Atlantic salmon.
Table 4. Glutamic acid was the most abundant amino acids for all groups, with approximately
(Table 5). The level of ICES-6 PCB was also significantly higher in wild salmon compared to its farmed
the major dioxin constituents, accounting for 16 and 24% of the dioxins and furans in wild Atlantic
salmon and 19 and 21% in both farmed and escaped salmon (Figure 2b). The 2,3,7,8 TCDF was the
representing 30, 12, and 20% of sum dioxins and furans. The second highest content of congener of the
furans, 2,3,4,7,8 PCDF, contributed with 8, 14, and 11%. Of the dl-PCBs, the non-ortho congener PCB
for 90, 80, and 82% of the total sum of dl-PCB in fillets of wild, farmed and escaped farmed salmon,
more than 30% of the sum ICES-6 PCB in all groups, whereas PCB 101 and PCB 138 accounted for
Table 5. Contaminants in farmed salmon (n = 10), wild salmon (n = 12), and escaped salmon (n = 10)
Mercury (µg/kg) 56.3 ± 12.9 a 18.1 ± 1.5 c 34.9 ± 3.1 b
Cadmium (mg/kg) 0.01 ± 0.0 0.01 ± 0.0 0.01 ± 0.0
Arsenic (mg/kg) 2.56 ± 0.87 a 0.86 ± 0.1 c 1.68 ± 019 b
(n = 10) 10) salmon.
distribution of dl-PCB, in fillets of wild (n = 12), farmed (n = 10), and escaped (n = 10) Atlantic salmon.
distribution of dl-PCB, in fillets of wild (n = 12), farmed (n = 10), and escaped (n = 10) Atlantic salmon.
(International Council for the Exploration of the Sea) PCBs (ICES-6 PCB) in fillets of wild (n = 12),
(International Council for the Exploration of the Sea) PCBs (ICES-6 PCB) in fillets of wild (n = 12),
farmed (n = 10) and escaped (n = 10) Atlantic salmon (Salmo salar L.).
farmed (n = 10) and escaped (n = 10) Atlantic salmon (Salmo salar L.).

Methods (brief)

purchased from a local fishing company. Fifteen scale samples from each side of the fish, behind the
dorsal fin and above the lateral line, were collected and sent to Norwegian Institute for Nature Research
plastic bags at −50 ◦ C. All analyses were performed on wet weight. The number of fish samples for
different analyses varied depending on the cost of the analytical procedure, with fewer samples for
methods, every other sample was selected for analyses.
The amino acid composition was analyzed by dissolving approximately 200 mg of fish samples in
Samples were analyzed for polychlorinated dibenzo-p-dioxins (PCDD), including 2,3,7,8-
sample clean-up and determination by high-resolution gas chromatography/high-resolution mass
by AkvaplanNiva by a direct mercury analyzer of total mercury (Milestone DMA-80, 660-1660
terminal with DMA-80 PC software quartz boat) by a method based on the EPA method 7473 (33).
All values below or equal to level of quantification (LOQ) were set equal to LOQ.
in Fishery Science; Cadrin, S.X., Friedland, K.D., Waldman, J.R.E., Eds.; Elsevier: Amsterdam, The Netherlands,
Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry; Revision 0; U.S. Environmental
1. Aas, T.S.; Ytrestøyl, T.; Åsgård, T. Utilization of feed resources in the production of Atlantic salmon (Salmo salar)
1. Ytrestøyl, T.; Aas, T.S.; Åsgård, T. Utilisation of feed resources in production of Atlantic salmon (Salmo salar)
1. Friedman, N. Nutritional value of protein from different food sources. J. Agric. Food Chem. 1996, 44, 6–29.

Implications

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised