When fish are foul

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The fish are guilty?

 

http://www.biomedcentral.com/news/20030918/03

 

When fish are foulMigrating salmon transport pollutants from the sea to their

freshwater spawning grounds | By Stuart Blackman

 

 

Salmon are famous for their mass migration from the sea to their freshwater

spawning grounds. Sockeye salmon (Oncorhynchus nerka) live most of their lives

in the North Pacific Ocean, where they accumulate 95% of their biomass. On

reaching reproductive age, they can migrate as far as 1000 km up North American

rivers to spawn in lakes, dying soon afterward and subsequently releasing their

constituents into the freshwater ecosystem. In a brief communication the

September 18 Nature E.M. Krümmel and colleagues at the University of Ottawa

report that this complicated life history means that sockeye salmon can act as

bulk transport vectors for pollutants from the ocean to freshwater systems

(Nature, 424:255-256, September 18, 2003).

 

Krümmel et al. focused on polychlorinated biphenyls (PCBs), which are produced

by industrial processes such as waste incineration and which can be dispersed

directly into the atmosphere or can be washed into aquatic environments.

Seawater typically contains 1 ng of PCBs per liter; 1 gram of salmon body fat

can contain 2500 ng. The authors analyzed sediment from eight Alaskan lakes and

showed that the PCB concentration and accumulation rate in lake sediments

correlated strongly with the density of spawning salmon. PCB concentrations in

Frazer Lake—which has annual salmon returns of 11,700 fish per km2—were 10 times

those of Spiridon Lake, which does not receive spawners. In addition, the PCB

signature from Frazer Lake corresponded to that found in the tissues of the

salmon. The PCBs from Spiridon Lake, however, consisted mainly of lighter forms,

which are readily deposited from atmospheric sources.

 

" Returning sockeye salmon act as 'biological pumps' by transporting contaminants

upstream, where pollutants may affect their offspring and/or predators such as

bears, eagles and humans. Whether these contaminants affect juvenile salmon

survival is yet unknown, but they are suspected of causing immunosuppression.

Ironically, the marine-nutrient pump, which historically has increased

successful recruitment, may now pose a risk to some of these populations, "

conclude the authors.

Links for this article

Sockeye salmon

http://www.nmfs.noaa.gov/prot_res/species/fish/sockeye_salmon.h tml

 

E.M. Krümmel et al., " Delivery of pollutants by spawning salmon, " Nature,

424:255-256, September 18, 2003.

http://www.nature.com

 

University of Ottawa

http://www.uottawa.ca

 

 

 

 

 

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