Research challenges conventional notions about salmo...(th that records a passing vehicle equipp...)

The team found that the two species of juvenile salmon migrating through the Columbia Rivers eight dams survived the freshwater and early marine portions of their journey to the ocean as well as those in the un-dammed Fraser River, challenging widely-held notions about factors affecting salmon abundance. In fact, more survived in the dammed river journey once distance or travel time was taken into account and survival was greater during migration within the hydropower system than below the dammed section.

An animation illustrating the migrations is online at: www.postcoml.org/page.php?section=community&page=PLoSembargo

The cornerstone of this study lies in its new method of tagging the salmon, which although larger than previously existing hardware is much more versatile. These new tags no not require the tagged fish to be funnelled towards a short range detector, but instead can be monitored using a series of listening arrays maintained as part of the Pacific Ocean Shelf Tracking Project, which is based at the Vancouver Aquarium. These listening arrays allow measurements to be taken not only in controlled, dammed rivers but also in free-Flowing flowing rivers and even in the coastal ocean, a great step forward.

This study, as well as the technology it introduces, has imminent applications to the study of other species, such as herring, halibut and cod, to explore their behaviour and survival. It also opens up a wider debate about the factors that influence salmon survival, especially regarding human intervention and adaptation of rivers.

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