Non-native shad bring ocean nutrients into Columbia system

Non-native shad were introduced in the Columbia River more than a century ago and have prospered, with recent annual runs in the vicinity of 2 million. To a limited extent, they help fill the role huge salmon runs once did of bringing important trace elements from the ocean into upstream areas.

COLUMBIA RIVER — A non-native anadromous — or ocean-going — fish now provides as much marine-derived nutrients, such as phosphorus and nitrogen, in the Lower Columbia River as do native salmon.

While the numbers of salmon and steelhead have declined over the past century, the number of American shad has risen significantly, particularly after the construction of The Dalles Dam, which removed a barrier — Celilo Falls — to the shad’s upriver migration.

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