As record numbers of shad continue to migrate up the Snake and Columbia rivers, the Northwest Power and Conservation Council decided it’s time to look into the ecological impacts of having millions of additional fish in the Columbia Basin.

Since early May, more than 7.4 million have ­traveled past Bonneville Dam, and they’re still coming. So far, more than 3 million have continued past three more Columbia River dams to cross McNary Dam, and more than 526,000 of them journeyed up the Snake River to cross Ice Harbor Dam.

“That’s a lot of fish,” Tony Grover, NWPCC’s director of fish and wildlife, told the Council’s Fish and Wildlife Committee on Aug. 13. So many that fish counters have had trouble seeing past all the shad on the fish ladders to count the much sparser sockeye, he noted.

Grover said he went to Bonneville Dam, where some 200 people stood shoulder to shoulder catching shad from the shoreline. For anglers who enjoy them, it’s been a boon. But is there an environmental cost?

American shad were introduced to the Pacific ­Northwest in the late 1800s, and for the last 30 years their annual returns past Bonneville have ranged from 1 million to 6 million. Last year, 6.1 million shad were counted at Bonneville Dam, beating all previous records—until now. The returns to Bonneville are just a fraction of what the U.S. Geological Survey believes may enter the ­Columbia River each year.

Earlier this summer, Washington Department of Fish and Wildlife officials told Clearing Up they know of no detrimental impacts, and noted they bring with them marine nutrients that the river system may be lacking due to low returns of other anadromous fish (CU No. 1908 [12]).

Grover said he assigned Patty O’Toole, the Council’s manager of program performance and development, to research what’s known about American shad and their impacts to the larger ecosystem.

“This is very much in the early thinking stages,” O’Toole told the Council’s Regional Coordination Forum Aug. 12. She said she is gathering and reviewing ­scientific literature and will be looking into work done by the U.S. Geological Survey.

She said she welcomes any information from others. The main purpose, she said, is to find out “what are the likely impacts of this shad population that seems to be growing and growing and growing.”

K.C. Mehaffey covers fish issues for Clearing Up, and is editor of the NW Fishletter. She joined the NewsData writing team in February 2018. From lawsuits to scientific studies, she is enjoying the deep dive into the Columbia Basin's many fish topics.