From milk jugs to millions: How American shad took over

National Fisherman —

In early 1871, American shad was a popular food and sport fish, and the California Fish Commission engaged Seth Green, regarded as the father of fish culture in North America, to transport more than 12,000 American Shad fry by train to California

Green filled milk jugs with shad fry and took them onto a transcontinental train. After a seven-day journey, he arrived in California with 10,000 little fish still alive, and he released them into the Sacramento River near the town of Tehama.

The project turned out to be more successful than Green could have imagined. From Sacramento, shad colonized and were introduced to rivers all along the West Coast. The Columbia River now sees shad annual runs of as many as 7 million fish, and shad are now the most abundant anadromous fish in the river. They make up over 90 percent of the recorded upstream migrants in some years and raise concerns about their impact on diminished salmon runs.

“At such high abundances, shad interfere with efforts to aid salmonid upriver adult returns by obstructing efficient processing of salmon at collection facilities, lowering oxygen concentrations in fish ladders, and complicating accurate identification of migrating salmon and steelhead in fish counting facilities,” says a report published by the Northwest Power and Conservation Council. “Potential hazards of increasing shad populations to native fishes include greater competition for food and critical nursery habitat, predation on salmon young, disease transmission, or some combination of these processes.”