The window at Bonneville Dam looks like a submerged hallway.<\/p>\n
Water the color of old glass presses against the concrete.<\/p>\n
Something silver keeps flashing past, faster than anyone can count by eye.<\/p>\n
For decades the fish ladder<\/strong> here was built with one animal in mind.<\/p>\n It was not the one that showed up.<\/p>\n So what is actually climbing those steps today, and why does it keep winning?<\/p>\n Bonneville’s passage system was designed around Pacific salmon and steelhead, the fish that gave the Columbia River its fame and its canneries. American shad are herring family fish from the Atlantic coast, and they spawn in warm, slow water rather than cold gravel headwaters. The dammed mainstem handed them exactly that, trading a fast channel for long reaches of slackwater<\/strong>.<\/p>\n Their spring timing<\/strong> helps as well. Shad push upriver as the water warms and the flow drops, which is when concrete steps are easiest to climb. Nobody poured that concrete with shad in mind.<\/p>\n Shad numbers above Bonneville stayed modest until an upstream dam drowned Celilo Falls, a rapids that had limited how far inland they could push. Regional science reviewers describe the flooding of the falls as apparently facilitating that upstream access<\/strong>, which is a reading of the record rather than a demonstrated cause. Federal scientists also credit successful passage at the dams, good spawning and rearing habitat, and low harvest by commercial and sport fishers.<\/p>\n Picture the viewing glass at the peak of the run. Instead of a scattering of large, dark salmon shapes, the window fills with a dense moving curtain<\/strong> of smaller, brighter fish, shoulder to shoulder, all pushing the same direction at once.<\/p>\n Run timing at Bonneville extends from mid May through early August, with peak daily counts occurring in June. At the height of it the tally stops looking like wildlife monitoring and starts looking like traffic: a single day at the ladder has produced 233,899 shad<\/strong>.<\/p>\n The salmon the structure was built for are still there, still counted, still the reason the windows exist. They are simply no longer the crowd. In some recent years shad have made up more than 90 percent<\/strong> of the recorded upstream migrants at the dam.<\/p>\n American shad were planted in the Sacramento, Columbia and Willamette rivers repeatedly beginning in 1871 by the<\/strong> US Fish Commission. Before 1960, fewer than 20,000 adults a year were estimated at Bonneville Dam. Their numbers rose above a million a year after The Dalles Dam<\/strong> was completed and flooded Celilo Falls.<\/p>\n The comparison with salmon is where the scale lands. In 2019, more than seven million shad passed above Bonneville Dam by late August, compared with fewer than 250,000 adult wild anadromous salmon and steelhead and 450,000 hatchery salmonids, according to a review by the region’s Independent Scientific Advisory Board<\/a>. Across an earlier baseline period, the average Bonneville count was 2,225,797 shad against 939,242 salmonids, about 70 percent shad<\/strong>.<\/p>\n Even those figures undercount the fish. The US Geological Survey has estimated that 10 million to 20 million adult shad may enter the Columbia annually, and the dam count reflects only part of a run that also spawns below Bonneville.<\/p>\n This is not universal good news for fish passage, and that complication matters. On East Coast rivers where shad are native, comparable infrastructure barely works. One study metric was the share of fish passing the first dam that also passed the second, and for shad the figures were 16 percent on the Merrimack, 4 percent on the Connecticut and 32 percent on the Susquehanna, as the lead author summarized in Yale Environment 360<\/a>. Fewer than 3 percent reached<\/strong> their historical spawning reaches past all the dams.<\/p>\n Different animals also read the same concrete differently. At Bonneville, lamprey are tracked both at the fish counting windows and through separate passage systems<\/strong> at Bradford Island, Washington Shore and Cascades Island, with the two counts kept mutually exclusive. That split echoes what happens where young river herring swam through a reshaped turbine<\/a> on a much smaller Maine dam.<\/p>\n Biologists are still working out how much shad actually cost salmon. Published reviews lay out the possible ecological interactions between salmon and American shad across their life histories and habitats without closing the question, and the growth of the shad population is itself seen as a strain on the infrastructure<\/strong> built to recover salmonids.<\/p>\n The ladder keeps counting both species daily, which at least keeps the question answerable rather than guessed at. Other hydropower passages built for one species are now being measured the same way, species by species, much like the eels that passed through a compact canal turbine<\/a> without a single loss.<\/p>\n The lesson from that viewing window is less about one fish replacing another and more about how little control engineers have over who uses what they build. A structure raised for one migration became the stage for a completely different one<\/strong>, and the glass still fills every spring with proof of it.<\/p>\n","protected":false},"excerpt":{"rendered":" The window at Bonneville Dam looks like a submerged hallway. Water the color of old glass presses against the concrete. Something silver keeps flashing past, faster than anyone can count by eye. For decades the fish ladder here was built with one animal in mind. It was not the one that showed up. So what … Read more<\/a><\/p>\n","protected":false},"author":28,"featured_media":45061,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"rank_math_focus_keyword":"columbia river dam","rank_math_title":"A Columbia River dam ladder fills with 7 million shad some springs, far outnumbering the salmon and steelhead the concrete was poured to carry","rank_math_description":"At Bonneville Dam, millions of Atlantic origin shad now dwarf the salmon and steelhead runs the fish ladder was built to carry each spring.","footnotes":""},"categories":[8],"tags":[],"class_list":["post-45043","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-energy"],"_links":{"self":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/45043","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/users\/28"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/comments?post=45043"}],"version-history":[{"count":2,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/45043\/revisions"}],"predecessor-version":[{"id":45106,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/45043\/revisions\/45106"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/media\/45061"}],"wp:attachment":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/media?parent=45043"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/categories?post=45043"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/tags?post=45043"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Why a fish from the wrong ocean owns the climb<\/h2>\n
The spring run turns the window into a wall of silver for ten weeks<\/h2>\n
Counts climbed from under 20,000 a year to more than 7 million<\/h2>\n
Other rivers show the opposite problem with the same ladders<\/h2>\n
What the mismatch still leaves unanswered<\/h2>\n