Bonneville Dam Fish Counts, Explained: Reading the Run Like a Pro

Every serious Columbia basin angler eventually becomes a fish-count reader. The daily numbers from Bonneville Dam are the closest thing the Northwest has to a stock ticker for salmon — obsessively checked, endlessly argued over, and genuinely useful once you know what they do and don’t say.

This is how the counts work, what the numbers mean, and the handful of reading habits that separate anglers who use counts well from anglers who just look at them.

What’s actually being counted

Bonneville is the first dam on the Columbia, about 145 river miles from the ocean. Every salmon, steelhead, shad, and lamprey headed for the thousand-plus miles of river and tributary upstream has to climb its fish ladders — and partway up each ladder is a counting window. Trained counters at the windows (with video filling the gaps) identify and tally fish by species: Chinook, coho, sockeye, steelhead (clipped and unclipped), chum, shad, lamprey.

Those tallies are compiled and published daily by the Army Corps of Engineers, and re-served with history and averages by sites like Columbia Basin Research’s DART. The result is something almost no fishery anywhere has: a daily, species-level census of a river’s entire upstream migration, going back decades.

Two boundaries on what the number means:

• It counts ladder passage, not river population. Fish milling in the estuary, holding below the dam, or turning into lower-river tributaries never cross a window.
• It’s a rate, not a total. A single day’s count tells you how many fish moved that day — which is exactly why it’s useful for timing, and exactly why one day proves nothing.

The calendar inside the counts

The Columbia’s runs overlap all year, and managers split them by date at Bonneville. The working calendar every count-reader carries:

• Spring Chinook — counted through mid-June. The famous early run, headed far upriver.
• Summer Chinook — mid-June through July.
• Fall Chinook — August into November, the biggest Chinook numbers of the year and the engine of the Buoy 10 fishery.
• Coho — late August through fall.
• Sockeye — a sharp June–July pulse.
• Steelhead — a long summer-into-fall migration with fish for upriver tributaries.
• Shad — millions in June; not why you’re reading the counts, but they dwarf everything else on the graph while they run.

Knowing the date windows matters because the same raw number reads completely differently by season — and because the transition weeks (is this late-summer Chinook or early fall fish?) are where count-watching gets genuinely predictive.

How to read the numbers like a pro

1. Always read against the 10-year average for the date. A daily count in isolation is noise. The question is never “is 8,000 a big number?” — it’s “what does this date usually do?” Above the date-average and climbing is a building run; below it and flat is a late or weak one. DART publishes the averages next to the dailies for exactly this reason.

2. Watch three to five days, not one. Single days swing on water temperature, flow, turbidity, and plain chance. A trend of consecutive building days is signal; a Tuesday spike is not.

3. Respect the lag — it points downstream-to-up. Fish are in the estuary days before they’re in the ladder, and above the dam they keep moving for days after. So the counts serve two different anglers two different ways: if you fish Buoy 10 and the lower river, big counts are confirmation — those fish passed you recently, and the run they belong to is real. If you fish above Bonneville — the gorge, Hanford Reach, the Snake, the upper Columbia — counts are advance notice: today’s ladder is your water’s next arrivals.

4. Let conditions explain the weird days. Migration slows when the river runs hot, high, or dirty, and fish that stalled move in pulses when conditions ease. A dead count during a heat spike followed by a huge day isn’t a mystery — it’s a queue emptying. Reading counts alongside flow and temperature is what makes the picture make sense, which is why having the gauge data next to the count matters.

5. Plan on the build, not the peak. By the time a run’s peak day is obvious in the record, it’s behind you. The trips that hit it right get planned when the counts start outrunning their date-average — that’s the run announcing itself.

Where to watch

The Army Corps publishes the official dailies, and DART layers on history, averages, and graphs. Baseline Maps surfaces the Bonneville counts in the app alongside the river’s live flow and temperature — the three numbers that read the run — so the check that used to be three browser tabs is one glance. However you watch them, watch them the same way: against the average, over several days, with the lag in mind.

The counts won’t tell you where to anchor or what to run. What they’ll tell you — earlier and more honestly than any report — is whether the fish have shown up. In a fishery where the most expensive mistake is burning a weekend on a run that hasn’t arrived, that’s the number worth reading right.