How many Chinook will pass Bonneville Dam by October 31?

Currently, the prevailing sentiment in this market suggests a very high probability of over 550,000 Chinook passing Bonneville Dam by the end of October. This contrasts with some initial analyst forecasts, which predicted a more conservative count due to earlier concerns about river conditions and fish migration patterns. However, recent reports indicate a stronger-than-expected return, and this market has quickly adjusted to reflect that information. It’s important to note that prediction markets often incorporate a wider range of data and perspectives than traditional forecasts, leading to potentially more accurate predictions.

On Polymarket, this market is priced through a continuous auction mechanism where traders buy and sell shares representing their belief about the final Chinook count. The price of these shares directly reflects the market’s collective probability assessment. On Polymarket, prices reflect that venue's order book, liquidity, and how traders price the outcome right now. The current price indicates a strong conviction that the number of Chinook will exceed the thresholds offered in the market. The higher the price, the greater the market’s confidence in that outcome. This dynamic pricing ensures that the market efficiently aggregates information from all participants.

This market resolves around Nov 4, 2026, with the outcome confirmed once the official Chinook count for the season is verifiable from credible public reporting. The final count will be sourced from the U.S. Army Corps of Engineers, which monitors fish passage at Bonneville Dam. The market will settle based on the total number of adult Chinook salmon that have passed the dam by October 31, as reported by this official source. Traders should monitor these reports as the resolution date approaches to understand the likely outcome of this market.

Several factors could influence the price of this market leading up to Nov 4, 2026. Unexpected changes in river flow, water temperature, or the discovery of significant fish mortality events could all shift predictions. Reports on the health and abundance of Chinook populations in other parts of the Columbia River basin could also impact the market. Additionally, any revisions to the initial forecasts from fisheries agencies would likely be reflected in trading activity. Monitoring these developments will be crucial for anyone looking to trade in this market.