In Chapter 13 on Instream Rights and Pacific Salmon, we saw how lingering adherence to the “replacement assumption” has resulted in a reoccurring tendency of the Pacific Salmon Commission to issue inaccurate abundance forecasts. That is, notwithstanding the scientific consensus that salmon hatcheries are contributing to the decline of salmon stocks, the Pacific Salmon Commission has continued to look to the volume of hatchery releases as a predictor of salmon abundance. And in Chapter 14, on Instream Rights and Fish Hatcheries, we saw how there are now proposals to apply the “replacement assumption” to delta smelt stocks despite scientific consensus that supplementation with hatchery fish is likely to damage rather than restore wild delta smelt stocks.

The reasons for this disconnect in abundance forecasting with salmon can most likely be explained by the influence of those whose economic self-interest is most at risk by acknowledging the replacement assumption is incorrect – those who rely on hydropower and diverted water from the onstream dams located upriver of the salmon hatcheries, and those employed by the salmon hatcheries. An admission that the restoration of salmon stocks requires more fish passage and instream flows, rather than more hatcheries, would challenge existing policies regarding dams, high levels of out-of-stream diversions, and hatchery operations.