The threshold biomass for fisheries on Pacific herring Clupea pallasi that spawn near Togiak, in Bristol Bay, Alaska, was reviewed based on the data collected in the decade following threshold harvest policy initiation in 1987. The current threshold of 31,752 mt (35,000 tons), below which fishing is precluded, was found to be too low. This threshold had been set at 25% of the spawning biomass ... [Show full abstract] during a period that included substantial harvests. A threshold set at 25% of the average unfished biomass (AUB) is widely used in other herring fisheries along the Pacific coast. A 1,000-year simulation of abundance was used to determine AUB under several possible spawner-recruit relationships and sets of stock-assessment data. Four alternative age-structured assessment (ASA) models fit to the available data for Togiak herring under different sets of assumptions were used to represent the uncertainty in the stock-assessment data. A large discrepancy between abundance trends from aerial surveys and trends apparent in age-composition data resulted in a large amount of uncertainty about past biomass levels in the ASA model, which was reflected in the AUB estimates. Ricker and empirical spawner-recruit models fit to the information from the ASA analysis were used to simulate density-dependent effects on recruitment. The uncertainty in the basic population dynamics data provoked a wide range of AUB estimates under different sets of assumptions. AUB estimates ranged from approximately 159,000 to 433,000 mt, and the resulting thresholds ranged from approxi-mately 40,000 to 108,000 mt. Based on this information, we recommend that the Togiak threshold be raised to at least 45,000 to 50,000 mt, pending further resolution of the discrepancies between abundance trends from aerial surveys and abundance trends from age compositions. Setting thresholds at 25% of AUB only rarely triggered fishery closures and these fishery closures produced very little reduction in long-term average yield.