Assessing the Stability of Maine River Herring Runs and the Effect of Restoration Efforts through Comparison of Population Metrics

Although site-specific counts of adult spawning river herring can provide information about population growth or decline, this method alone is not reflective of overall stability of a specific run. We used biological information from over 30 runs in Maine to develop a comparative multivariate model to assess site-specific run stability. Recently re-established runs were closely related to runs with long-term passage problems that have been sustained by stocking. These runs were dominated by age-3 and age-4 fish and had low repeat spawning rates, indicating that either the run had not been established for a long enough period of time to perpetuate itself, or that fish were only successfully spawning in one year and possibly not surviving adult downstream migration. Conversely, runs with few passage problems were characterized by wider age distributions and a higher degree of repeat spawning. This latter group was composed of both harvested and un-harvested runs. The majority of harvested runs grouped separately from the two previous, where a somewhat truncated age distribution was evident and moderate repeat spawning occurred. Collecting biological data over time will allow us to track how restoration efforts or changes in management can lead to a run being reassigned within the model.