Jason Stolarski | Geology Reports

USGS2026

Escaping the density trap: Estuarine connectivity supports juvenile river herring growth

Alewife ( Alosa pseudoharengus ) and blueback herring ( A. aestivalis ) require connectivity among freshwater, estuarine, and marine environments to complete their life cycle. Impediments to watershed connectivity are major drivers of population declines along the eastern United States, where physical barriers and low-flow conditions can inhibit or delay juvenile outmigration, limiting access to productive estuarine nursery habitats. Because juvenile growth strongly influences early survival and recruitment, understanding how connectivity to estuaries shapes growth across nursery habitats is critical but remains poorly understood. We evaluated juvenile river herring growth across connected lake, river, and estuary habitats in three coastal Massachusetts watersheds from 2021 to 2023. Juvenile fish and water quality were sampled throughout each summer, and sagittal otoliths were used to estimate growth rates. Juvenile growth was enhanced in downstream estuarine habitats where connectivity was intact and in-lake juvenile densities were high, as observed in the Weymouth Back River watershed. In contrast, growth limitations occurred in a high-density system with restricted passage, where juveniles occupied shallow, eutrophic river reaches in the Mystic River watershed. Growth rates were similar between lake and estuarine habitats in a low-density system (Essex River watershed), indicating that estuarine benefits to growth are context dependent. Together, these results demonstrate that connectivity to estuarine habitats can alleviate density-dependent growth constraints, but that barriers and delayed outmigration to estuaries can limit these benefits. Maintaining or restoring functional freshwater–estuarine connectivity is therefore critical for sustaining juvenile production and provides a clear management priority for municipalities, state and federal agencies, and watershed managers working to restore river herring populations in fragmented coastal systems.

Massachusetts↗

USGS2021

Hydrology of annual winter water level drawdown regimes in recreational lakes of Massachusetts, United States

Annual winter water level drawdown (WD) is a common lake management strategy to maintain recreational value by controlling nuisance macrophytes and preventing ice damage to shoreline infrastructure in lakes of the northeastern United States. The state of Massachusetts provides general guidelines for lake managers to implement and practice WDs. However, WD management reporting is not required and as such empirical water level records are scarce, making it difficult to assess guideline adherence and link these management actions to littoral habitat conditions. We monitored water levels bihourly in 18 lakes with ongoing WD regimes and 3 non-drawdown lakes over 3–4 yr. Our results show an interlake drawdown magnitude gradient of 0.07–2.66 m with intralake consistency across years. Corresponding WD magnitudes generated exposure of 1.3–37.6% for entire lakebeds and 9.2–71.1% for littoral zones. WD durations averaged 171 d and ranged widely from 5 to 246 d. Longer recession and refill phase durations and faster recession rates were moderately to strongly correlated with drawdown magnitudes. WDs were predominantly initiated prior to the state of Massachusetts 1 November starting guideline (83.1%) and refilled to summer reference levels after the recommended date of 1 April (70.6%). To minimize ecological impacts while still meeting recreational goals, WD performance guidelines may require a more fine-scale approach that integrates local hydrogeomorphic features and the presence of WD-sensitive littoral biotic assemblages. However, climate change model projections of warmer and wetter winters in the Northeast indicate increasing uncertainty for WD as an effective and worthwhile macrophyte control tool.

Massachusetts↗