Predicting Pacific Herring Spawn Events in the Howe Sound, British Columbia

Pacific herring (Clupea pallasii) are a vital forage fish, supporting marine food webs and coastal fisheries while holding deep cultural significance for Indigenous communities. The timing of Pacific herring spawning is influenced by various environmental factors, yet the specific cues driving this behavior remain unclear. This study investigates the role of lunar cycles, sea surface temperature, and photoperiod in determining the timing of Pacific herring spawning events in the Howe Sound, British Columbia. Using data collected from 2021 to 2024 by the Marine Stewardship Initiative, alongside satellite-derived sea surface temperature and the environmental variables lunar phase and photoperiod, the study examines correlations between these factors and observed Pacific herring spawning events. The findings reveal that lunar cycles, particularly the Waxing Crescent phase, are the primary driver of spawn timing, with spawning events peaking during this phase. Sea surface temperature and photoperiod showed no significant correlation with spawn timing, suggesting that tidal conditions rather than temperature or light levels are more critical for herring reproduction in this region. These results have important implications for conservation efforts, indicating that spatial protections and management strategies should be aligned with lunar cycles to maximize spawning success. This study contributes to the understanding of environmental cues influencing herring spawning and highlights the need for further research into site-specific factors and additional environmental drivers.