Decadal-scale changes in fish spawning strategies: A case study of striped bass in the Hudson River

• We developed three novel indices to evaluate the spawning behavior of striped bass. • The striped bass showed three different spawning strategies from 1975 to 2014. • A narrower range of optimal spawning temperatures was found. • Reduced diversity in spatial and temporal spawning behavior was found. Understanding spawning behavior is critical in evaluating the productivity and vulnerability of fish populations to exploitation and climate change. Using the ichthyoplankton data collected in the Hudson River Biological Monitoring Program (HRBMP), we evaluated the spawning behavior of striped bass ( Morone saxatilis ) in the Hudson River estuary (HRE). We developed three novel spawning optimum indices: Thermal Optimum Index (THOI), Temporal Optimum Index (TEOI), and Spatial Optimum Index (SOI). Our results showed that striped bass prefer to spawn at certain temperature ranges during two specific and distinct time periods but in extensive locations in the HRE. Their spawning behavior had changed over time, with two shifts occurring in 1985 and 1998 and resulting in three distinct periods with different spawning strategies. These changes, including narrower range of optimal spawning temperatures and reduced diversity in spatial and temporal spawning behavior, may negatively impact the population’s stability and reproductive resilience. Our study demonstrates the importance of a long-term monitoring program to understand spawning strategies in striped bass and highlights the importance of considering spawning behavior in fisheries management.