Understanding Spawning Behavior and Habitat Use By Anadromous Rainbow Smelt (Osmerus mordax) Using Passive Integrated Transponder Systems and Telemetry

Anadromous rainbow smelt spawn in coastal streams and rivers and provide an important prey base to many marine predators.  Populations range-wide have experienced decline possibly due to habitat degradation and loss of habitat.  This study quantified within-season repeat spawning behavior at two sites in the Gulf of Maine, and described movements during and following the spawning season in the Great Bay and Piscataqua estuary complex, NH. Repeat spawning behavior was found to be a predominantly male behavior. The average rate of repeat spawning by males was consistent among study years and study sites. This result is important when considering the relationship between sex ratios and catch-per-unit effort (CPUE): at survey sites where sex ratios were highly skewed CPUE values were comparatively low, while sex ratios were more even at sites with higher CPUE values. Skewed sex ratios can indicate that the number of spawning females is limited, which can lead to population decline. Thus, comparing sex ratios among sites can be one tool to identify stressed populations. Regarding larger scale movements, smelt of both genders visited the mouth of multiple rivers within an embayment during the spawning season and made use of a tidal estuary system after spawning activity ceased.