Using Otolith Geochemistry to Quantify the Duration of Estuarine Residency of Rainbow Smelt in New Hampshire.

Cacacie, Alexa*¹, Chloe Pearson², Nathan Miller³, Benjamin Walther⁴, Nathan Furey², John A. Mohan¹, ¹University of New England, Biddeford, ME, ²University of New Hampshire, Durham, NH, ³The University of Texas, Austin, TX, ⁴Texas A&M University, Corpus Christi, TX

Successful management of diadromous fish species relies on knowledge of seasonal migration patterns. Although acoustic telemetry can be used to study freshwater, estuarine, and marine movements in diadromous fishes, the technology is limited by animal body size and battery duration. Elemental analysis of chronological growth layers in otoliths provide continuous life history records. Specifically, the concentrations of strontium and barium record movement throughout estuarine salinity and temperature gradients. Rainbow smelt (Osmerus mordax) are an important diadromous fish that contribute to popular recreational ice fisheries throughout New England. However, due to human activity, migratory populations of rainbow smelt have declined considerably in recent decades and are now listed at state and federal levels as species of concern. Given the importance of rainbow smelt to recreational ice fisheries in New England, and their role as primary prey for larger predators, the goal of this study was to determine time partitioned between freshwater, estuarine, and marine waters throughout Great Bay, NH and four of its tributaries. To do so, we used LA-ICP-MS analysis to quantify strontium and barium concentrations from otolith core to edge in adult rainbow smelt (n = 79; TL=149 mm - 232 mm) to determine residency and movement from bodies of water with varying salinities. We compared these results to previous studies relating water chemistry and trace element uptake in teleost fish to better understand residency in NH estuaries. This study increases our understanding of estuarine use by rainbow smelt by identifying important habitats, quantifying duration of residency, and characterizing connectivity among freshwater, estuarine, and marine systems to optimize current management efforts.