Acoustic quantification of abundance, biomass, and size class of Atlantic menhaden (Brevoortia tyrannus) in a shallow estuary in Long Island, New York

Abstract

Atlantic menhaden (Brevoortia tyrannus) is an euryhaline forage fish commonly found on Long Island from late spring to fall and is both ecologically and economically important to fisheries along the entire eastern coast of the United States. Schools of menhaden frequently occupy the shallow (<4 m) bays and rivers of the western Peconic Estuary on Long Island, New York. These shallow habitats are difficult to sample using traditional pelagic (i.e., net trawls) or shore-adjacent (i.e., beach seines) methods due to shallow water depths and salt marsh coastline. We conducted multiple acoustic surveys using fisheries echosounders (38, 120, and 200 kHz) and sidescan sonar between May and November in 2015 and 2016 in Flanders Bay and the Peconic River. Active acoustic surveys were capable of providing estimates of abundance, biomass, and length distribution of Atlantic menhaden. Abundance and biomass estimates for the entire western Peconic Estuary were extrapolated from survey data and showed large (order of magnitude) variations in the menhaden population in these waters from spring to fall. Length distributions of menhaden differed both among seasons and between years. Data were ground-truthed using video, photographs, and morphological measurements of Atlantic menhaden.