Acoustically Measured Distribution and Abundance of Atlantic Menhaden (Brevoortia tyrannus) in a Shallow Estuary in Long Island, NY

Abstract

Atlantic menhaden (Brevoortia tyrannus) is an euryhaline forage fish abundant along the eastern coast of the USA that seasonally migrates between the open ocean and shallow water estuaries. These fish are known for forming large, dense schools and are important prey for piscivorous fish, seabirds. Following several large fish kills in the late spring of 2015 in the western Peconic Estuary in Long Island, New York, we conducted multiple surveys during the spring, summer, and fall using scientific echosounders to quantify menhaden abundance in this region. Acoustic backscatter data were used to estimate numeric abundance and biomass of menhaden for the western Peconic Estuary. We found that the 2015 fish kills represented between 7 and 18% of the total local population (~ 2.4 million) that were present at the time. Significant changes in target strength distributions during the study suggest that the size classes of menhaden present in the estuary change as fish grow or migrate in and out of the estuary. This study demonstrates that vertical beam active acoustics is a viable method for quantifying forage fish in a very shallow (< 4 m depth) estuary.