Assessing Round Goby invasion risk in the Hudson River estuary and adjacent coastal waters

ABSTRACT Objective The invasive Round Goby Neogobius melanostomus has spread rapidly since its introduction into the Great Lakes during the 1990s, reaching the Hudson River estuary, New York, in summer 2021. To address the potential for further coastward expansion of this species, we modeled the risk of continued southward expansion of Round Gobies in the Hudson River estuary and the risk of invasion into the adjacent brackish and coastal waters. Methods We modeled the predicted survival rate of Round Gobies across salinity and temperature combinations using mortality estimates from controlled laboratory experiments that assessed the salinity tolerance of specimens, taken from freshwater, at temperatures reflective of seasonal conditions found in the Hudson River estuary. Using historic data sets of benthic temperature and salinity layers as inputs, we then mapped the predicted Round Goby monthly survival across four seasons throughout the Hudson River estuary, New York Harbor, and Long Island Sound waters to serve as an indicator of range expansion risk. Results We found the entirety of the Hudson River estuary to be at high risk (≥90% monthly survival) of Round Goby expansion year-round. Lower portions of New York Harbor and eastern portions of Long Island Sound had low invasion risk in summer and fall conditions (20% monthly survival); however, in cooler winter and spring conditions, monthly survival probability exceeded 90% throughout most of the study area, including higher-salinity coastal waters found in Long Island Sound. Conclusions Our risk maps provide insights to inform surveillance efforts and set expectations about the potential for continued expansion of Round Gobies at this North American coastal invasion front.