Assessment of clinging jellyfish Gonionemus vertens populations in New Jersey 2016 - 2020



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Trenton, N.J. : New Jersey Department of Environmental Protection


Gonionemus vertens (Clinging Jellyfish) is a species of small hydrozoan native to the Pacific Ocean. In 2016, it appeared in New Jersey with the first individual being documented from the Manasquan Canal and subsequent individuals collected in the Shrewsbury River Estuary. Research regarding the distribution of G. vertens was conducted during the summers of 2016 and 2017 in northern Barnegat Bay, the Manasquan River, and the Shrewsbury River Estuary. While the first individual G. vertens confirmed was from the Manasquan Inlet, no other individuals were ever collected from this region nor in the northern reaches of Barnegat Bay. All individuals, including recruiting polyps, were identified from the Shrewsbury River Estuary (54 individual G. vertens medusae were collected in 2016 and 218 collected in 2017). In both years, individual polyps were collected on JADs (Jellyfish Attracting Devices), but no large-scale larval recruitment of polyps was observed, as only one single individual polyp was on a JAD during 2016 and 2017. Subsequent laboratory observations of polyp development from larvae suggest it often takes 3 to 4 months for polyps to fully develop, so it is probable that the polyps from the field JADs likely had merely climbed onto the JAD surface and were not actively recruiting there. It is clear that a well-defined population exists in the Shrewsbury River and continued blooms in the late spring and early summer are expected in the future. Since no other individuals were collected in the Manasquan and Barnegat Bay estuaries after the first individual was observed, it is unclear as to whether that observation was anomalous or whether another population remains in this area, but is not actively blooming. During surveys of the Manasquan River a large, viable eelgrass (Zostera marina) bed was identified near the original collection site of the first G. vertens, so the preferred habitat for G. vertens is present, however the abundant populations in the Shrewsbury River are using macroalgae as habitat, so both algae and seagrass are viable habitat for G. vertens.



New Jersey, Jellyfishes - New Jersey, Gonionemus vertens