Triangulating the Story of an Native Invader Jellyfish Using Contemporary Field Surveys, Histological Analysis, and Local Ecological Knowledge (LEK)

Historical data on "native invader" species are typically scarce because such species are often understudied until they become a problem. The sea nettle jellyfish (Chrysaora quinquecirrha) is one such native invader in Barnegat Bay, NJ. The species was noted in region in 1928, but little other relevant data are available. This study aimed to (a) determine when the sea nettles became abundant and (b) identify factors that may have contributed to that shift in abundance. We used three approaches: (1) field sampling, (2) gonad histological analysis to infer reproductive mode and (3) interviews of residents about their first encounter with sea nettles. Sea nettles were more abundant in developed creeks than in undeveloped creeks, and demonstrated limited evidence of sexual reproduction. Residents marked the sea nettle boom starting in 2003, which corresponds with the time when vinyl was replacing creosote-treated wood for dock and bulkhead construction. These results suggest that shifting from chemically treated wood to vinyl – providing a better substrate for the asexually reproducing polyp form of the sea nettle – may have contributed to the increase in sea nettles. Using local ecological knowledge (LEK) in combination with other techniques can offer historical perspective on data-poor situations.