Occurrence, Abundance, and Developmental Stage of a Parasitic Nematode in Juvenile Bluefish (Pomatomas saltatrix) Inhabiting the Hudson River Estuary, 2010

Environmental stressors such as pollution and climate change may make fishes highly vulnerable to parasitic infections through immunosuppression.  Philometra saltatrix is a parasitic nematode that is specific to bluefish (Pomatomus saltatrix). The rate of infection, life history, and effects of Philometra saltatrix in juvenile bluefish are unclear.  Our objectives were to determine the occurrence, abundance, developmental stages, and assess the pathological effects of Philometra saltatrix infection in juvenile bluefish inhabiting the Hudson River estuary, 2010.  Philometra saltatrix was found in 50% of the 81 fish examined.  Occurrence increased over time and by November, all of the juvenile bluefish processed were infected.  Abundance of Philometra saltatrix was the greatest in October (5 nematodes/infected fish).  Sub-gravid (with eggs), and gravid (with larvae) females were found in the greatest proportion, and 92% of the nematodes were located in the pericardium.  Pathological effects included severe pericardial hypertrophy, granulomatous inflammation, fibrosis, and visceral adhesions.  The occurrence of Philometra saltatrix in juvenile bluefish observed in this study is among the highest reported for philometrids.  We provide the first account of reproducing Philometra saltatrix in the pericardium of juvenile bluefish, and the pathologies we observed could be severe enough to cause mortality in affected fish.