Comparative susceptibility among three stocks of yellow perch, P erca flavescens ( M itchill), to viral haemorrhagic septicaemia virus strain IV b from the G reat L akes

The G reat L akes strain of viral haemorrhagic septicaemia virus IV b ( VHSV ‐ IV b) is capable of infecting a wide number of naive species and has been associated with large fish kills in the Midwestern U nited S tates since its discovery in 2005. The yellow perch, P erca flavescens ( M itchill), a freshwater species commonly found throughout inland waters of the United States and prized for its high value in sport and commercial fisheries, is a species documented in several fish kills affiliated with VHS . In the present study, differences in survival after infection with VHSV IV b were observed among juvenile fish from three yellow perch broodstocks that were originally derived from distinct wild populations, suggesting innate differences in susceptibility due to genetic variance. While all three stocks were susceptible upon waterborne exposure to VHS virus infection, fish derived from the M idwest (Lake Winnebago, WI ) showed significantly lower cumulative % survival compared with two perch stocks derived from the East Coast ( P erquimans River, NC and C hoptank River, MD ) of the U nited S tates. However, despite differences in apparent susceptibility, clinical signs did not vary between stocks and included moderate‐to‐severe haemorrhages at the pelvic and pectoral fin bases and exophthalmia. After the 28‐day challenge was complete, VHS virus was analysed in subsets of whole fish that had either survived or succumbed to the infection using both plaque assay and quantitative PCR methodologies. A direct correlation was identified between the two methods, suggesting the potential for both methods to be used to detect virus in a research setting.