Prince William Sound Herring Program, fiscal year 2024

Pacific herring (Clupea pallasii) were collected from three sites in Prince William Sound (PWS), Alaska (Table 1) during the spring pre-spawn period from March 29 – April 1, 2024, to test for viral hemorrhagic septicemia virus (VHSV), viral erythrocytic necrosis (VEN), and Ichthyophonus prevalence (Table 1). Ichthyophonus was detected in 33% (59/180) of heart cultures from all sites combined. An inverted pattern of decreasing Ichthyophonus infection prevalence with size started around 2019 and continued through 2024 (Fig. 1). VHSV was isolated from one fish collected in Canoe Pass. The isolation was at a very low titer and was detectable only after blind passage. Neutralizing antibodies to VHSV were detected in 4.4% (14/318) of PWS herring in 2024 (Fig. 2). Erythrocytic inclusions indicative of VEN were not detected in any PWS herring (n =180) from 2024, but bacterial rods were noted in the blood films from three fish.