Epizootic mortality in the pilchard Sardinops sagax neopilchardus in Australia and New Zealand in 1995. I. Pathology and epizootiology

Abstract

A large-scale eplzootic occurred In the Austialas~an pllchard S a r d~n o p s sagax neop~l c h a r d u s between March and September 1995 ovei more than 5000 km of the Australian coastline and 500 km of the New Zealand coastline Affected fish died wlthln a tew mlnutes of cl~nical slgns of respiratory distress and death was associated wlth hypoxaemla a n d hypercapnea Significant leslons were confined to the gllls and comprised acute to subacute inflammation followed by blzal re epithelia1 hypertrophy and hyperplasia The lesions were initially focal but progressed to become generalised over about 4 d Pathological changes in atfeded fish from xvestern Australia eastern Australia a n d New Zealand were simila~, suggesting a common aetiology The lesions were unllke those associated w~t h ichthyotoxic algae, s~l~c e o u s algae, phys~cochemical factors fungi, bacterla dinoflagellates, amoebde, other protozoa and inetazoa A herpesvlrus was consistently present In gills of affected flsh and absent from unaffected pilchards and IS proposed as the aetiological agent T h e late of spread of the mortal~ty front (approulmately 30 km d ' ) In relation to the migration late of pilchaids a n d plevaillng currents suggests that a vector was involved The dlsease may have been newly introduced lnto Australian wateis KEY WORDS Clupeoldel . Pllchard . Sardinops sagax neopilchardus . Gill dlseases . Pathology .

Dynamics of viral hemorrhagic septicemia, viral erythrocytic necrosis and ichthyophoniasis in confined juvenile Pacific herring Clupea pallasii

“…Dis Aquat Org 70: [201][202][203][204][205][206][207][208] 2006 Sardinops sagax biomass from 165 000 to 37 000 tonnes in 1995 and from 147 000 to 36 000 tonnes in 1998 (Jones et al 1997, Whittington et al 1997, Gaughan et al. 2000, Ward et al 2001.…”

“…2000, Ward et al 2001. Although mortality was associated with herpesvirus-like particles in the gills of affected sardines (Hyatt et al 1997, Jones et al 1997, Gaughan et al 2000, transmission studies and attempts to fulfill Koch's postulates were unsuccessful (Bernoth 2002).In Puget Sound, Washington (USA), several pathogenic agents, including viral hemorrhagic septicemia virus (Hershberger et al 1999, Kocan et al 2001, erythrocytic necrosis virus (MacMillan & Mulcahy 1979) and Ichthyophonus hoferi (Kocan et al 1999, Hershberger et al 2002 are enzootic in populations of Pacific herring Clupea pallasii. Viral hemorrhagic septicemia virus (VHSV) is grouped with several other commercially and ecologically important fish viruses in the Novirhabdovirus genus of the family Rhabdoviridae (Walker et al 2000).…”

Using climate downscaling to hypothesise impacts on apex predator marine ecosystem dynamics

“…Besides regional variability, pilchards could also be subjected to decadal regimes (e.g. as for Pacific sardines Sardinops sagax; Chavez et al 2003), which in combination with a 1995 pilchard mass mortality event in New Zealand (Whittington et al 1997) could explain declining pilchard populations.…”

Infectious Diseases in Wildlife

“…The lack of a history of large-scale pilchard mortality in Australia, the focal origin of the outbreak and the rapid spread of disease over large areas suggest a recently introduced pathogen. Whittington et al (1997) proposed two potential mechanisms of introduction: ballast water discharge by ocean-going ships or the importation of over 10 000 tonnes per annum of non-quarantined frozen mixed bycatch species into Australian waters from North and South America and Japan for use in the bluefin tuna farming industry. In 1998 a similar epizootic occurred, the origin and epizootiology of which resembled that of the 1995 outbreak.…”