Date of this Version
Numerous sturgeon species have been integral components of significant fisheries within North America. Species of sturgeon have played an important historical role in recreational and commercial fisheries of various riverine and Great Lakes communities throughout the United States. Present commercial fisheries for sturgeon species are virtually non-existent, in part due to overexploitation, coupled with an inherently long period of time for sturgeon species to become sexually mature.
Two species within the Missouri River basin (pallid sturgeon, Scaphirhynchus albus) and shovelnose sturgeon, Scaphirhynchus platorynchus) have been recently found to harbor a suspect virus (currently being referred to as the Missouri River Sturgeon Iridovirus, or MRS IV), very similar to but different from the White Sturgeon lridovirus (WSIV). Currently, MRS IV, has been detected only in captive propagated sturgeon in Service facilities and in wild shovelnose sturgeon collected in the Missouri River below Ft Peck. Both shovelnose and pallid sturgeon have been diagnosed with the iridovirus agent. In USFWS Region 6, three Service facilities have cultured sturgeon in which the iridovirus was detected: Gavins Point National Fish Hatchery, Valley City National Fish Hatchery, and Garrison Dam National Fish Hatchery.
Current information regarding the significance of the iridovirus in Missouri River sturgeon species is lacking in the following areas: a) its host and geographic range in wild populations, b) its transmissibility to other species of sturgeon and the question of vertical transmission from parents to progeny, c) the utility of existing sturgeon cell lines and primary cell cultures, and d) applicable diagnostic and monitoring procedures for both latent and patent infections.
Pallid sturgeon are Federally listed as an endangered species, not legally catch-able and subject to a multi-agency recovery effort. The current recovery plan calls for supplemental propagation programs to provide absolutely essential recruitment in the Upper Missouri River basin where natural recruitment is non-existent and has been so for over 20 years. Without releasing hatchery propagated sturgeon into the wild, to pass on the gene pool from the aging pallid sturgeon population, the species will become extinct in the upper basin. Service facilities in Region 6 have implemented culture programs and management activities to assist in the recovery effort. The intensive culture of the pallid and shovelnose sturgeon presents fish health concerns. As with most fish pathogens, the iridoviral agent can be associated with mortalities in cultured sturgeon but has not been identified as a mortality factor in the wild.
The significance of the iridoviral agent in shovelnose and pallid sturgeon is not entirely known, primarily as a function of our lack of knowledge regarding the epizootiology and life cycle of the viral agent. Management decisions relative to both species, must be based on good science with regard to pathogen detection and significance. Improved management decisions can be made if we have a good understanding of the naturally occurring presence of this virus in wild populations of both species. Lack ofthorough information is currently resulting in management decisions that err on the side of caution regarding stocking of positive or suspect sturgeon. In the not too distant future, decisions will need to be based on the need to prevent extinction of the species as the wild population continues to age toward senility and death. The Upper Basin Pallid Sturgeon Work Group identified iridovirus sampling as a priority activity for continuing pallid sturgeon recovery in the Missouri River. Our sturgeon collections and iridovirus sampling are being conducted to meet this goal.