Reoviruses (family Reoviridae) infect vertebrate and invertebrate hosts with clinical effects ranging from inapparent to lethal. Here, we describe the discovery and characterization of Largemouth bass reovirus (LMBRV), found during investigation of a mortality event in wild largemouth bass (Micropterus salmoides) in 2015 in WI, USA. LMBRV has spherical virions of approximately 80 nm diameter containing 10 segments of linear dsRNA, aligning it with members of the genus Orthoreovirus, which infect mammals and birds, rather than members of the genus Aquareovirus, which contain 11 segments and infect teleost fishes. LMBRV is only between 24 % and 68 % similar at the amino acid level to its closest relative, Piscine reovirus (PRV), the putative cause of heart and skeletal muscle inflammation of farmed salmon. LMBRV expands the known diversity and host range of its lineage, which suggests that an undiscovered diversity of related pathogenic reoviruses may exist in wild fishes.

Northern pike (pike) Esox lucius Linnaeus are broadly distributed across Wisconsin and provide an important sport fishery for anglers. Historical management has included use of angling regulations, stocking, and protection of critical habitat areas. Pike management is often a lower priority in comparison to more intensively managed species such as muskellunge Esox masquinongy Mitchell and walleye Sander vitreous. Pike provide angling opportunities year around, with higher catch rates and live release during open water, and higher harvest rates during winter. While length of pike caught during the two seasons is generally similar, there is some evidence that larger fish are caught during winter months. Results from minimum length limit changes implemented in 1995 have been equivocal and warrant further monitoring using standardized protocol to better determine effects on populations. If natural recruitment is not limited, pike populations can reach high densities and stunting can result. Loss of nearshore habitat has continued at an increased rate as more lake homes are built and shorelines graded, and altered with riprap, sand blankets, or sea walls. If natural recruitment is lacking, fry or fingerling stocking sustains or rehabilitates populations. Most pike stocking occurs in the southeastern portion of the state where habitat loss has been extensive. Stocking in other areas is largely to re-establish populations following a chemical reclamation or from winterkill. Future management needs to establish sampling protocols to ensure comparable data on both a temporal and a spatial scale. Long-term monitoring with these methods is essential to help determine effects of various factors (e.g., regulations, habitat loss) on populations.

Sex differentiation in teleost fish is complex and often dictated by genetics, environmental conditions, and population density during critical embryonic/larval development periods. Walleye Sander vitreus have a long propagation and stocking history, and sex ratios of hatchery‐reared Walleye have been variable, typically skewed towards males, and potentially influenced by temperature. In contrast to previous fry and small fingerling Walleye stocking in Wisconsin water bodies, the Wisconsin Walleye Initiative of 2013 focused on the production of extended growth Walleye fingerlings (EGW) stocked out in fall under the assumption of greater survivorship and in response to observed declines in Walleye natural recruitment. Observed sex ratios of adult Walleye in a stocked northern Wisconsin lake chain were suggestive of EGW sex ratios skewed towards females. This lake chain has been under rehabilitation and an aggressive EGW stocking regime due to prolonged Walleye natural recruitment failures. To test whether imbalances in EGW were occurring, we collected 30 EGW from one Wisconsin hatchery in 2019 and about 50 EGW from each of three Wisconsin hatcheries in 2020 to histologically determine sex ratios. In 2019, EGW were about 97% female. In 2020, the percentage of females in hatchery samples ranged from 60% to 100%. Nonfemales in 2019 and 2020 were all undifferentiated. Our results suggest that EGW raised in Wisconsin under similar incubation and rearing protocols may be skewed towards females. If sex ratios of EGW are skewed towards females, the use of EGW may hinder efforts to rehabilitate natural recruitment. A deductive experimental and observational framework will be used to test for mechanism(s) influencing the high percentage of females in the hatchery product to inform protocols to better balance sex ratios.

Serological assays were conducted for anti‐viral hemorrhagic septicemia virus (VHSV) antibodies in four species of fish in Wisconsin (Bluegill Lepomis macrochirus, Brown Trout Salmo trutta, Northern Pike Esox lucius, and Walleye Sander vitreus) to examine spatial and temporal distributions of exposure. Sera were tested for non‐neutralizing anti‐nucleocapsid antibodies to VHSV by blocking enzyme‐linked immunosorbent assay (ELISA). Results (percent inhibition [%I]) were analyzed for differences among species, across geographic distance, and among water management units. Positive fish occurred in 37 of 46 inland water bodies tested, including in water bodies far from reported outbreak events. Using highly conservative species‐specific thresholds (mean %I of presumptive uninfected fish + 2 SDs), 4.3% of Bluegill, 13.4% of Brown Trout, 19.3% of Northern Pike, and 18.3% of Walleye tested positive for VHSV antibodies by ELISA. Spatial patterns of seropositivity and changes in %I between sampling years were also analyzed. These analyses explore how serology might be used to understand VHSV distribution and dynamics and ultimately to inform fisheries management.