Laterally compressed panfishes are small and have limited intraperitoneal space; thus, they may suffer adversely from surgically implanted transmitters even if the transmitter meets the generally recommended ratio of transmitter weight to fish weight of 2%. We studied the effects of intraperitoneal transmitters (2.81 g) on survival, growth, healing, and health of bluegills Lepotnis macrochirus (mean weight 133 g) held for 8 weeks at 6°C and 20°C. Radio-tagged bluegills at 20°C had a mortality rate of 10% and tag loss rate of 15%. At 6°C, bluegills had no mortality or tag loss. Radio-tagged and reference fish fed in both 20°C raceways; however, a few reference fish appeared dominant at feeding time. This dominance by a few reference fish was also indicated by a large weight gain for three reference fish in each 20°C raceway. At 6°C. neither reference fish nor radio-tagged fish fed activity. Radio-tagged fish held at 20°C exhibited pelvic fin erosion, erythema and necrosis at the antenna exit and at suture insertions, and lost or loose sutures, effects not observed in other test fishes. Examination of fish held at 20°C also showed enclosure of the transmitters in a fibrous capsule and adhesion of visceral organs. Epithelialization over the incision occurred in radio-tagged bluegills at both temperatures, but there was little further healing at 6°C. At 20°C, tissue responses included chronic inflammation and dermal granulation. Radio-tagged fish did not appear to be more susceptible than reference fish to bacterial infection. Mortality, adverse morphological effects, altered behavior, and limited healing in bluegills suggest that implanted transmitters impaired their health. Thus, movement and habitat use data collected by telemetry for this species and perhaps for other panfishes should be interpreted with caution.
The freshwater fish Lepomis macrochirus (bluegill) is common to North American waters, and important both ecologically and as a sport fish. In 2001 an unknown virus was isolated from bluegills following a bluegill fish kill. This virus was identified as a picornavirus [termed bluegill picornavirus (BGPV)] and a diagnostic reverse transcriptase PCR was developed. A survey of bluegills in Wisconsin waters showed the presence of BGPV in 5 of 17 waters sampled, suggesting the virus is widespread in bluegill populations. Experimental infections of bluegills confirmed that BGPV can cause morbidity and mortality in bluegills. Molecular characterization of BGPV revealed several distinct genome characteristics, the most unusual of which is the presence of a short poly(C) tract in the 39 UTR. Additionally, the genome encodes a polyprotein lacking a leader peptide and a VP0 maturation cleavage site, and is predicted to encode two distinct 2A proteins. Sequence comparison showed that the virus is most closely related to a phylogenetic cluster of picornaviruses that includes the genera Aquamavirus, Avihepatovirus and Parechovirus. However, it is distinct enough, for example sharing only about 38 % sequence identity to the parechoviruses in the 3D region, that it may represent a new genus in the family Picornaviridae.
The modern sport fishery for salmonids in Wisconsin waters of Lake Michigan was begun during 1963-1969 with the stocking of rainbow trout Oncorhynchus mykiss, lake trout Salve/inns namaycush, brook trout 5". fontinalis, brown trout Salmo trulta, coho salmon O. kisutch, and Chinook salmon O. tshawytscha. The fishery grew rapidly during 1969-1985 as angler effort increased 10-fold, catch rate doubled, and catch increased 20-fold. The stocking and catch became increasingly dominated by Chinook salmon, with coho salmon and lake trout of secondary importance, and brown, rainbow, and brook trout of least importance. Trolling dominated the fishery, particularly by launched-boat anglers and, more recently, by moored-boat anglers. Charter boat trolling grew the most continuously and had the highest catch rates. The catch by trollers was dominated by Chinook and coho salmon and lake trout. Pier, stream, and shore anglers fished less overall, but had catch rates that were similar to launched-boat anglers. The catch by pier and shore anglers was spread among chinook and coho salmon, and lake, brown, and rainbow trout. The catch by stream anglers was dominated by chinook salmon. The percentage of stocked fish that were subsequently caught (catch ratio) was highest for fingerling chinook salmon (12.9%). Yearling brook trout, brown trout, coho salmon, lake trout, and rainbow trout had intermediate catch ratios (5.1-9.8%). Fingerling brook trout, brown trout, and lake trout had the lowest catch ratios (2.5-3.5%). The catch ratio for rainbow trout dropped from 9.8 to 5.1% after stocking with a different strain (the Shasta strain). Fingerling rainbow trout produced the lowest returns (< 0.5%). We derived stocking recommendations for each species and life stage based on these catch ratios, and catch objectives based on maintaining catch levels recorded during 1983-1985.
Seasonal population dynamics and maturation of the acanthocephalan Neoechinorhynchus pungitius from brook stickleback (Culaea inconstans) were investigated. Stickleback were collected monthly at Sioux Creek, Wisconsin from April 1981 to May 1982 (excluding December, January, and February). Forty-seven percent (292/620) were infected with N. pungitius, which exhibited seasonal periodicity in prevalence, mean intensity, and maturation. Prevalence and mean intensities were lowest in summer and increased through autumn owing to recruitment of juvenile and immature worms. Prevalence and mean intensity reached their peaks by April and May, and N. pungitius infrapopulations were composed primarily of mature worms. Egg production began in May and continued throughout early summer. Neoechinorhynchus pungitius males appeared shorter lived than females, as the June and July infrapopulations were comprised mostly of females. Prevalence and mean intensity of N. pungitius increased as brook stickleback length increased. There was no significant difference between numbers of male and female fish infected or between mean intensity and host sex.
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