Muskellunge Research Articles

Growth of pike Esox lucius L. in Lake Rubikiai (Lithuania)

Summary The aim of the study was to determine the growth rate and growth parameters of pike Esox lucius L. in the mesotrophic Lake Rubikiai and to evaluate species growth in light of environmental conditions in Lithuanian lakes of different limnologic types. A total of 204 pike specimens were caught in two subsequent years, April 2005 and April 2006, in Lake Rubikiai. Six age classes (2–7 years of age) for males and 10 age classes (3–12 years of age) for females were identified by scale readings; 2- to 4-year-old males and 4- to 7-year-old females prevailed. Total length of pike ranged from 26.5 to 107 cm and weight from 106 to 7600 g. There were no statistically significant differences (Student’s t-test, P > 0.1) between mean lengths and weights of males and females of the same age. Von Bertalanffy growth parameters for the entire population were: L∞ = 131.7 cm, k = 0.1530 year−1, to = −0.0398 year. Calculated overall growth performance index ϕ′ was 3.42. The length-weight relationship was described by the equation . The growth rate of pike in Lake Rubikiai was higher than in most other investigated Lithuanian lakes. Pike from Lake Rubikiai are characterized by average growth, compared to other populations from various geographical locations. No significant differences were established between the growth of pike in mesotrophic and eutrophic lakes. Pike growth rate did not correlate with lake surface area, maximum or mean depth, and negatively correlated with bogginess in mesotrophic lakes and limpidity and bogginess in eutrophic lakes (P < 0.05).

Implementation of Genetic Conservation Practices in a Muskellunge Propagation and Stocking Program

Conservation of genetic resources is a challenging issue for agencies managing popular sport fishes. To address the ongoing potential for genetic risks, we developed a comprehensive set of recommendations to conserve genetic diversity of muskellunge (Esox masquinongy) in Wisconsin, and evaluated the extent to which the recommendations can be implemented. Although some details are specific to Wisconsin's muskellunge propagation program, many of the practical issues affecting implementation are applicable to other species and production systems. We developed guidelines to restrict future broodstock collection operations to lakes with natural reproduction and to develop a set of brood lakes to use on a rotational basis within regional stock boundaries, but implementation will require considering lakes with variable stocking histories. Maintaining an effective population size sufficient to minimize the risk of losing alleles requires limiting broodstock collection to large lakes. Recommendations to better approximate the temporal distribution of spawning in hatchery operations and randomize selection of brood fish are feasible. Guidelines to modify rearing and distribution procedures face some logistic constraints. An evaluation of genetic diversity of hatchery‐produced fish during 2008 demonstrated variable success representing genetic variation of the source population. Continued evaluation of hatchery operations will optimize operational efficiency while moving toward genetic conservation goals.

Factors Affecting Recruitment of Age‐0 Muskellunge in Escanaba Lake, Wisconsin, 1987–2006

AbstractWe modeled variation in recruitment (R) of age‐0 muskellunge Esox masquinongy to identify factors influencing their abundance in Escanaba Lake, Wisconsin. Muskellunge R declined over the study period and ranged from 0.00 to 1.85 age‐0 fish/km of shoreline (mean = 0.42 age‐0 fish/km of shoreline). A Ricker stock–recruitment model determined that the following factors explained 88% of the variation in annual R of age‐0 muskellunge between 1987 and 2006: abundance and age structure of the adult muskellunge population, abundance of bluntnose minnow Pimephales notatus, abundance of age‐3 and older (age‐3+) walleyes Sander vitreus, abundance of age‐0 white suckers Catostomus commersonii, and coefficient of variation (CV) of May water temperatures. Abundance of adult muskellunge (≥76.2 cm total length) accounted for only 1% of the variation in R and showed no significant relationship with R. Abundance of bluntnose minnow improved the model fit to 40% of the variation in R and indicated that higher R was achieved with greater numbers of bluntnose minnow. The average age of adult muskellunge further improved the model fit to 59% of the variation in R, suggesting that R increased when more young adults were present in the population. The abundance of age‐3+ walleyes enhanced the model fit to 69% of the variation in R and indicated that greater R occurred with high numbers of walleyes. The abundance of age‐0 white suckers improved the model to explain 77% of the variation in R and indicated that more recruits occurred when numbers of age‐0 white suckers were low. Finally, the CV of May water temperatures further improved the model to explain 88% of the variation in R and signified that lower variability in May water temperatures was beneficial to recruitment success. We interpret the model results to mean that muskellunge R in Escanaba Lake is regulated by the reproductive potential of the adult muskellunge population, forage availability, variation in May water temperatures, and other community dynamics.

Evaluation of the aquatic habitat and fish assemblage in an urban reach of the historic Rideau Canal, Ottawa, Canada: Implications for management in an engineered system

The historic Rideau Canal (built in the 1800s) in eastern Ontario, Canada is a heavily managed and engineered ecosystem, popular for recreational boating and sport fishing in the summer and ice skating in the winter. However, little is actually know about the fish and aquatic macrophyte communities, particularly in the urban reach in Ottawa between Hartwell’s Lock and the outflow of Dows Lake. The objective of this study was to examine the extent to which fish and macrophytes varied among different natural and engineered habitat/substrate types across the period when the canal is at navigational water levels. Five gross habitat types were identified, consisting of gravel, silt/sand, rip-rap/gabion basket, boulder and concrete wall habitats. Replicate transects were established in the littoral zone, representing the different habitat types. Snorkel surveys were conducted on a biweekly basis, where fish species and aquatic macrophytes within the transects were quantified. Supplementary data on fish populations was obtained through seine net sampling as well as angler interviews and visual observations. The fish community was characterized as a reasonably simple warmwater assemblage, dominated by centrarchids (e.g., pumpkinseed [Lepomis gibbosus], bluegill [L. macrochirus], and largemouth bass [Micropterus salmoides]). In fact, more than 90% of all fish encountered (snorkel surveys and seine netting) belonged to the centrarchid family. None of the 17 fish species encountered in the reach were considered “at risk” in Canada, although the system supports one of the few urban muskellunge (Esox masquinongy) populations in the world and provides a range of urban recreational fishing opportunities for sportsfish. Fish diversity metrics (e.g., diversity, richness, evenness) varied little among habitat types, perhaps reflecting the fact that vegetation communities were reasonably homogeneous, largely dominated by the exotic Eurasian water milfoil (Myriophyllum spicatum). This research provides managers with the first detailed information on the aquatic ecology in this engineered urban ecosystem which will enable relevant government agencies (e.g., Parks Canada) to better balance the iconic cultural values of national significance with their mandate to protect the ecological integrity of the canal ecosystem.

The Laurentian Great Lakes strain (MI03) of the viral haemorrhagic septicaemia virus is highly pathogenic for juvenile muskellunge, Esox masquinongy (Mitchill)

The Great Lakes strain of viral haemorrhagic septicaemia virus (VHSV) isolated from adult subclinical muskellunge, Esox masquinongy (Mitchill), in Lake St. Clair, MI, USA was shown to be highly pathogenic in juvenile muskellunge through intraperitoneal (i.p.) injection and waterborne challenge. Mortality began as early as 3 days after exposure in waterborne challenged fish, whereas fish infected by the i.p. route experienced the first mortality by 5 days post-infection (p.i.). The median lethal intraperitoneal injection dose (IP-LD(50)) was approximately 2.21 plaque forming units (PFU) as opposed to the median lethal immersion challenge dose (IM-LD(50)) of 1.7 x 10(4) PFU mL(-1). A high, medium and low dose of infection caused acute, subacute and chronic progression of the disease, respectively, as was evident by the cumulative mortality data. Clinical signs of disease observed in dead and moribund fish were very pale gills, dermal petechial haemorrhages along the flanks, severe nuchal haemorrhages, intramuscular haemorrhages at the fin-muscle junction and focal haemorrhaging on the caudal peduncle. Internal lesions included livers that were pale, discoloured and friable, and kidneys that were either congested or degenerative in appearance, and petechial to ecchymotic haemorrhages on the swim bladder wall. Histopathologic examination demonstrated massive haemorrhages in the swimbladder wall and muscle, severe vacuolation and multifocal necrosis of the liver, multifocal necrosis of the gills and depletion of lymphoid tissues within the spleen. Kidney tissues also exhibited a mixed pattern of degeneration that included tubular necrosis, interstitial oedema and congestion. Virus was recovered from kidney and spleen tissues through tissue culture and reverse transcriptase-polymerase chain reaction (RT-PCR).

Spatial ecology of adult muskellunge (Esox masquinongy) in the urban Ottawa reach of the historic Rideau Canal, Canada

The Rideau Canal in Canada was constructed in the 1800s to enable strategic military and commercial transport in eastern Ontario between Lake Ontario and the Ottawa River. Today, the Rideau Canal is managed by Parks Canada and remains an engineered ecosystem, particularly in the urban Ottawa reach (7 km long) where it is largely channelized and is partially drained during the winter to protect canal infrastructure (i.e., locks) and provide recreational opportunities (i.e., skating). Interestingly, the Ottawa reach of the Rideau Canal supports one of the few wild urban muskellunge (Esox masquinongy) fisheries in North America supported by natural reproduction. However, little is known about the spatial ecology, residency patterns or survival of this apex freshwater predator in urban environments or canal systems. Radio-telemetry was used to study adult (N = 10; total size range of 64 to 122 cm) muskellunge in the Ottawa reach of the Rideau Canal over a multiple year period. The seasonal movements and home range of muskellunge were greatest during spring corresponding with the period when water levels in the canal were raised and muskellunge were presumably seeking out suitable spawning habitats following ice-off. During the summer fish ranged throughout the entire 7 km urban reach of the canal and by early fall muskellunge moved to the deeper parts of the reach and became largely restricted to an embayment known as Dow's Lake prior to the lowering of the canal where they stayed for the entire winter. The same pattern of seasonal movements persisted across several years. None of the tagged muskellunge were stranded from the fall canal drainage. One fish emigrated from the urban reach of the canal during the study period, moving upstream through a lock to an exurban reach. In addition, a single tagged fish died from a winterkill event. Environmental influences such as seasonality and water depth (associated with canal operations) are believed to be the primary mechanisms contributing to habitat selection and movement patterns of muskellunge in this reach of the Rideau Canal. Data on the spatial ecology of muskellunge in the urban reaches of the Rideau Canal will inform management of this unique population of fish to ensure that the historic and ecological values are balanced to preserve this iconic Canadian natural heritage site and its biota.

Short‐ and Long‐Term Evaluation of Passive Integrated Transponder and Visible Implant Elastomer Tag Performance in Muskellunge

AbstractFisheries professionals charged with managing muskellunge Esox masquinongy frequently seek population information that requires the ability to identify cohorts as well as individuals; hence, reliable tagging methods are needed. Our approach was to simultaneously assess multiple marking techniques on different life stages of muskellunge over short and long time scales. We evaluated the short‐term detection of visible implant elastomer (VIE) and passive integrated transponder (PIT) tags in muskellunge fingerlings in experimental ponds. We compared survival (relative to that of control fish) and tag retention for two PIT tagging locations (the cheek and dorsal musculature) and one VIE location (the jaw). Overwinter survival did not differ between tagged and untagged fish (84–98%), but overwinter PIT tag retention was lower for the cheek (92%) than the dorsal musculature (100%). We also fin‐clipped and VIE‐tagged (jaw) 1,651 muskellunge fingerlings from 1997 to 2002 to evaluate long‐term tag retention in a broodstock lake. In addition, 125 adult muskellunge were captured and PIT‐tagged from 2003 to 2006. Muskellunge were sampled annually with trap nets and electrofishing during spring and fall. Only 2 VIE tags were detected in adults marked as fingerlings. The proportion of PIT‐tagged adults recaptured ranged from 52% to 84% during the sampling period. Our results indicate that both VIE and PIT tags are viable short‐term marks for muskellunge fingerlings, while PIT tags appear to be reliable long‐term tags when implanted in the dorsal musculature of adults.

Effects of Fin‐Clipping on the Foraging Behavior and Growth of Age‐0 Muskellunge

AbstractWe evaluated the effects of fin‐clipping on the foraging behavior and growth of age‐0 muskellunge Esox masquinongy. Fish were subjected to one of six fin‐clipping treatments (one or both pectoral and pelvic fins, all paired fins, and a nonclipped control) and allowed to forage on golden shiners Notemigonus crysoleucas in laboratory pools (1.7 m in diameter). Observations of foraging behavior showed that muskellunge required a similar number of stalks, follows, and strikes to capture prey regardless of fin clip. Capture efficiencies (56%) were also similar among treatments. In outdoor pools (1.5 m in diameter), the growth and food conversion efficiency of fin‐clipped muskellunge feeding on golden shiners over a 1‐month period did not differ from those of unclipped controls. Fin removal did not compromise foraging behaviors and growth for juvenile muskellunge foraging on moderately evasive prey, and fish showed immediate behavioral compensation.

Molecular characterization of the Great Lakes viral hemorrhagic septicemia virus (VHSV) isolate from USA

BackgroundViral hemorrhagic septicemia virus (VHSV) is a highly contagious viral disease of fresh and saltwater fish worldwide. VHSV caused several large scale fish kills in the Great Lakes area and has been found in 28 different host species. The emergence of VHS in the Great Lakes began with the isolation of VHSV from a diseased muskellunge (Esox masquinongy) caught from Lake St. Clair in 2003. VHSV is a member of the genus Novirhabdovirus, within the family Rhabdoviridae. It has a linear single-stranded, negative-sense RNA genome of approximately 11 kbp, with six genes. VHSV replicates in the cytoplasm and produces six monocistronic mRNAs. The gene order of VHSV is 3'-N-P-M-G-NV-L-5'. This study describes molecular characterization of the Great Lakes VHSV strain (MI03GL), and its phylogenetic relationships with selected European and North American isolates.ResultsThe complete genomic sequences of VHSV-MI03GL strain was determined from cloned cDNA of six overlapping fragments, obtained by RT-PCR amplification of genomic RNA. The complete genome sequence of MI03GL comprises 11,184 nucleotides (GenBank GQ385941) with the gene order of 3'-N-P-M-G-NV-L-5'. These genes are separated by conserved gene junctions, with di-nucleotide gene spacers. The first 4 nucleotides at the termini of the VHSV genome are complementary and identical to other novirhadoviruses genomic termini. Sequence homology and phylogenetic analysis show that the Great Lakes virus is closely related to the Japanese strains JF00Ehi1 (96%) and KRRV9822 (95%). Among other novirhabdoviruses, VHSV shares highest sequence homology (62%) with snakehead rhabdovirus.ConclusionPhylogenetic tree obtained by comparing 48 glycoprotein gene sequences of different VHSV strains demonstrate that the Great Lakes VHSV is closely related to the North American and Japanese genotype IVa, but forms a distinct genotype IVb, which is clearly different from the three European genotypes. Molecular characterization of the Great Lakes isolate will be helpful in studying the pathogenesis of VHSV using a reverse genetics approach and developing efficient control strategies.

One‐Year Retention of Passive Integrated Transponders in Adult Muskellunge, and Applications to Broodstock Management

AbstractMuskellunge Esox masquinongy are long‐lived fish that typically occur at low densities. Tracking the history of individuals used as broodstock allows accurate determination of the effective population size and is essential to meeting genetic objectives for management‐oriented hatchery propagation programs. We tested the utility of passive integrated transponder (PIT) tags for tracking individual muskellunge. We placed PIT tags in the cheeks of 291 adult muskellunge netted during the spring spawning season in two Wisconsin lakes. Partial fin clips were used as a secondary mark. The lakes were sampled during the following year, and 73 fish with fin clips were recovered in a sample of 271 fish. The one‐year tag retention rate was 90.4% in the two lakes. Six fish without functional tags were examined for the presence of broken or malfunctioning tags, and all were missing tags. The use of PIT tags is feasible for adult muskellunge and is useful for maintaining individually based broodstock records.

Interactions of multiple predators with different foraging modes in an aquatic food web

Top predators can have different foraging modes that may alter their interactions and effects on food webs. Interactions between predators may be non-additive resulting from facilitation or interference, whereas their combined effects on a shared prey may result in emergent effects that are risk enhanced or risk reduced. To test the importance of multiple predators with different foraging modes, we examined the interaction between a cruising predator (largemouth bass, Micropterus salmoides) and an ambush predator (muskellunge, Esox masquinongy) foraging on a shared prey (bluegill sunfish, Lepomis macrochirus) with strong anti-predator defense behaviors. Additive and substitution designs were used to compare individual to combined predator treatments in experimental ponds. The multiple predator interaction facilitated growth of the cruising predator in the combined predator treatments, whereas predator species had substitutable effects on the growth of the ambush predator. The combined predator treatments created an emergent effect on the prey; however, the direction was dependent on the experimental design. The additive design found a risk-reducing effect, whereas the substitution design found a risk-enhancing effect for prey fish. Indirect effects from the predators weakly extended to lower trophic levels (i.e., zooplankton community). Our results highlight the need to consider differences in foraging mode of top predators, interactions between predators, and emergent effects on prey to understand food webs.

Walleye and Muskellunge Movement in the Manitowish Chain of Lakes, Vilas County, Wisconsin

AbstractWe quantified within‐year and between‐year movement of walleyes Sander vitreus and muskellunge Esox masquinongy in the Manitowish Chain of 10 interconnected lakes in Vilas County, Wisconsin. Beginning in May 2004, we marked 7,427 walleyes (55–2,720 fish/lake) and 491 muskellunge (24–99 fish/lake) with T‐bar anchor tags and marked 33 walleyes and 36 muskellunge with radio tags. Tags were recaptured and recovered through October 2005 via fyke‐netting, electrofishing, angling, and spearing. Anchor tag loss averaged 2.9% for walleyes and 2.1% for muskellunge. Of 1,752 anchor‐tagged walleyes (19–555 fish/lake), 81% (54–90% per lake) were recovered in the same lake in which they were tagged. Of the 95 muskellunge tagged (1–18 fish/lake), 53% (0–100% per lake) were recovered in the same lake in which they were tagged. For radio‐tagged fish, 82% (27 of 33 fish) of walleyes and 50% (18 of 36 fish) of muskellunge were recovered in the same lake in which they were tagged. Of 1,153 anchor tag returns for walleyes (8–326 fish/tag group and 6–340 fish/lake) and 57 anchor‐tag returns for muskellunge (1–17 fish/tag group and 1–12 fish/lake), 76% of walleyes (37–98% per lake) and 45% of muskellunge (0–100% per lake) were found in the same lake in spring 2004 and spring 2005. Our results indicate that most walleyes remained in the same lake during the year of tagging and between years, whereas half of all muskellunge did not remain in the same lake during the tagging year or between years. We recommend that walleye angling and spearing fisheries be managed for individual lakes and that muskellunge fisheries be managed for the entire chain of lakes.

The Genetic Legacy of Stocking Muskellunge in a Northern Minnesota Lake

AbstractThe effects of stocked fish on native populations of the same species are poorly understood. During the 1960s‐1980s, the Minnesota Department of Natural Resources (MNDNR) stocked muskellunge Esox masquinongy derived from Shoepack Lake in the Hudson Bay drainage of northern Minnesota into Moose Lake in the Upper Mississippi River drainage. In the mid‐1980s, the MNDNR recognized that stocked Shoepack Lake‐strain fish (hereafter, Shoepack strain) were not attaining large sizes, and sources were switched statewide; subsequently, muskellunge from a Wisconsin hatchery were stocked once into Moose Lake. We used 14 microsatellite DNA markers to estimate the genetic contribution by each source population to muskellunge sampled in four different years from 1981 to 2004, and we evaluated the effects of Shoepack‐strain ancestry on fish size. Two samples in the 1980s had mostly fish with a single ancestry; thus, these fish were probably Shoepack‐strain fish stocked a few years earlier or native fish. By 2004, when most fish would have been naturally produced in the lake, contributions from all three source populations were detected, including admixed individuals from crosses among all ancestral sources. The estimated ancestry by source was 52% native Moose Lake ancestry, 29% Wisconsin strain, and 19% Shoepack strain, with 24% of the individuals having pure Moose Lake ancestry. Fish without Shoepack‐strain ancestry had a greater median length than did those with Shoepack‐strain ancestry and had a greater proportion of legal‐sized individuals (total length ≥ 1,016 mm) in the population. In contrast, Moose Lake and Wisconsin‐strain descendents were common among all sizes of fish. Management options include doing nothing, accepting that extensive introgression has already occurred, or manipulating the population by either stocking to dilute Shoepack‐strain ancestry or genetic screening to purge the population of Shoepack‐strain ancestry.

Assessment of oxidative stress and histopathology in juvenile northern pike ( Esox lucius) inhabiting lakes downstream of a uranium mill

Lakes receiving effluent from the Key Lake uranium mill in northern Saskatchewan contain elevated trace metals, some of which are associated with increased reactive oxygen species (ROS) in cells and tissues causing oxidative stress. The potential for oxidative stress was assessed in juvenile (age 1+) northern pike ( Esox lucius) collected from two exposure (high and low) and one reference lake near the Key Lake operation. The concentrations of total, reduced and oxidized glutathione and the ratio of oxidized to reduced glutathione in liver and kidney did not differ significantly among pike collected from exposure and reference lakes, with the exception of low exposure pike kidney that had significantly greater oxidized glutathione and ratio of oxidized to reduced glutathione. The concentrations of by-products of lipid peroxidation (malondialdehyde and 4-hydroxyalkenal) were significantly greater in kidney of pike collected from the reference lake compared to both exposure lakes. The activity of the antioxidant enzyme glutathione peroxidase in liver was greater in pike collected from the high exposure lake compared to the reference lake. Histopathological evaluations revealed greater pathology in reference lake pike as indicated by a greater number of pyknotic and fragmented nuclei and dilated tubules as well as a thickening of Bowman's capsule in kidney, and as a thickening of the primary filament epithelial padding in gills. In liver, hepatocyte morphology, including transsectional area and degree of vacuolation, differed among lakes without any clear signs of pathology. Trace metal analyses of muscle showed that eight elements (arsenic, cobalt, copper, iron, molybdenum, selenium, thallium, and uranium) were significantly elevated in pike collected from both exposure lakes compared to reference. These results provide only limited evidence of oxidative stress in exposure pike tissues and no evidence of histopathology despite indications that trace metals, most notably arsenic and selenium, were bioaccumulating in tissue.

Novel Tools for Analyzing Proportional Size Distribution Index Data

AbstractProportional size distribution (PSD) indices are convenient measures for numerically summarizing size structure of fish populations. Several novel methods for analyzing PSD index data were examined as a means for potentially improving inferences of size structure: generalized linear mixed modeling, calculation of location quotients, and simultaneous construction of 100(1 − α)% confidence intervals for PSD indices through multinomial modeling. The methods are demonstrated using simulated and previously published PSD index data. Generalized linear mixed modeling was used to (1) conduct a model selection analysis of PSD index data relative to a change in harvest regulation for walleyes Sander vitreus, (2) partition the variance of PSD index data among spatial, temporal, and environmental attributes, and (3) nonlinearly relate PSD data to adult density for largemouth bass Micropterus salmoides. The location quotient, which is an index for describing relative concentration of proportional data, was used to describe spatial and temporal localization of largemouth bass and walleye PSD index data. Finally, a modified method of constructing simultaneous 100(1 − α)% confidence intervals for multinomial proportions was used to produce 95% confidence intervals for traditional and incremental PSD indices based on length frequency data from muskellunge Esox masquinongy. The approaches described herein can assist fishery biologists in size structure assessments of fish populations and ultimately aid in cost‐effective fisheries management.

Development of new microsatellite loci and multiplex reactions for muskellunge (Esox masquinongy)

The muskellunge (Esox masquinongy) is a valued fisheries species throughout its native range. Numerous studies have documented performance and phenotypic differences among muskellunge populations, but genetic markers for assessment have been lacking. We characterized 14 microsatellite loci and developed five multiplex polymerase chain reactions. Successful amplification of northern pike (Esox lucius) was observed for seven loci. These microsatellites will be useful for analysing population structure, performance characteristics of propagated strains, and helping to develop and monitor hatchery management guidelines for muskellunge.

Ecology and management of northern pike in Wisconsin

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.

Development of new microsatellite loci and multiplex reactions for muskellunge (Esox masquinongy)

Development of new microsatellite loci and multiplex reactions for muskellunge (Esox masquinongy)

Survival, Growth, and Tag Retention in Age‐0 Muskellunge Implanted with Passive Integrated Transponders

AbstractMark–recapture studies are an important component of fisheries research and management. Underlying assumptions of such studies include minimal tag loss and negligible effects on the behavior, fitness, and survival of tagged individuals. Passive integrated transponder (PIT) tags are becoming increasingly commonplace, largely because of their small size, ease of implantation, longevity, and reportedly high rates of retention. We evaluated tag retention and survival and growth effects on age‐0 muskellunge Esox masquinongy marked with PIT tags at two implantation sites, the peritoneal cavity and the dorsal musculature, during overwinter trials in Illinois and Wisconsin. For both trials, no significant differences in survival (88.0–89.8%), relative daily growth (0.0006–0.00062 mm·mm−1·d−1), or tag retention (99.5–99.8%) were observed among the two implantation groups and a control group. Survival and tag retention were also similar between trials. Our findings suggest that PIT tags implanted either in the peritoneal cavity or the dorsal musculature are acceptable for use in marking age‐0 muskellunge.

Mortality event in freshwater drum Aplodinotus grunniens from Lake Ontario, Canada, associated with viral haemorrhagic septicemia virus, Type IV

A mortality event primarily affecting freshwater drum Aplodinotus grunniens was noted during April and May 2005 in the Bay of Quinte, Lake Ontario, Canada. A conservative estimate of the number of dead drum was approximately 100 metric tonnes. Large numbers of dead round goby Neogobius melanostomus were also seen, as well as a few muskellunge Esox masquinongy. In the drum, there was a consistent histological pattern of variably severe panvasculitis, a necrotising myocarditis, meningoencephalitis and a segmental enteritis. Moderate numbers of bullet-shaped viral particles consistent with a rhabdovirus were identified by transmission electron microscopy (TEM) in affected heart tissue. Following primary isolation from pooled tissues on fathead minnow (FHM) cells, a morphologically similar virus, approximately 165 x 60 nm in size, was visualised. Identification of the isolate as viral haemorrhagic septicemia virus (VHSV) was confirmed by enzyme immunoassay and by polymerase chain reaction. An appropriately sized product (468 bp) of the G-glycoprotein gene (nucleotides [nt] 340 to 807) was generated with RNA extracted from FHM cell supernatant. Analysis of a 360 nt partial glycoprotein gene sequence (nt 360 to 720) indicated a 96.4 to 97.2% nucleotide identity with known strains of North American (NA) VHSV. Analysis using Neighbour-joining distance methods assigned the isolate to the same lineage as the NA and Japanese isolates (Genogroup IV). However, there was sufficient sequence divergence from known NA VHSV isolates to suggest that this isolate may represent a distinct subgroup. The effects of ongoing mortality in freshwater drum and in multiple species during spring 2006 suggest that this newly recognised virus in the Great Lakes will have continued impact in the near future.