Abstract Asian carps are classified as either bighead carp Hypophthalmichthys nobilis or silver H. molitrix by multiple presumptively diagnostic morphological characteristics; however, hybrids pose a dilemma. Fish sharing the characteristics of both species were observed in an Illinois River backwater (Calhoun County, Illinois) approximately 5 mi (8 km) upriver from confluence with Mississippi well two locations Pool 26 (Madison Illinois). Biopsied tissues individuals exhibiting mixed...

Hybridization among conspecifics in native and introduced habitats has important implications for biological invasions new ecosystems. Bighead (Hypophthalmichthys nobilis) silver carp (H. molitrix) are genetically isolated occur sympatry within their range. Following introduction to North America, however, introgressant hybrids have been reported throughout expanded range the Mississippi River Basin (MRB). The extent of introgression, both spatially generationally, is largely unknown....

Significant but subtle differentiation was detected for both microsatellite DNA and mitochondrial among four populations of American shad Alosa sapidissima . The data indicate that straying rivers is sufficient to permit only marginal population in this species, suggest individual river should be managed as distinct stocks. Comparison the Hudson Columbia populations, latter derived from former over 100 years ago, revealed a slight reduction variation founded halving DNA, consistent with...

Abstract A long history of human alterations has affected the hydrology, physical habitat and water quality most large river ecosystems. For more than a century, Illinois River Waterway been subject to channelization, damming, dredging, agricultural runoff industrial municipal effluents. This study evaluates how subsequent improvements in have influenced long‐term changes fish assemblages (1983–2010). We used five metrics characterize assemblages. These depicted shifts abundance biomass...

Alewife Alosa pseudoharengus, a small clupeid fish native to Atlantic Ocean, has recently (∼150 years ago) invaded the North American Great Lakes and despite challenges of freshwater environment its populations exploded disrupted local food web structures. This range expansion been accompanied by dramatic changes at all levels organization. Growth rates, size maturation, or fecundity are only few most distinct morphological life history traits that contrast two alewife morphs. A question...

Abstract: We investigated the conservation of genetic diversity during a restoration program for American shad ( Alosa sapidissima ) in Virginia U.S.A.). Restoration entailed capture wild Pamunkey River broodstock followed by production and release hatchery‐reared fry to supplement nearly extinct James population. To assess baseline donor recipient populations, we used five tri‐ tetra‐nucleotide microsatellite loci test heterogeneity among yearly subsamples from both rivers between early‐...

We investigated the geographic distribution of mitochondrial DNA (mtDNA) diversity American shad from 15 North rivers in 1992 with intent assessing sampling efficiency for future mixed-stock analysis. observed 116 haplotypes among 988 individuals assayed. Because no single or group completely discriminated river stocks regional complexes, we haplotype frequencies as stock descriptors. Analysis four unique indices divergence indicated that including rather than suppressing restriction site...

Bighead carp (Hypophthalmichthys nobilis) and silver (H. molitrix) are invasive species listed as US federally injurious under the Lacy Act. They have established populations in much of Mississippi River Basin (MRB; Mississippi, Illinois, Missouri rivers) capable producing fertile hybrids complex introgression. Characterizing composition this admixture requires a large set high-quality, evolutionarily conserved, diagnostic genetic markers to aid identification management these midst...

Des specimens d'alose savoureuse (Alosa sapidissima) ont ete preleves en 1992 et 1993 a 19 emplacements le long de la cote nord-americaine l'Atlantique. Les auteurs procede sur eux mesure variation l'ADNmt (N = 1888). tests du x 2 permis creer deux paires populations qu'il serait possible diviser 17 stocks. L'echantillonnage au fil des ans memes geographiques cause l'augmentation nombre d'haplotypes observes ainsi que d'ensembles un element (haplotypes chez seul sujet), mais proportion ces...

Abstract Chinook salmon Oncorhynchus tshawytscha were introduced into the Lake Michigan basin from 1966 to 1968 with transfer of fertilized eggs Green River Hatchery, Washington. In more than three decades since this founding, occur and are managed throughout Great Lakes as a mixture feral supplemented populations. To evaluate extent genetic diversity initial we examined pattern variation at 18 allozyme loci among populations in seven watersheds. We observed little divergence low...

The evolutionary sequence of events in the evolution reproductive barriers between species is at core speciation biology. Where premating fail, post-mating barriers, such as conspecific sperm precedence (CSP), gamete incompatibility (GI) and hybrid inviability (HI) may evolve to prevent production (often) costly offspring with reduced fitness. We tested role mechanisms for isolation two sunfish [bluegill (BG) Lepomis macrochirus pumpkinseed (PS) gibbosus] their first-generation hybrids....

1. Similarity indices are commonly used for multivariate analyses, estimations of β-diversity and assessments ecological impacts disturbances. Both statistical criteria have guided index selections. The former includes accuracy (i.e. how close an estimate is to the true value) precision repeatable different estimates are) while latter focused on detection known assemblage changes or environmental gradients. 2. These two types criteria, however, often lead conflicting recommendations...

In 1996, fishery administrators from every U.S. state were surveyed about an array of coldwater management topics ranging the composition resources, to threats facing expertise and strategies employed by agency. Administrators in 49 states returned completed surveys provided information on general challenges resources conditions under which these are managed. For example, 47 managed fisheries. Of these, 38 cited habitat-related problems as most commonly identified obstacles maintaining...

North American paddlefish Polyodon spathula historically occurred in the Mississippi, Saint Lawrence, and Alabama rivers, as well several other Gulf of Mexico coastal drainages. Recent population declines some locations local extirpations others purportedly have been due to habitat loss, overharvest, biotic abiotic changes riverine ecosystems. Mitigation for these has emphasized hatchery production supplemental stocking programs, which use a number geographical sources parental stock. To...

Many ecosystems have been dramatically affected by non-native species, but not all such species strong deleterious effects. American shad, Alosa sapidissima, a fish native to the Atlantic coast of North America, was transplanted Pacific in late nineteenth century and quickly colonized many US rivers. Their increased abundance Columbia River coincided with declines anadromous salmon trout, adult shad now greatly outnumber returning salmonids. This paper reviews evidence for possible...

Bull trout (Salvelinus confluentus) is a species of conservation concern–listed as “threatened” under the Endangered Species Act–throughout its native range in western United States. The authors were assembled by Clark Fork River Aquatic Implementation Team, composed biologists representing Montana Fish, Wildlife and Parks (MFWP); Idaho Department Fish Game (IDFG); Avista Corporation, to provide genetics perspective assist those managers charged with stewardship bull populations occupying...