摘要:

Frequencies of external and grossly visible liver tumors were high in brown bullheads Ictalurus nebulosus from Black River, an industrialized Lake Erie tributary. Skin and liver tumors were lacking in brown bullheads from Buckeye Lake, a reference site, and the incidence of lip tumors was low (<2%). Liver tumors, primarily cholangiocarcinomas, increased significantly (P < 0.05) with age in Black River brown bullheads, occurring in 28–44% of the 4-year-old fish collected in 1980–1982. External tumors did not increase consistently with age. Within year classes, the occurrence of grossly observable liver tumors was higher in fall than in spring. Liver tumor incidence was not correlated with sex. Organic contaminants were higher in brown bullheads from the Black River than in those from Buckeye Lake. Polynuclear aromatic hydrocarbons were particularly high, including carcinogens such as benz[a]anthracene and benzo[a]pyrene (B[a]P). Limited electron microscopy of cholangiocarcinomas provided no evidence of virus. Since brown bullhead have the ability to hepatically activate B[a]P, and since B[a]P has been shown to induce cancer in fish, the hypothesis of a chemical etiology for the tumors in the Black River brown bullheads best fits the available data.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<79:TFACCI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The metallothionein-human growth hormone fusion gene (MThGH), constructed by fusing the mouse metallothionein promoter with the human growth hormone gene, was microinjected into the cytoplasm of one-cell embryos of channel catfish Ictalurus punctatus. The 3-week-old fish that developed were analyzed for integrated copies of the MThGH gene. Two of 10 animals contained MThGH sequences that comigrated with genomic DNA of high molecular weight in southern blots. The MThGH sequences were organized in head-to-tail tandem arrays that are characteristic of foreign genes integrated into recipient cell genomes. These data strongly suggest that the MThGH genes are stably integrated into chromosomal DNA, and that transgenic channel catfish can be generated by cytoplasmic injection of early embryos.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<87:TOTMGH>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Triploid fish hybrids frequently survive better than diploid hybrids. Tiger trout are a sterile hybrid between female brown trout Salmo trutta and male brook trout Salvelinus fontinalis; they have a poor early survival rate but a good growth rate. We produced triploid tiger trout by heat shock treatments of fertilized eggs and examined their survival and growth under hatchery conditions. Triploid tiger trout survived better to the initiation of feeding (34%) than did diploid tiger trout (5%) but had lower survival than brown trout (70%). Triploid tiger trout had similar survival to and better growth than brown trout when the two groups were reared together for 239 d after the initiation of feeding. Analysis of the asymmetry of bilateral meristic traits indicated higher developmental stability in the triploid hybrids than in the diploid hybrids. Expression of both parental alleles of enzyme loci, determined by protein electrophoresis, confirmed the hybrid nature of the offspring. Triploid hybrids could be distinguished reliably from diploid hybrids by differences in relative expression of maternal and paternal alleles at some, but not all, loci. Triploid tiger trout appear to be a vigorous hybrid that could be of particular value in situations where allsterile trout populations are desired for stocking.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<92:PADSOT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Stunting in freshwater fish is a common phenomenon occurring in a wide variety of species throughout the world. It has been speculated that stunted fish have been selected for slow growth rate and will be genetically different in this respect from normal populations. Yellow perch Perca flavescens and pumpkinseeds Lepomis gibbosus in Lac Hertel, Québec, have been stunted for at least 20 and 12 years, respectively. To test for a genetic component to the stunting of the Lac Hertel fish, we used optimal laboratory conditions to raise 1-year-old yellow perch and pumpkin-seeds from Lac Hertel and from two comparable nonstunted populations (Lakes Memphremagog and Massawippi, Québec). The hypothesis tested was that Hertel fish would grow more slowly than fish from the other two lakes (which should grow at similar rates). No differences were found in either the growth or the mean: Variance relationship. Thus, the differences in growth in the field are principally an effect of environmental variation, not genetic differentiation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<98:TOGDIG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Introgressive hybridization has important management and evolutionary consequences in regard to the maintenance of the integrity of gene pools and the acquisition of new alleles by means other than mutation. Among North American cypriniform fishes, hybridization often occurs between historically allopatric forms placed into sympatry via human activities and between sympatric forms inhabiting a modified environment. In the Colorado River system, several native catostomids are known to hybridize, including flannelmouth sucker Catostomus latipinnis and razorback sucker Xyrauchen texanus. Allozymic data enabled direct quantification of presumed introgression which was in the range of 0–5% toward flannelmouth sucker and 0–3% toward razorback sucker. Levels of presumably introgressed genes in the stock of razorback sucker from the Dexter Fish Hatchery were as low as or lower than those of the parental stock population from Lake Mohave.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<103:PDAIHO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Distribution, habitat use, and relative abundance of the rare razorback sucker Xyrauchen texanus were evaluated by the capture of 323 of the fish and by the use of radiotelemetric data from six fish. Razorback suckers in the Green River were not uniformly distributed; they were most abundant in flat-water sections, and none were collected in white-water canyons. Razorback suckers displayed spawning movements in spring, and three spawning reaches were identified by the collection of 101 fish in breeding condition. Larval razorback suckers were collected downstream of the spawning reaches, but no juveniles were collected, indicating little or no successful recruitment. Spawning preferences were deduced from the capture of 52 ripe razorback suckers, between May 3 and June 15, 1984, and between April 22 and June 5, 1986, over sand and gravel substrates. Water temperatures at the points of capture ranged from 10 to 18°C, averaging 15°C. Catch data suggested that the razorback sucker population is small, and that the species is more rare than the endangered Colorado squawfish Ptychocheilus lucius. Low numbers, little growth, and no apparent recruitment suggest that this species will disappear in nature as old fish die and are not replaced.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<111:DRAHUO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Digestive tracts of 34 preserved adult razorback suckers Xyrauchen texanus from Lake Mohave, Arizona-Nevada, were examined. Contents were dominated by planktonic crustaceans, diatoms, filamentous algae, and detritus. The species is equipped for and apparently pursues a planktivorous habit, but benthic materials in the diet indicate bottom feeding also occurs.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<117:DTCOAR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Eighty specimens of striped bass Morone saxatilis were sampled from commercial catches during the summer and fall of 1985 along the north shore of Minas Basin and Cobequid Bay, Nova Scotia, for stomach content analysis. Striped bass fed on invertebrates as young of year. They became more piscivorous with age, although invertebrates remained an important component of the diets of older fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<119:FOSBIT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/00028487.1987.10492899

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor