摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f74-239

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Geosmin has been isolated and identified, using gas-chromatographic, mass-spectrometric and organoleptic analysis, as the principal compound responsible for the muddy flavor in fish from various saline lakes in western Canada. A method for quantitative estimation of geosmin has been described and evaluated. Placing of muddy-flavored rainbow trout (Salmo gairdneri) in clean water resulted in reduction of flavor to the borderline level between 3 and 5 days, and of geosmin concentration from 1.1 to 0.3 μg/100 g of flesh in 14 days. The taste threshold level of geosmin was estimated to be 0.6 μg/100 g flesh.

ISSN:0706-652X    

DOI:10.1139/f74-240

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Observed regularities in the size composition of pelagic ecosystems are explained by a theoretical model based on trophic processes. The model assumes, in accord with available evidence, that prey and predator sizes are simply related, and that growth and metabolism satisfy similar functions of body (particle) size when averaged over entire trophic levels. The model appears suited to other community types that satisfy these conditions, and suggests that trophic processes are complementary to competitive displacement in determining that particle density is a linear function of the logarithm of particle size.

ISSN:0706-652X    

DOI:10.1139/f74-241

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Icelanonchohaptor fyviein. sp., from the gills of quillback,Carpiodes cyprinus(LeSueur), is described andAnonchohaptor anomalumMueller 1938 is redescribed. A new host record, longnose sucker,Catostomus catostomus(Forster), is reported forAnonchohaptor anomalumMueller 1938.

ISSN:0706-652X    

DOI:10.1139/f74-242

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Wild underyearling coho salmon,Oncorhynchus kisutch, in a stream aquarium were exposed to sublethal concentrations of the organophosphate insecticide Sumithion (0.10, 0.23, 0.48, and 0.75 ppm fenitrothion). After 2-h exposure at 0.48 and 0.75 ppm the pattern of behavior changes indicated physiological impairment. All behaviors involving locomotion, including some comfort behaviors, virtually ceased. Many fish, unable to maintain position, were swept downstream. Only coughing increased in frequency with insecticide concentration, providing an indicator of physiological stress. In the 0–0.23 ppm range social behaviors and feeding markedly decreased in frequency whereas comfort movements generally increased; feeding was depressed at concentrations as low as 0.1 ppm. Of the various behaviors examined, feeding probably provides the best combination of a sensitive indicator of low level contamination by an organophosphate insecticide and a behavior with important ecological implications.

ISSN:0706-652X    

DOI:10.1139/f74-243

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The antibiotics vancomycin, penicillin G, novobiocin, and oxytetracycline were examined for in vivo effectiveness against gaffkemia, the fatal bacterial infection of lobsters (genusHomarus) caused byAerococcus viridans(var.)homari(formerlyGaffkya homari). Only vancomycin was truly effective against an established infection and then only when given at high levels (25 mg/kg lobster body weight) in the early stages of infection, prior to development of hemolymph bacterial numbers in excess of 3 × 104/ml or coincident hepatopancreatic bacterial levels of 1 × 107/g. Even massive cumulative doses (500 mg vancomycin/kg body weight), when given after establishment of maximum bacterial numbers, failed to impede the infection. Rates for the clearance of vancomycin from lobsters, established by using three different concentrations (25, 10, and 5 mg/kg body weight, respectively), were extremely slow and markedly concentration dependent. Twenty-five milligrams vancomycin/kg body weight injected prior to infection still gave a high degree of protection against challenge with the pathogen 50 days later in lobsters held at 15 C. One milligram vancomycin/kg body weight administered prior to infection gave complete protection against gaffkemia for 15 days after the antibiotic had been administered.

ISSN:0706-652X    

DOI:10.1139/f74-244

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Commercial mercury-lamp water sterilizers can be used for removal of free chlorine in water supplies, by photochemical action. The efficiency of removal decreases with increasing pH, but is little affected by temperature. It is greatest at low initial chlorine concentration. Equipment with either low or high pressure mercury vapor lamps may be used. Removal of 90% of free chlorine can be effected at about 13.0 liters min−1with a sterilizer using eight low pressure lamps of 40 W, or at 50 liters min−1or more with two 1200-W sterilizers with high pressure lamps in tandem. Treated water appears to be harmless to fish.

ISSN:0706-652X    

DOI:10.1139/f74-245

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Various degrees of resistance to infection of lobstersHomarus americanusbyAerococcus viridans(var.)homari(formerlyGaffkya homari) were induced by vaccines prepared in different ways. Vaccines consisting of formalin-killed cells of a virulent strain of the pathogen (grown in vitro and in vivo) gave a low level of protection, i.e. the vaccinated lobsters were able to resist challenges of 200 bacteria/kg host body weight. A vaccination approach utilizing a low initial dose of the antibiotic, vancomycin, followed 24 h later by injection of 1 × 106live pathogen cells/kg body weight produced a high degree of resistance to subsequent challenge at times considerably beyond the clearance times for the antibiotic. Fatal infections in normal lobsters are readily established with 10 pathogen cells/kg body weight whereas treatment of lobsters with the vancomycin-live pathogen combination resulted in an LD50of 2 × 107live pathogen/kg body weight. It is suggested that the relative effectiveness of the various vaccines is related directly to the concentrations of cellular components within the pathogen, possibly precursors of cell wall mucopeptides.

ISSN:0706-652X    

DOI:10.1139/f74-246

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Rainbow trout (Salmo gairdneri) fed a pyridoxine-deficient diet developed clinical signs of the deficiency after 8 wk of feeding. Erythrocyte and muscle glutamic pyruvic transaminase (GPT) concentrations were significantly depressed in deficient fish, while liver GPT was significantly elevated. Liver GPT was also elevated in starved trout suggesting the increase in enzyme concentrations was secondary to the deficiency. A normocyte, normochromic anemia, which responded favorably to pyridoxine, developed in pyridoxine-deficient trout. Microscopic lesions were found in gastrointestinal tract, kidney, liver, pancreas, and thymus of deficient fish.

ISSN:0706-652X    

DOI:10.1139/f74-247

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Laboratory studies were conducted on eggs from a southern British Columbia population ofHippoglossoides elassodon. Salinity of neutral buoyancy of eggs decreased from about 25% shortly after fertilization to 17–18% at hatching. The incubation period ranged from 20.9 days (2.36–4.0 C) to 7.2 days (10.65 C). At temperatures of 5.5 C or lower and salinities of 19‰ or lower, larvae tended to hatch at a less advanced stage of development. Mean length of newly hatching larvae increased in successive periods throughout the hatching interval. At mean hatching time, larval length varied from 3.2 mm (15‰, 3.0 C) to 6.3 mm (25‰ 6 C). Larvae from eggs incubated over the range of test conditions (10.42–39.58‰, 2.36–10.65 C) reached a length of 6.9–7.2 mm at yolk exhaustion. Hatching success was highest in trials at 25‰, 6 and 7 C; maximum percent viable hatch is predicted at incubation conditions of 29.16‰, 7.38 C. Posthatching larval survival appeared normal at salinities of about 20–37‰ and temperatures of about 5.5 to >10.65 C. Extensive early larval mortality occurred at salinities of 19‰ or less and at temperatures below 5.5 C. Incipient low lethal temperature levels are estimated to be near 3.5–4.0 C for incubating eggs and 4.0–4.5 C for larvae.Egg and larval characteristics of the experimental material were compared with similar data from the literature on North Pacific OceanHippoglossoides. A number of previous distinctions made between eggs and larvae ofH.elassodon,H.robustus, andH.dubiusrequire further validation owing to the possible confounding of genetic and environmental influences on the attributes studied. Distribution and abundance ofH.elassodonover its North American range is discussed on the basis of the evidence gathered.

ISSN:0706-652X    

DOI:10.1139/f74-248

出版商:NRC Research Press    

年代:1974

数据来源: NRC