摘要:

Juvenile coho salmon (Oncorhynchus kisutch) of three transferrin genotypes (AA,AC, andCC) were experimentally infected with the causative agent of bacterial kidney disease (BKD) and mortalities observed. Six experimental and control groups were used: 1) bacteria-infected + no Fe+3; 2) bacteria-infected + low Fe+3levels; 3) bacteria-infected + high Fe+3levels; 4) saline control; 5) high Fe+3control; and 6) low Fe+3control. In all experimental groups, theAAgenotype was the most susceptible to BKD and theCCgenotype the most resistant. Addition of exogenous iron did not appear to increase the pathogenicity of the disease. Distribution and uptake of radioiron (59Fe) in control and BKD-infected fish was studied. BKD-infected fish were found to have consistently higher levels of59Fe in whole blood, plasma, and liver than control fish. In control and experimental fish, spleen, head kidney, and liver tissues were found to accumulate59Fe, while white muscle and gall bladder tissues did not. The effect of BKD on certain hematological characteristics also was determined. Hemoglobin, packed cell volume, total plasma protein, plasma iron, and plasma corticoid levels all may have decreased with the progression of BKD.

ISSN:0706-652X    

DOI:10.1139/f77-001

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Two-year-old rainbow trout (Salmo gairdneri), reared for 2 yr in water containing about 0.00025 mg/ℓ hexavalent chromium (Cr+6) (Naches trout) or between 0.002 and 0.010 mg/ℓCr+6(Hanford trout) accumulated appreciable chromium, yielding whole body residues of about 0.029 and 0.18 μg/g wet tissue, respectively. Highest concentrations were in the opercular bone, spleen, kidney, gastrointestinal tract, and gall bladder. Short-term exposure of Hanford trout to 2.5 mg/ℓCr+6caused a rapid additional increase of tissue chromium, but at 22 days whole body levels were only 0.87 μg/g. Upon return of exposed fish to water containing 0.002–0.010 mg/ℓ chromium, the metal was rapidly depleted from most tissues except kidney, liver, gill, gall bladder, and bile. Chromium accumulated in tissues of trout exposed to 2.5 mg/ℓ Cr+6was not distributed proportionally among the various subcellular fractions but concentrated in the cell cytosol, especially in the liver and gill.Mitochondrial cytochrome oxidase, NADH-cytochrome c reductase, and succinate cytochrome c reductase activities in liver, kidney, gill, and brain tissues of Naches trout, Hanford trout, and Hanford trout exposed to 2.5 mg/ℓ Cr+6were not significantly different except for kidney NADH-cytochrome c reductase which was lower in Hanford and chromium treated fish. Microsomal nitroreductase,O-demethylase and NADPH-cytochrome c reductase and the soluble glucose-6-phosphate dehydrogenase activities in liver and kidney from Hanford trout were significantly lower than those of Naches trout. Exposure of Hanford trout to 2.5 mg/ℓ Cr+6, however, did not reduce the activities of these enzymes below control levels. In vitro studies showed that trout enzymes were fairly insensitive to Cr+6inhibition. These results suggest that observed differences in enzyme activity between Naches and Hanford trout may be caused by factors other than chromium content

ISSN:0706-652X    

DOI:10.1139/f77-002

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

In an investigation of catches of 17 commercial marine species of fish and shellfish from the Gulf of Maine, 10 showed statistically significant correlations with sea temperatures at St. Andrews, N.B., or Boothbay Harbour, Maine. Most fish records contained at least 40 yr of data. Descriptive equations are produced for four species based first on the correlation between catch and sea temperature and second on the correlation between catch and sea temperature allowing for fishing effort. Inclusion of fishing effort, not surprisingly, improved the correlations for all of the species so examined. The equations permitted the "prediction" of later parts of the records from earlier parts.Considering the fish species collectively, the Gulf of Maine system from 1940 to 1959 appeared to be in equilibrium with little fluctuation in the total commercial biomass. We interpret the large fluctuations in individual species abundance as resulting from a combination of fishing pressure and to a significant degree oceanic climate as represented by sea temperature. The small fluctuations in the total biomass displays the species variation, with their differing climatic "preferences," as well as possible predator (including man)–prey relationships. Environmentally imposed patterns underlie at least 50% of the fluctuations in catch of many species and the understanding of these fluctuations is basic to effective management.

ISSN:0706-652X    

DOI:10.1139/f77-003

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Atlantic salmon (Salmo salar) eggs and alevins were raised under conditions where the temperature was systematically varied either at fertilization, at the eyed egg stage, or at hatching. Mortality was more than 20% in eggs started immediately after fertilization at constant incubation temperatures < 4 °C as compared with 5% or less at temperatures > 4 °C. Alevins that eyed at 8 °C and higher were progressively smaller the higher the temperature. The optimum temperature from fertilization to eye pigmentation was near 6 °C. Eyed eggs reared at lower temperatures until hatching were larger than those hatched at higher temperatures. This size differential was maintained until the yolk was completely absorbed at all posthatching temperatures investigated. Sudden decreases in temperature at the eyed egg and hatching stages induced severe edema of the alevin yolk sac, resulting in slower growth and increased mortality.

ISSN:0706-652X    

DOI:10.1139/f77-004

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Ages of spiny dogfish (Squalus acanthias) in the Strait of Georgia, B.C., have been estimated by an X-ray spectrometric technique which involves measuring variations in the element composition within vertebrae.

ISSN:0706-652X    

DOI:10.1139/f77-005

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The interests of many groups, some with multiple objectives, are important to include in evaluating strategies affecting salmon in the Skeena River. A multiattribute utility model is proposed for addressing these issues. Two first-cut utility functions are assessed using the preferences of two individuals familiar with the problem. These utility functions provide a basis for constructive discussion to arrive at a reasonable utility function for examining alternative policies. Two unique features of this study are the explicit focus on value tradeoffs and equity considerations among interest groups, and a comparative examination of the two first-cut multiattribute utility models. This examination indicates the range of fundamental preferences which can be captured using multiattribute utility functions and illustrates the potential of the theory for conflict illumination and resolution.

ISSN:0706-652X    

DOI:10.1139/f77-006

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

In this paper we describe the use of a specific decision analysis tool, multiattribute utility analysis, to investigate conflicting goals in the management of salmon on the Skeena River. We used this technique to determine the preferences of 10 individuals representing several interest groups and different management agencies. It is shown how individuals differ in their preferences, how conflicts can be identified, and how decision analysis can be used to refine an individual's understanding of his preferences. Individuals assessed possible outcomes of different alternative enhancement proposals using two techniques, the decision analysis technique and an intuitive approach. These two methods produced different results. The use of these techniques in the management process is discussed.

ISSN:0706-652X    

DOI:10.1139/f77-007

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Predator–prey interactions between swimming animals of the zooplankton are studied in a mathematical model. The assumptions are: 1) the animals are points in a 1-m3homogeneous space, 2) the animals move at random and are randomly distributed, and 3) the predator animal has an encounter radius given by its sensory system. The mathematics of encounter probabilities are developed for a 3-dimensional space. The results show two optimal strategies: 1) cruising predators which prey upon slow moving animals (herbivores), and 2) ambush (nonmoving) predators which prey upon fast cruising prey. Of the variables used (population densities, speeds of the two animal species, and encounter radius) the encounter radius has the greatest influence on the encounter probabilities. The results suggest a simple community structure and point to the importance of studies on live zooplankton.

ISSN:0706-652X    

DOI:10.1139/f77-008

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

During the first 2 wk of incubation, the pattern of change in DNA concentration tended to precede similar changes in RNA concentration. Unfertilized eggs contained 23.2 and 77.2 μg of DNA and RNA, respectively. DNA concentration rose from 155.8 μg/fry (after 23 days of incubation) to 326.6 μg/larva (14 days after hatching), while RNA increased from 238.8 to 693.3 μg during the same period. Protein per ontogenetic unit was relatively constant during the prehatching stages but dropped markedly just prior to hatching. Of the protein in the unfertilized egg, approximately 20% was retained in the fry at hatching and approximately 50% was retained in the larva following yolk absorption. Total free amino acid concentrations declined just after fertilization, indicating the initiation of protein synthesis or a decline in yolk protein degradation. These concentrations increased to near initial values in the blastula and were nearly doubled in the yolk plus fry at hatching.

ISSN:0706-652X    

DOI:10.1139/f77-009

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

An effect of the lipid pool size on the accumulation and clearance ofcis- andtrans-chlordane by northern redhorse suckers (Moxostoma macrolepidotum) has been demonstrated. A technique was developed using203Hg-labeled methylmercury as a tracer, which permits the direct determination of the assimilation efficiency from food and the biological half-life of chlorinated hydrocarbons in terms of individual fish. Tissue retention of the insecticide chlordane in fish was directly proportional to the adiposity of the fish. For a fish containing 2% lipid, the half-life of thecis-isomer was 60 days and for thetrans-isomer, 33 days. The net assimilation efficiency from food to fish tissue was also influenced by adiposity. These results on uptake and clearance, when used in a simple model for pollutant bioaccumulation, indicate that the steady state concentration of chlordane in fish will not exceed the concentration of chlordane in the diet unless the adiposity of the fish is high.

ISSN:0706-652X    

DOI:10.1139/f77-010

出版商:NRC Research Press    

年代:1977

数据来源: NRC