摘要:

Morphometric and electrophoretic examinations were made of 314 specimens comprising 16 samples of flathead sole (Hippoglossoides) from various locations in the North Pacific. On the basis of muscle and hemoglobin analysis no distinction could be made among samples from different locations. However, with the aid of discriminant function analyses on the morphometrics three groups were distinguishable which can be equated toH.elassodon(Jordon and Gilbert),H.robustus(Gill and Townsend), andH.dubius(Schmidt).

ISSN:0706-652X    

DOI:10.1139/f77-076

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Comparative morphological investigation of extensive series ofPleuroxus denticulatusBirge from North America and Europe revealed considerable variability in certain characters. These are quantitative (body dimensions), qualitative (structure of postabdomen), and meristic (number of ventro–caudal shell denticles). With regard to the postabdomen, two morphotypes, connected by transitional forms, can be distinguished in both sexes, which, however, are not separated geographically. Nevertheless, there are certain field populations (e.g. from Indiana and southern Germany) that are so strongly divergent in certain characters they would satisfy the taxonomic requirements for assigning them to different geographic races. The North American population s are distinguished by having significantly more denticles on the ventro–caudal angle of the valves, the frequency distribution of which satisfied the 75% rule for the separation of subspecies. However, we do not consider the distinctness in this single character of a single west European population sufficient to justify the establishment of two geographic subspecies. Trunk limb morphology, which yields important conclusions concerning the systematic affinities ofPleuroxus denticulatus, is also described. The species, along withPleuroxus truncatus(O. F. Müller) andPleuroxus proauvusBirge, form a group of closely related species, characterized by the sperm ducts opening on the lateral surfaces of the postabdomen and by the relatively small structural differences between the male and female postabdomen. Finally, differentiation of characters within thetruncatusgroup is analyzed in detail.Key words: Cladocera, Chydoridae,Pleuroxus, taxonomy, morphological variation, geographical distribution

ISSN:0706-652X    

DOI:10.1139/f77-077

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The hyperglycemic stress response of fish was evaluated for use as a rapid test for assessing stressful levels of pulpmill effluents (BKME). Plasma glucose levels in juvenile coho salmon (Oncorhynchus kisutch) were elevated within 0.5 h following transfer from the holding tank to aquaria containing either fresh water or BKME, peaking at 3–6 h and returning to near-basal levels at 24 h. Acclimation of coho to aquaria for 24, 48, 72, or 96 h prior to addition of effluent resulted in marked increases in glucose levels attributable to BKME. Significant responses to effluent were found with exposures of 3–10 h, whereas levels were not increased with exposures of 2 h or less. Plasma glucose levels increased progressively with increasing effluent concentrations. Threshold effect (EC50) values varied from 0.04 to 0.16 of the 96-h LC50 values. The response to BKME treated previously by the activated sludge process or by foam separation was diminished or absent altogether.Juvenile rainbow trout (Salmo gairdneri) and coho displayed a hyperglycemic response with 4-, 6-, or 8-h exposure to an identical effluent concentration, although the magnitude of response of rainbow was less in each instance.The extent to which blood sugar levels are elevated due to effluent exposure is directly related to the liver glycogen reserves of the fish. Acclimation to test tanks for 24–48 h followed by exposure for 3–6 h is suggested as the best working combination for this test.

ISSN:0706-652X    

DOI:10.1139/f77-078

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Tolerance of coho salmon (Oncorhynchus kisutch) to nitrite was increased when the concentration of chloride ion in the environment was high. The results of flow-through bioassays revealed that no mortality occurred when yearling coho salmon were subjected to nitrite-nitrogen (NO2−–N) of 29.8 mg/ℓ and chloride (Cl−) of 261.3 mg/ℓ for 48 h. When yearling coho salmon were exposed to 3.8 mg/ℓ NO2−–N and 2.5 mg/ℓ Cl−for 12 h, the resultant mortality was 58.3%. Possibly, chloride competes with nitrite for transport across the gills and integumental tissues, thereby interfering with the onset of nitrite-induced methemoglo

ISSN:0706-652X    

DOI:10.1139/f77-079

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Mercury levels in concentrations similar to those in natural waters contaminated with mercury (0.1 and 1.0 μg/ℓ) caused significant reduction in algal numbers, standing stock, and diversity. Reductions in diversity resulted from a decrease in the evenness of distribution of numbers among species and a decline in the number of species. Although the algal community was affected by mercury ions, the magnitude of change was small at the mercury levels tested and the number of species affected were few. The decline in algal standing crop could indirectly affect other food chain members that possess physiological resistance to the mercury. There was no evidence of direct or indirect impact on the herbivorous or carnivorous midges. The impact on primary producers was not sufficient to be transferred to consumer trophic level

ISSN:0706-652X    

DOI:10.1139/f77-080

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The activity of erythrocyte δ-amino levulinic acid dehydratase (ALA-D) of fish is easily measured under a variety of experimental conditions. Exposure of rainbow trout (Salmo gairdneri), brook trout (Salvelinus fontinalis), goldfish (Carassius auratus), and pumpkinseeds (Lepomis gibbosus) to lead consistently inhibited ALA-D within 2 wks at concentrations as low as 10, 90, 470, and 90 μg/ℓ, respectively. In rainbow and brook trout these concentrations were closely related to the published minimum effective concentrations causing sublethal harm. There was a significant linear relationship between ALA-D activity and log of blood lead concentration, between ALA-D activity and log of lead in water, and between blood lead and lead in water. Near lethal exposures to cadmium, copper, zinc, and mercury did not significantly inhibit ALA-D activity. Recovery of ALA-D activity of rainbow trout after transfer from 120 μg/ℓ lead to clean water occurred in 8 wk. This enzyme provides fast, consistent, specific, and sensitive estimates of lead concentrations causing sublethal harm to fish and may help to relate sources of lead to degree of exposure of fish populations in the field.Key words: lead, sublethal toxicity, fish, indicator enzyme, δ-amino levulinic acid dehydra

ISSN:0706-652X    

DOI:10.1139/f77-081

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Experiments were conducted on young-of-the-year or yearling carp (Cyprinus carpio) to determine the influence of temperature and photoperiod on the growth promoting ability of bovine growth hormone, and the dose–response relationship of bovine growth hormone on carp growth. There was relatively greater enhancement of growth due to bovine growth hormone at an above optimum temperature for growth, 35 °C, than at the optimum temperature, 30 °C. This was possibly due to decreased production or activity of endogenous growth hormone at the higher temperature, resulting in a greater relative response to the exogenous bovine hormone. Inhibition of endogenous growth hormone may be a major limiting factor to growth at above optimum temperatures. Daylengths of 9 and 16 h had no effect on the response of the fish to hormone injections. At a temperature of 35 °C fish receiving bovine hormone dosages of 12.5, 25, 50, and 100 μg/g per wk responded with increasingly greater growth rates over fish receiving sham injections. Condition factors of fish increased throughout most of the experiment with greater increases among hormone injected fish.

ISSN:0706-652X    

DOI:10.1139/f77-082

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Seventy oceanographic sections across Cabot Strait, taken at various times of the year between 1950 and 1974, were utilized to describe the average oceanographic featues, currents, and volume transport patterns as well as their variations with depth and time. The water mass structure in Cabot Strait is a two-layered structure; the water in the upper 50–100 m is typically moving seaward, while below that depth it is commonly found to be moving into the Gulf. The character of the upper layer which is normally not of uniform thickness across the Strait, but is distinctly wedge-shaped, is subject to considerable seasonal variation, whereas that of the lower is quite uniform the year round. Seasonal and long-term variations of the physical properties in Cabot Strait are described.Outflow through Cabot Strait is shown to be concentrated in the upper layer off Cape Breton and is balanced by inflow at intermediate depths on the Newfoundland side and in the deep portions of the section. The maximum and minimum transports, both inflow and outflow, occur in August and June, respectively. The net outward volume transport through the Strait increases from 9 × 103m3/s in April to 25 × 103m3/s in August and decreases to about 0.1 × 103m3/s in February. The weighted mean value, 13 × 103m3/s agrees well with the value obtained from an estimate of net freshwater input rate (run-off plus precipitation minus evaporation) above the section. The maximum transport occurs at times of surface minimum salinity. Horizontal advective transport of salt is found to be more important than horizontal diffusive transport. Recommendations for future transport studies in Cabot Strait are presented.

ISSN:0706-652X    

DOI:10.1139/f77-083

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Effects of temperature shocks from thermal plumes on driftingIsonychia(Ephemeroptera: Baetidae) andHydropsyche(Trichoptera: Hydropsychidae) larvae were examined in a laboratory simulation. Groups of both insects were collected at various seasons and acclimated in the laboratory at temperatures comparable to those in the field. Groups were exposed to thermal shocks of varying duration and observed for periods of 10 days afterward. Consistent statistically significant differences in mortality between treatment and control groups were not evident until shock temperatures neared the respective upper lethal limits for the two insects. While consistent treatment related differences in molting frequency inIsonychiawere not obtained, changes in the patterns of molting were observed. Behavioral tests withIsonychiaindicated no discernable treatment effects on rheotaxis, phototaxis, and substrate orientation. No discernable effects of treatment on susceptibility to predation ofIsonychiabyCottus carolinaewere observed.

ISSN:0706-652X    

DOI:10.1139/f77-084

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Depth profiles of dissolved reactive silicon and amorphous particulate silicon were made at monthly intervals (April–November 1975) at stations along a southwest transect from Grand Haven, Michigan, to a point approximately in the center of the southern basin of Lake Michigan Biological utilization of reactive silicon occurred prior to stratification in late May or early June. A shift from a 100% diatom-dominated phytoplankton community in spring to ~ 12% diatoms in August was attributed to the low dissolved silicon values observed in the surface water (< 2 μmol/ℓ) during summer. The total amount of biologically active silicon (TBAS) for the lake was found to be approximately 19 μmol/ℓ. Winter values were ~ 2 mol/ℓ amorphous silicon and ~ 17 μmol/ℓ reactive silicon. During the period June–August 80% of TBAS had been utilized by the diatom community, with only 20% remaining as reactive silicon. Greater than 50% of TBAS was lost from the water column during spring and early summer, which was attributed to settling of diatom frustules and the sinking of zooplankton fecal pellets containing frustules. This silicon was subsequently returned, in a soluble form, to the deep water during the fall. The amount of TBAS that was recycled was estimated to be 80–100%.Key words: Lake Michigan, diatoms, recycling, dissolution, limitation,

ISSN:0706-652X    

DOI:10.1139/f77-085

出版商:NRC Research Press    

年代:1977

数据来源: NRC