摘要:

At the time of first filling of Laurel Creek Reservoir in the spring of 1967 the benthic fauna consisted of submerged terrestrial organisms and obligate and facultative rheophilic species. Two months after initial filling substantial populations of colonizing limnophilic species developed in the habitat whereas the terrestrial and obligate rheophilic components were lost. By the 4th month the fauna was dominated by euryoxybiontic limnophiles and by facultative species. In the period immediately prior to reservoir drainage in the autumn of 1967 the population densities of the euryoxybiontic chironomids declined whereas polyoxybiontic species continued to increase in abundance. These changes in the dominance hierarchy of the chironomid fauna were associated with the partial loss of the rich deposits of organic debris by siltation and decomposition. Survival of winter drainage of the reservoir by many limnophilic species produced an appreciably different pattern of colonization when the reservoir refilled in 1968. During the second summer of the reservoir's existence most euryoxybiontic chironomids further declined in abundance and were replaced by polyoxybiontic forms as the dominant species. The facultative species originally derived from the creek fauna are adapted to a wide range of environmental conditions and the modifications of the reservoir habitat with time had little effect on their abundance.

ISSN:0706-652X    

DOI:10.1139/f70-030

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Limnological investigations of an alpine and a lower subalpine lake in Banff National Park from 1966 to 1968 showed that vernal circulation may not extend to the bottom in either lake and that complete autumn circulation may persist for several weeks in both lakes. Winter heat incomes were similar in the lakes, but the summer heat income was much lower for the alpine lake due to heat lost through water renewal. Thermal stratification was more clearly defined in the subalpine lake each year than in the alpine lake. When well-defined chemical stratification occurred, it was short-lived in both lakes. With the exception of phosphate, which was highest in spring and early summer, most changes in chemical composition appeared related to dilution. Very low oxygen concentrations occurred in the bottom water strata of the subalpine lake, but depletion was never severe in the alpine lake. Of the incident visible light 16% penetrated ice and snow cover (1 m) on the alpine lake, but less light reached the water of the lower subalpine lake because of cloudy ice and deeper snow. The trophogenic zone extended to the bottoms of both lakes (about 13 m) for at least part of each year.

ISSN:0706-652X    

DOI:10.1139/f70-031

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The total fatty acids of a natural bloom ofHalosphaera viridishave been determined. A readily extractable lipid fraction, mostly triglyceride, showed additional monoethylenic fatty acid isomers not obvious in the total lipid. Comparisons are made on the usefulness of this data in distinguishing Chlorophyceae and Prasinophyceae within the Chlorophyta.

ISSN:0706-652X    

DOI:10.1139/f70-032

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Mortalities of lobsters held in the laboratory and tagged with sphyrion tags inserted dorsally between the carapace and abdomen (subcarapace tag) and between the second and third abdominal segments (abdomen tag) did not differ significantly. Premoult tag loss was negligible. The subcarapace tag was retained significantly better through moulting.Returns of subcarapace-tagged and abdomen-tagged lobsters released on the fishing grounds in June, 11 weeks before the August 10 opening of the fishing season, were lower than returns of carapace-tagged lobsters released in early August. More subcarapace-tagged than abdomen-tagged lobsters were returned, and a higher proportion had moulted. Growth was comparable to that reported in the literature. Few lobsters were recaptured during the following fishing season, 14–16 months after liberation, and none subsequently. Returns from lobsters less than 63.5 mm carapace length (sublegal) when tagged were extremely low. Poor survival may be related in part to time of release. Some injury to internal organs may occur with both tags. The subcarapace tag is clearly superior but may be of limited value in the field for lobsters below 63.5 mm carapace length.

ISSN:0706-652X    

DOI:10.1139/f70-033

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Studies were performed to determine if increasing water temperatures could control infectious hematopoietic necrosis virus (IHN) disease in sockeye salmon (Oncorhynchus nerka). Mortalities could be prevented if the water temperature was raised to at least 18 C within the first 24 hr after infection of the fish and if the fish were maintained at this temperature for 4–6 days. The disease did not recur after the elevated temperature treatment, but the fish would still contract the disease if they were reinfected. Reasons for the protecting action are discussed.

ISSN:0706-652X    

DOI:10.1139/f70-034

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The three-dimensional distribution ofTriaenophorusinfection in the whitefish (Coregonus clupeaformis) body and the ultrasonic echos received from the parasite cysts are studied in relation to the problem of detecting the parasites with ultrasound. It is shown that ultrasonic scanning of only 15% of the total surface area of a whitefish is required to illuminate (on the average) 70% of the total number of cysts in the body. As a result the search effort required for effective ultrasonic parasite detection can be greatly reduced. A considerably larger ratio of infection (3:2) for the right and left sides of the body is observed than has been previously reported. It is also shown that in the epaxial muscles a parasite is much more likely to be encysted near the surface than deep inside the flesh. Measurements of the ultrasonic cyst-echo durations yielded a distribution with two peaks of different amplitudes indicating a preponderance of spindle-shaped cysts as is actually observed. A negligible percentage of the echos in the distribution are less than 2 μsec in duration; the median width is 6.4 μsec. An outline is given of how these findings can be used to reduce the error rate in an automatic detection system. The paper concludes with a brief discussion of the effects of the transducer aperture on the latter distribution.

ISSN:0706-652X    

DOI:10.1139/f70-035

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The use of a high frequency echo sounder and a midwater trawl in Babine Lake, British Columbia, in 1967 revealed a precise diel vertical movement of underyearling sockeye salmon. From early July to September, from about 1.5 hr after sunrise to 1.5 hr before sunset, the young sockeye were in two distinct layers at about 20 and 35 m, each layer about 6 m thick. About 1.5 hr before sunset the two layers began to ascend. About 0.5 hr after sunset all fish were within 3 m of the surface, and during darkness they were dispersed throughout the top 5–15 m with most fish being below the thermocline. Soon after the first light of dawn the fish usually tended to move toward the lake surface and then descended rapidly to the daytime depths.By early October the pattern had changed markedly. During daylight the fish were still found in roughly two layers at about 24 and 40 m. However, the evening ascent did not commence until about 0.5 hr before sunset, the ascent was much slower, and the fish did not come to the surface but were dispersed between 9 and 27 m. This change in behaviour was temporally associated with a cooling of the epilimnion and a decrease in intensity of feeding.Although the zooplankton of Babine Lake is composed of eight major species, onlyBosmina coregoniand the calanoid copepodHeterocope septentrionalisdisplayed pronounced diel vertical movements. The former inhabited the surface waters during the day and were found in maximum abundance at 12–21 m at night. The latter was found at 21–30 m during the day and the surface waters at night. The major part of the zooplankton standing stock was found above 9 m.Young sockeye fed most intensively in the evening as they approached the surface and again at dawn just as they commenced the descent. At those times the most common food item wasDaphnia longispina, followed byB.coregoniandH.septentrionalis. These three species were strongly selected by young sockeye, since they were numerically much less abundant than other limnetic zooplankton species. In August, terrestrial insects were occasionally of major importance. At midday the upper layer of sockeye (about 20 m) was feeding onH.septentrionaliswhereas the lower layer (about 35 m) was not feeding or was feeding at a low intensity.The double layer of young sockeye during daylight occurred at least in the North Arm of Babine Lake and may be related to feeding. In July and August the fish in the upper layer had less food in the pyloric section of the stomach from 0900 to 1300 hr than did fish in the lower layer, whereas the volumes of food were similar in the two layers by late afternoon. Fish in the upper layer had much more freshH.septentrionalisin the cardiac section from 1200 to 1800 hr than did fish in the lower layer. The ecological significance of the diel vertical movement is discussed briefly.

ISSN:0706-652X    

DOI:10.1139/f70-036

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

This report describes a method of marking living organisms. As an illustration of the method, foreign chemical elements are incorporated into small salmon and the analytical technique of X-ray fluorescence spectroscopy is used to detect and measure minute quantities in the tissues. Mixtures of elements, either in equal or varying concentration, are used to generate a code. Decoding is readily accomplished by irradiating the tagged organisms and monitoring the X-ray fluorescence produced. A large number of unique combinations appear possible using the method as described. Mixtures of chemical elements (atomic numbers 37–69) were suspended in silicone rubber and injected directly into fish tissue. In this manner tags 1 mm2in area were incorporated in the tissue and decoded by nondestructive analysis.

ISSN:0706-652X    

DOI:10.1139/f70-037

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Brook trout were conditioned in about 30 trials to exhibit the propeller-tail reflex, with electric shock as the unconditioned stimulus and light as the conditioning stimulus. When the trout were exposed for 24 hr to sublethal DDT (20 ppb), more than half could not be conditioned at all; the remainder required significantly more trials than did the untreated ones. Three to four weeks after initial testing, the DDT effect had largely disappeared. It seemed likely that the DDT was acting upon central nervous system structures. The general ecological implications of the results are discussed.

ISSN:0706-652X    

DOI:10.1139/f70-038

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The effects of low (0.05 M) and high (0.5–1.0 M) concentrations of glycerol on the growth of 18 species of marine phytoplankters belonging to 7 algal classes were studied. The algae were grown in axenic culture in sea water enriched with nitrate, orthophosphate, silicate, trace-metal ions, vitamin B12, thiamine, biotin, and buffered atpH 7.6–7.8. Apart from a chrysomonad (Prymnesium parvum) and a cryptomonad (Chroomonas salina), none of the species showed any significant growth on glycerol in the absence of light. However, in the presence of light, glycerol enhanced the growth of 16 species, in particular members of the Chrysophyceae and Cryptophyceae, one diatom (Phaeodactylum tricornutum), one rhodophyte (Porphyridium cruentum), and one chlorophyte (Nannochloris oculata). A high concentration of glycerol was required for inducing or asserting growth enhancement of certain species, but was equally effective as the low concentration or was inhibitory to other species. The enhancement effect was observed in the growth rate and in the peak population density, which in many instances was several times that from nonglycerinated cultures and suggested photoheterotrophic growth. Some species showed obvious cytological and metabolic changes from growth on glycerol. The ecological implications of glycerol pollution of sea water are discussed.

ISSN:0706-652X    

DOI:10.1139/f70-039

出版商:NRC Research Press    

年代:1970

数据来源: NRC