摘要:

Population estimates of an unexploited brook trout population at Matamek Lake, Quebec, indicated that more than 86% of the total population inhabited the tributaries of the lake during the summer of 1968. As opposed to the stream habitat, the combination stream–lake ecosystem moderated the mortality rates of the intermediate age-groups and allowed survival to higher ages in the population. Estimates of standing stock and production in the lake were 3.1 and 2.2 kg/ha respectively during 1968.The population was characterized by a slower growth rate, higher age at maturity, higher survival rate in the intermediate age-groups, and longer life span when compared with an exploited population in Wisconsin. Increased numbers of trout in higher age-groups at Matamek Lake were attributed to high survival rates in the intermediate age-groups in the absence of exploitation. Low estimates of standing stock and production were attributed to environmental factors affecting growth.

ISSN:0706-652X    

DOI:10.1139/f70-051

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Differences in chemical composition in 1965–67 between two lakes contaminated by uranium-milling wastes and one unaffected lake were related directly to the nature of processes in uranium extraction and subsequent waste treatment. LowpH and high concentrations of SO4−2, NO3−1, and Ca+2occurred in the contaminated lakes. Low concentrations of inorganic carbon, which apparently limited production in the contaminated waters, resulted from reduced solubility, loss, and possibly inefficient regeneration of CO2. Other major nutrients did not appear to be limiting, since nitrates were in greater supply in the contaminated lakes than in the unaffected lake and phosphorus and silica occurred in similar concentrations in all three lakes.Lower phytoplankton populations and lower indices of diversity were found in the contaminated lakes than in the unaffected one. Many species of Bacillariophyceae, Chrysophyceae, and Myxophyceae developed in the unaffected lake but were absent or occurred in extremely low numbers in the contaminated lakes.Average primary productivities were approximately 70 and 30 mg C m−2day−1in the two contaminated lakes and 130 mg C m−2day−1in the unaffected lake. In situ areal and volumetric measurements in laboratory and field bioassays confirmed the importance of inorganic carbon in limiting primary productivity. A potential compensatory mechanism in the contaminated lakes was a deepening of the euphotic zone. Although greater concentrations of inorganic carbon occurred and were assimilated in hypolimnetic than in epilimnetic waters, the mechanism was not sufficient to overcome the effects of reduction in both species diversity and abundance of phytoplankton on the areal primary productivity.

ISSN:0706-652X    

DOI:10.1139/f70-052

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Distribution of walleye (Stizostedion vitreum vitreum) larvae in Oneida Lake was followed in 1960–67 from the time 200 million 1- to 3-day-old hatchery larvae were stocked until dispersal was complete 10–15 days later. The distribution of prolarvae indicated a high proportion of the population originated from stocking. Newly stocked larvae concentrated near bottom and were transported by bottom currents into the western third of the lake. Older larvae were most abundant near the surface after yolk absorption and they were transported east by surface currents generated by the predominantly westerly winds. Distribution of larvae 8–9 days after release in 1966 and 1967 was similar to the distribution predicted from water current and wind velocity data. Larvae were dispersed further east in 1967, when winds were strong, than in 1966, when wind velocity was low.

ISSN:0706-652X    

DOI:10.1139/f70-053

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Seventeen specimens ofLepidion eques(Günther) taken by the Fisheries Research Board of Canada St. John's, Nfld., Biological Station are apparently the first records of the species from the western Atlantic west of West Greenland. Comparison with specimens from the northeast Atlantic shows some differences in averages of meristic and morphometric characters, but with overlapping ranges in these characters.Comparison of these North AtlanticL.equeswith the MediterraneanLepidion lepidion(Risso) revealed that although closely related, these species are separable on the bases of the smaller orbit diameter in relation to the head length and especially by the relatively larger postorbital length inL.lepidion.Lepidion guentheri(Giglioli) is distinctly different from these two species in some meristic and many morphometric characters. Lectotypes ofL.equesandL.guentheriare designated. Various incorrect or doubtful records ofLepidionare discussed. Two giant lepidions reported recently from the northeast Atlantic asL.guentheriare tentatively assigned toLepidion schmidtiSvetovidov, a species hitherto known only from Japan.The distributions of the North Atlantic species ofLepidionare discussed and information is provided on sexual maturity.

ISSN:0706-652X    

DOI:10.1139/f70-054

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Two records ofAnotopterus pharaoZugmayer from the Labrador Shelf, and three from the Grand Bank and vicinity, are the only records of captures from these areas and the only ones from the Newfoundland area apart from four Soviet records from Flemish Cap. One of the Grand Bank captures, October 1952, and a Labrador capture, September 1954, are the earliest records from the Newfoundland area.Meristic and morphometric data indicate that these Newfoundland area specimens and two other west Greenland and one southeast Greenland specimens ofAnotopterusexamined by me are referable toAnotopterus pharaoZugmayer, as are all known specimens from the eastern Atlantic, and are similarly specifically related to Pacific and antarctic specimens. However, a few differences will need to be resolved by studying a larger number and size range of specimens from all areas of distribution.

ISSN:0706-652X    

DOI:10.1139/f70-055

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The fatty acid compositions of phospholipids and triglycerides from two lots ofMeganyctiphanes norvegica(M. Sars), and of total lipids of two additional lots of different origin, showed characteristics commonly found in lipids of carnivorous higher animals such as herring. The fatty acids in both phospholipids and triglycerides of one sample ofThysanoëssa inermis(Krøyer), although qualitatively similar to those of theM.norvegicalipids, showed a closer quantitative relationship to phytoplankter fatty acids and suggested that this species is herbivorous. These observations are discussed in terms of biological data on the feeding habits of the animals, and their basic biochemical processes as related to overwintering or other times of food scarcity. The crustacean samples, obtained from the stomachs of fin whales captured off Nova Scotia, had 1.2–2.4% total lipid, with nonsaponifiable materials accounting for 3–5% of the lipids inM.norvegicaand 10% inT.inermis. The potential utilization of these species in artificial rearing of trout or salmon is discussed.

ISSN:0706-652X    

DOI:10.1139/f70-056

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A system is described for continuously recording density changes across a population of benthic organisms from a submersible. This system was tested in the Northumberland Strait over a population of scallops (Placopecten magellanicus). A continuous record of scallops visible from the viewport of the submersible was registered on a chart recorder, concurrently with a series of exposures by an externally mounted automatic camera. Transects up to 4 km long were completed in a single dive.A distance trace provided by a towed odometer wheel allowed visual counts to be expressed as linear densities (numbers seen per unit distance travelled) independently of submersible speed. An estimate of the width of visual field at a known height off bottom enabled linear densities to be converted into population densities (numbers seen per unit area of sea floor).Scallop distribution in the area was markedly contagious. Areas of high scallop density (up to 4.8 scallops/m2), of the order of 0.5 km across, on sand, were separated by stretches of mud where scallop density was below 0.1/m2.

ISSN:0706-652X    

DOI:10.1139/f70-057

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Unanesthetized specimens of Pacific dogfish,Squalus suckleyi, were used to study the relationships of oxygen uptake to ventilation and blood perfusion of the gills. Ventilation–perfusion ratioswere determined over a wide range.In resting dogfish theratios normally fell within the range of 10–20 at 6–10 C with a ventilation usually between 200 and 500 ml/min∙kg and a cardiac output between 20 and 40 ml/min∙kg. The extraction of oxygen from water varied from about 20 to 50% within thatrange, but at lower ratios the extraction was higher and sometimes exceeded 75%. When extraction was high the oxygen tension of expired water often fell below that of arterial blood thus indicating countercurrent gas exchange.The oxygen uptake varied almost directly with cardiac output over a wide range and with ventilation at low and normal water flows.Data are presented regarding the effectiveness of oxygen removal from water, oxygen uptake by blood, and overall transfer of oxygen from water to blood at various ventilations.In curarized dogfish the heart rate varied with changes of induced ventilation. The reflex nature of this cardiac and ventilatory coupling was revealed by its abolition when the fish were atropini

ISSN:0706-652X    

DOI:10.1139/f70-058

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Past and current researches relating to olfactory acuity and discrimination in fishes, with special reference to homing salmon, are reviewed.When the nasal sac of spawning Pacific salmon is stimulated with water from the spawning site a high amplitude electroencephalographic response of characteristic pattern is recorded from the olfactory bulb. This electrical response is specific in the sense that it cannot be evoked by water from spawning sites of other groups of breeding salmon. Further, the salmon respond clearly to water taken from places along their migratory routes below the spawning sites. These findings suggest that olfaction is an important factor in guidance during the final phases of homeward migration of salmon. It is also possible that salmon retrace sequentially a trail of stimuli that is the reverse of thatimprintedin the young fish on their seaward migration.Although the available data do not delineate the sensitive period, or the duration of the imprinting process, there is accumulating evidence that only a short period is necessary for imprinting, which may occur when the smolts are in their freshwater life.Recent study on the effect of antimetabolites (puromycin, actinomycin D, or cycloheximide) on olfactory bulbar discrimination in homing salmon suggests that long-term olfactory memory in these fish depends upon continued metabolism of RNA and continued protein synthesis. The possibility that the imprinting process in young fish may be affected by polluted water, which has recently become a serious problem in fisheries, is discussed. The need for electrophysiological as well as biochemical studies at a macromolecular level of the imprinting process is emphasized.Finally, the hypothesis is discussed that a home stream odour may act most effectively as a simple "sign stimulus," which, through the release of a positive rheotropic response, induces the fish to move upstream toward home. This is largely based on the recent experimental observations of the orientation mechanism in several species of teleost fishes.

ISSN:0706-652X    

DOI:10.1139/f70-059

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Widespread atresia in northern pike ovaries was associated with low year-class abundance in three successive years, 1966–68, in Lake Oahe and Lake Sharpe, South Dakota, two large Missouri River impoundments. Atresia was associated with fluctuations in water temperature and level that apparently interrupted spawning.

ISSN:0706-652X    

DOI:10.1139/f70-060

出版商:NRC Research Press    

年代:1970

数据来源: NRC