摘要:

A Schumacher population estimate based on 995 maskinonge taken by trap nets, between the months of May and October in the years 1951–1953, set the number of maskinonge in Nogies Creek at between 769 and 1,122 in July 1953. The mean standard length of these fish was 53.0 cm. The rate of growth (26.3 cm. S.L. in the first year) compared favourably with that for maskinonge in other waters. Fish of age-groups II, III and IV predominated. The small number of fish over four years of age was apparently due to a 70% annual mortality rate at least after the third year of life and perhaps before age III.Recaptures of tagged maskinonge demonstrated that there was little movement of maskinonge in summer, and what movement there was, was mainly upstream. In the fall there was far more movement of fish, and this was mainly in a downstream direction.The area supports a fairly large population of maskinonge but the high mortality after three years of age limits its value for raising maskinonge to legal size. The potential for rearing fish to three years of age is such that it may be very advantageous to move hatchery fish here for one or two years before liberation.

ISSN:0706-652X    

DOI:10.1139/f56-039

出版商:NRC Research Press    

年代:1956

数据来源: NRC

摘要:

The great expense of modern fisheries research programs necessitates, prior to data collection, careful consideration of the mathematical model to be used in analysis. The simplest type of model requires little information, but has poor predictive reliability. Progressively more complex models have higher information output, in the form of predictive reliability and insight into dynamics of the exploited population, but require higher information input, not only as amount of data, but array of types of data. The general form of the most complex type of model is derived by consideration of available information on the dynamics of fish populations. The specific form of the component terms and the values of the parameters must be derived in each instance through a combination of deduction and joint regression analysis. To solve the models, catch-effort data must be weighted to avoid gross errors, all readable scales must be aged, regardless of difficulty in interpretation, and various modifications of the theory and practice of tag-recapture programs are necessary. Schooling behaviour and regenerated scale centers influence necessary minimum size of scale sample.

ISSN:0706-652X    

DOI:10.1139/f56-040

出版商:NRC Research Press    

年代:1956

数据来源: NRC

摘要:

Evidence of fluctuations in the strengths of lemon sole year-classes in Hecate Strait has been obtained from analysis of the age composition of the adult stock during a ten year period. These fluctuations are correlated inversely with sea surface temperatures at the time in the life-cycle when the young are in the pelagic stage. Explanation of this relationship is based on evidence that the young are transported by a northward moving current, from a spawning ground somewhere in southern Hecate Strait to a restricted nursery area lying along the northeastern shores of the Queen Charlotte Islands.From the results of laboratory experiments on the effect of temperature on the rate of growth of lemon sole embryos, it is concluded that small annual differences in sea temperature produce marked differences in the duration of the pelagic stage. Hence, in years when temperatures are below average, the larvae are carried for a longer period by the northward moving currents. It is maintained that this results in a greater deposition of young on the nursery ground.

ISSN:0706-652X    

DOI:10.1139/f56-041

出版商:NRC Research Press    

年代:1956

数据来源: NRC

摘要:

Babine Lake and connected Nilkitkwa Lake, a total lake area of 174 square miles, provide nursery facilities for progeny of the largest sockeye salmon run to the Skeena River in northern British Columbia.Based on catch per unit of fishing effort, tow-net collections in August and October, 1955, indicate that at least 67%, and possibly as much as 88%, of the total age 0 sockeye population of these lakes (estimated as 50 to 60 million) was concentrated in Nilkitkwa Lake and the North Arm of Babine Lake: that is, in 11.4% of the total lake area. Mean size of young sockeye in these areas of concentration was much smaller than in the sparsely populated remainder of Babine Lake.This unequal distribution of young sockeye, and resulting inefficient utilization of the lake nursery facilities, is apparently a result of the distribution of the spawning parent population and a limited dispersal of young sockeye from their points of entrance into the lake as fry.

ISSN:0706-652X    

DOI:10.1139/f56-042

出版商:NRC Research Press    

年代:1956

数据来源: NRC

摘要:

Hebron Fjord, extending some 28 miles into the northeast coast of Labrador at about latitude 58° 10′ N., and having a sill at depth of 59 m. across its mouth, was visited at various periods during 1949, 1952 and 1954. The present paper deals with the oceanographic regime and physical environment in the fjord and adjacent coastal waters. Data on tides and currents, and on contributions of fresh water from precipitation run-off and ice melting are given. Oceanographic factors discussed include temperature, salinity, dissolved oxygen, inorganic phosphate, temperature–salinity relationships, and long-term trends. Ice formation as an oceanographic phenomenon is considered. Computations of thermohaline convection are made, and the effects of ice formation and exchange in determining the winter oceanographic structure are discussed. Above sill depth exchange occurs principally by horizontal movements and a flushing time of about 68 days is computed. Below sill depth exchange must involve vertical movements and occurs principally by convection in winter. Calculations of the A factors of eddy conductivity and eddy diffusivity are made. Dynamic computations of water transport are given. During winter a water temperature of −1.75 °C. exists at all levels in the fjord, rising in summer only to −1.68° at 250 m. and −1.00° at 100 m., causing the bottom waters to remain an isolated pocket of high Arctic environment during the summer and fall seasons as contrasted with the disappearance of negative temperatures down to 120 m. by mid-October outside the fjord. Inorganic phosphate increases with depth; photosynthesis maintains oxygen at super-saturation above 30 m. during summer, and the rate of oxygen consumption and renewal by vertical transport below 80 m. is calculated.

ISSN:0706-652X    

DOI:10.1139/f56-043

出版商:NRC Research Press    

年代:1956

数据来源: NRC