摘要:

By persistent gill-netting in Cultus lake, British Columbia, the predaceous fish which feed on young sockeye (Oncorhynchus nerka) have been considerably, though unevenly, reduced in numbers. The populations of squawfish and char, of lengths greater than 200 millimetres, were reduced in three years to about 1/10 of their original numbers. The abundance of trout and coho salmon have been much less affected by netting, if at all, though a considerable number have been killed. From the first year of control operations the survival rate of young sockeye salmon was considerably increased. In the three years which have been tested, the mean survival rate has been increased three and a third times over average conditions prior to control. In absolute figures, this represents 3,800,000 migrants saved, which are expected to yield 380,000 adult sockeye. Even disregarding the important cumulative future increase, the immediate return from the work is a quantity of sockeye whose value is many times greater than the cost of control work.

ISSN:0706-652X    

DOI:10.1139/f40-034

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

The scale method of age determination has been used to study rates of growth of the Rocky Mountain whitefish,Prosopium williamsoni(Girard), which vary considerably in different localities, and can be correlated to some extent with altitude or temperature. A curve is given showing the relationship between growth of scale and body. Fast-growing individuals tend to maintain their superiority in growth rate throughout their existence. Slow-growing races live longer and eventually reach a maximum length similar to that of fast-growing fish.

ISSN:0706-652X    

DOI:10.1139/f40-035

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

Percentages of moisture, protein, fat and ash in meat and liquor were determined. Food value of the meat was approximately 100 calories per 100 grams.

ISSN:0706-652X    

DOI:10.1139/f40-036

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

Structural variations in vertebral centra of young Pacific herring are described and classified. Evidence that "abnormal" centra are the result of fusion is brought forward, and the numerical value of complex segments is discussed. It is shown that populations may differ by the frequency with which vertebral irregularities appear, and that such differences may be associated with environmental factors. Fused centra tend to occur most frequently in the region of the twentieth vertebra, and this appears to be associated with differential growth in the vertebral column.

ISSN:0706-652X    

DOI:10.1139/f40-037

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

Among 57 individual oysters (Ostrea virginica) followed from 1932 to 1936, almost every variation occurs from no change in sex to change almost every year. High proportion of unchanging males suggests these as genetically males and the others with apparently random sex determination as hermaphrodites.

ISSN:0706-652X    

DOI:10.1139/f40-038

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

The copepodsEurytemora herdmani,Tortanus discaudatus,Pseudocalanus minutusandCalanus finmarchicusare stimulated to move upward by the decreasing light from the setting sun while they migrate downward by the increasing light from the rising sun. These responses to light govern, in part, their availability as food for the herring.

ISSN:0706-652X    

DOI:10.1139/f40-039

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

In the waters of the Scotian shelf there are: An "upper" layer with temperature in summer above and in winter below 5 °C., and with salinities always less than 32‰; an "intermediate" layer with temperature generally below 5° and with salinities between 32 and 33.5‰; and a "bottom" layer with temperature above 5° and salinities above 33.5‰.From 1934 to 1939, 1934 was the warmest and 1935 the coldest year in these waters. The submarine physiography of the shelf is important in preventing interchange between the deeper waters at the northeast and the remainder.

ISSN:0706-652X    

DOI:10.1139/f40-040

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

The nature of the surface non-tidal circulation in the sea in the approaches to Juan de Fuca strait, latitude 48°30′N., longitude 125°00′W., is interpreted from stream line diagrams, four of which are reproduced. It is shown that the system represents a balance between a wake stream flow from Juan de Fuca strait, which is directly related to the volume of land drainage, and the independent wind-driven currents, which are due to one of the two prevailing coastwise winds in the area.

ISSN:0706-652X    

DOI:10.1139/f40-041

出版商:NRC Research Press    

年代:1941

数据来源: NRC