摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f58-041

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f58-042

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f58-043

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

A summary of the species of Polychaeta hitherto recorded from the western Canadian Arctic is given. Each of the species enumerated is considered in the light of its known, or unknown, occurrence in each of two regions to the west (northern Alaska and the Chukchee Sea) and two to the east (Hudson Bay and Greenland) respectively. The results show an almost complete balance in the number of occurrences of like species in the regions in both directions, suggesting circumpolar distribution within the area studied.

ISSN:0706-652X    

DOI:10.1139/f58-044

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Recent efforts to establish Pacific salmon in Hudson Bay posed the question of low temperature tolerance in these species. A series of lethal temperature tests at −0.5, −1.0 and −1.5 °C. demonstrated that resistance to temperatures slightly below 0 °C. was limited. Freezing of the blood and aqueous humour occurred at temperatures of −1.0 and −1.5 °C.

ISSN:0706-652X    

DOI:10.1139/f58-045

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The general structure of the Pacific salmon retina is described. Rods, single cones and twin cones constitute the visual cell layer which, together with the dense pigment layer, undergoes photomechanical changes common to most teleosts. Stages in the contraction and expansion of rods and cones, and the migration of pigments are depicted.In the laboratory, cultured sockeye salmon became well light-adapted in 20–25 minutes, whereas the time for dark-adaptation was of the order of 55–60 minutes.In the Lakelse River, a sample of natural-run sockeye and coho smolts was found to be fully dark-adapted by about 10:00P.M. when the light intensity at the water surface was 0.03 foot-candle. Pink and chum fry from Hooknose Creek were similarly dark-adapted by about 9:45P.M. on an evening when the intensity had fallen below 0.002 ft.-c. At the start of evening migration retinal dark-adaptation in sockeye smolts had just started, whereas in pink and chum fry the retina was approximately half dark-adapted when migration commenced.

ISSN:0706-652X    

DOI:10.1139/f58-046

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Strap tags on the operculum of lingcod were recovered almost as frequently as celluloid rings around the upper jaw during their first year at large, but they were retaken much less frequently than celluloid tags in later years; after two years the rate of decrease in return of the two types of tags was about the same. For 1944–47, approximately, the total instantaneous rate of disappearance of tags from fish in the size range 66–90 cm. (56–85 cm. or ages 3–8 when tagged) was 0.46 for a combined calculation, and 0.43 as an average for individual calculations; corresponding apparent survival rates are 63% and 65%. Larger fish have a somewhat larger mortality rate; for smaller fish mortality cannot be measured because they are incompletely recruited. A survival rate for age 6–7, estimated from age and length composition, pertains to an earlier period (1935–40) and is somewhat larger (0.70). For the central range of sizes, instantaneous rate of fishing (1944–47) is estimated to lie between 0.15 and about 0.22, and instantaneous rate of natural mortality between 0.28 and 0.18, depending on what allowance should be made for non-return of tags and wandering of tagged fish. Graphs of yield against rate of fishing and minimum size limit indicate that the present limit (58 cm., 3 lb. dressed) permits greatest yield per age 1 recruit from the present rate of fishing. Increasing the rate of fishing, even when the size limit is adjusted to the best corresponding value, results in relatively small increases in equilibrium yield per age 1 recruit, and a relatively rapid decrease in yield per unit of effort.

ISSN:0706-652X    

DOI:10.1139/f58-047

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Twenty-five thousand drift bottles have been released in lots of one thousand at Ocean Weather Station PAPA and at eleven selected positions in the northeast Pacific Ocean. To April 15, 1958, there have been 816 returns.The principal characteristics of the surface movement, as shown by the drift bottle paths, are in agreement with the geopotential topography, allowing for a component of movement generally to the right across the isobars. The drift bottle results substantiate the seasonal changes in surface movement implied by the geopotential topography. They also show the changes that occur between the periods of the oceanographic surveys.Frequency distribution curves, used to determine the "most probable time at sea" of the drift bottles were similar for all releases.The "most probable speeds" varied between 3 and 9 miles per day and are comparable to average speeds calculated from the geopotential topography.

ISSN:0706-652X    

DOI:10.1139/f58-048

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The Rivers Inlet sockeye catch has averaged about 1 million fish per year, over 45 years. These are from smolts produced in a cold, deep lake, only 30 square miles in extent, and most of it heavily silted by glacial tributaries. The water has only a moderate lime content and its reaction is neutral or very slightly acid. The lake's plankton crops are small, though blooms of bluegreen algae occur in autumn in the clear uppermost basins, following on the death of large numbers of spawning sockeye. Smolts are unusually small in size, averaging about 2 grams when sampled in 1914–16 and again in 1954; almost all are age 1. The commercial gill-net fishery harvests most efficiently the salmon of intermediate sizes: the medium and large age 4 fish, and the medium and small age 5 fish. Hence escapement tends to consist of extremes of size, the larger age 5's, smaller age 4's, and almost all the age 3's. Sockeye spawning takes place in many inlet streams, along parts of the lake shore, and in the outlet river. The spawners in the various tributaries differ considerably in respect to the age structure of their runs, and to some extent in size at a given age, though the selective fishery may account for some part of these differences. Conditions for spawning and incubation in the region are still practically in their natural state.The most important management problem is to determine whether increasing the fry output into the lake would increase or decrease production of adult sockeye: the smolts are now so small that any larger numbersmightpossibly reduce their size below some critical level. Next in importance is to determine whether or not the present numbers of spawners are necessary to fertilize the lake for the growth of the young, and if so, whether a less valuable fertilizer might be substituted.

ISSN:0706-652X    

DOI:10.1139/f58-049

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The "index of return" (ratio of offspring catch to parent catch) was used to compare annual survival among several stocks of British Columbia salmon. Over a period of almost 30 years the major stocks of pink salmon in the Province, excepting those of the Fraser River, exhibited quite similar annual variations in survival. The Fraser River stock behaved somewhat independently of the other stocks. There are indications that among pink salmon early ocean survival, probably during residence in estuarial and inshore waters, has played a major role in determining the level of final ocean survival. Among pink and sockeye salmon that entered the sea in the same year there is some similarity in early ocean survival. The latter relationship, if confirmed, may become useful for predicting sockeye ocean survival one or two years before the adult fish return.

ISSN:0706-652X    

DOI:10.1139/f58-050

出版商:NRC Research Press    

年代:1958

数据来源: NRC