摘要:

Parr–smolt metamorphosis in yearling Atlantic salmon was accompanied by variations in plasma and tissue electrolyte levels, and in tissue water distribution. Plasma chloride declined sharply with the onset of smoltification, but recovered to values somewhat higher than those seen in parr with the attainment of the silvery parr stage. Some decrease, with no evidence of a secondary increase, was observed in tissue chloride concentrations. Changes in chloride space values suggested that parr–smolt metamorphosis is also characterized by a shift of tissue fluids from the extracellular to the cellular phase. These variations in water–electrolyte balance are thought to reflect a premigratory activation and secondary suppression of the extrarenal salt excretion systems employed for osmotic and ionic regulation in sea water. Their occurrence in fish estimated upon the basis of morphological characters to be large parr suggests that the metamorphic process may occur earlier in the life cycle of this species than is generally recognized.

ISSN:0706-652X    

DOI:10.1139/f63-093

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

If it is assumed that rates of exploitation, regardless of where fishing takes place, can be adjusted to the needs for reproduction, maximum yield from stocks of north Pacific sockeye salmon (Oncorhynchus nerka) will then be a function of growth and natural mortality rates. Events during the last decade have demonstrated the vulnerability of this species to pelagic fishing during the penultimate and ultimate years of life. The instantaneous growth rate on a per-month basis (g) is estimated from diverse data by back calculation, tag and recapture, and size-at-time methods. A general consistency of results is apparent regardless of the method utilized. For 2-ocean annuli life history types, penultimate, ultimate. For 3-ocean annuli types, penultimateg = 0.059, ultimate. Ocean mortality models and rates derived by several researchers are reviewed and discussed. Using those proposed by the author, it is shown that the stock mass, hence the allowable yield, increases throughout the penultimate and ultimate years in the sea and reaches a maximum when the stocks approach the coast on the spawning migration. A conservative estimate of the potential increment, based on the 1957–1959 pelagic catches, is 14.2%. It is concluded that the yield of these stocks is seriously depressed by pelagic fishing.

ISSN:0706-652X    

DOI:10.1139/f63-094

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The field study of the bigmouth buffalo (Ictiobus cyprinellus(Valenciennes)), conducted mainly in 1955 and 1956, was concentrated on two small eutrophic lakes in the Qu'Appelle River drainage of Saskatchewan. The bigmouth buffalo reaches its northern limit of range in the Qu'Appelle drainage. Migration into Saskatchewan was probably through postglacial connections at the headwaters of the Mississippi and Red River systems. In the lakes studied, the species prefers water shallower than 5 m.The relation of standard length to fork length and of fork length to weight is presented graphically, and the latter described by the equation: weight in pounds = (0.00097 fork length in inches)2.91. Length–frequency distributions and age determinations from scale reading show that the population studied was largely the very successful 1948 year-class, produced in a year of extensive flooding. Annulus formation occurred during the second or third week in June. Growth of the 1948 year-class in Pasqua Lake was extremely slow, probably influenced by the cool climate and population density here.Food of young buffaloes was mainly Cladocera and Copepoda. Larger buffaloes ate about 75% Entomostraca and 15% chironomids, the latter more important as the size of fish increased. Analysis of the living habits of the food eaten, and the feeding mechanism of the buffalo, shows that they occupy a food niche overlapping both bottom feeders and limnetic plankton feeders.Sexual maturation, especially of females, was extremely slow both in age and size as compared with southern populations. Examination of gonads suggests spawning occurs about May 18–25. Egg measurements indicate that females do not all spawn each year. The contention by other investigators that spawning is "triggered" by addition of fresh water analogous to normal spring floods of the Mississippi River is supported by the present study.The population in the Qu'Appelle drainage is probably dependent on the very sporadic production of strong year-classes. A more stable population would require association with regular spring floods of a nearby river or marsh. Commercial removal from the viewpoint of greatest productivity is most economical at the smallest marketable size, as yearly weight gains are probably more than offset by natural mortality.

ISSN:0706-652X    

DOI:10.1139/f63-095

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Transparent colourless and opaque yellow tags of several types were applied to small perch, less than 15 cm in length, and larger suckers, 17 cm and greater, in Heming Lake, Manitoba, Canada. The return of opaque yellow tags was significantly smaller than that of clear transparent tags (less than one-half) for the small fish only. Tag type was relatively unimportant. This is interpreted as a higher predation rate, by pike, on small fish with opaque yellow tags.

ISSN:0706-652X    

DOI:10.1139/f63-096

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The dose–response relationship of 2-phenoxyethanol, as a general anaesthetic, in adult sockeye salmon (Oncorhynchus nerka) has been investigated. At 11 °C the effective dose (ED50) and lethal dose (LD50) were approximately 43 and 130 ml/100 Imperial gal, respectively. The therapeutic ratiowas more than 3, indicating a good margin of safety. At a lowered aquarium temperature of 4 °C the anaesthetic effects of 2-phenoxyethanol were potentiated. ED50and LD50at this temperature were approximately 25 and 130 ml/100 gal of water, respectively. The therapeutic ratio was more than 5, indicating that the margin of safety was increased by the decrease in temperature.

ISSN:0706-652X    

DOI:10.1139/f63-097

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Sockeye smolts, pink and chum fry, and pink and chum fingerlings (Oncorhynchus) were sequentially weighed and measured when alive and after death in water and after killing and storage in formalin up to 225 days. The fish shrank within 12 hours to 97% and by 30–40 days to 96% of live length. Further changes in length were not significant. These same relative changes were observed from fish of different sizes, and the values were not significantly different among groups preserved in formaldehyde solutions of fresh or sea water. In fresh water, fish gained weight while yet alive but under anaesthesia. In freshwater formalin, fish gained weight rapidly for 1 or 2 days, then lost weight at a decelerating rate to the time of last measurement. Fish killed and stored in salt water formalin lost weight for the first few days, then gained weight at a decelerating rate. Relative magnitudes and rates of change were inversely related to size of specimens contained in the sample. These changes had pronounced effects on relative condition factors which varied from 97 to 135% of live values depending upon size of fish, type of formalin and time in preservative.

ISSN:0706-652X    

DOI:10.1139/f63-098

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Adult sockeye salmon (Oncorhynchus nerka) captured during their spawning migration to Great Central Lake, British Columbia, show a consistent response in the laboratory to water taken from the outlet of the lake. The specificity of this response has been confirmed and the responses to water from streams feeding Great Central Lake have been determined. A portion at least of the stimulatory material is volatile and can be retained in a cold trap. Concentration of the active factor has been achieved by a freezing-out technique.

ISSN:0706-652X    

DOI:10.1139/f63-099

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The fecundity of Grand Bank haddock was investigated from 229 specimens collected during the early springs of 1957–61. It was found that fecundity increased at a rate proportional to about the fifth power of the body length and to the square of the age, the correlations between fecundity and length and between fecundity and weight being better than that between fecundity and age. Within any age-group fecundity was found to increase with length. Since the larger fish of an age-group are the first to mature, it is suggested that fecundity of individual fish may be more directly related to the number of times that the fish has spawned than to such parameters as length, weight or age. Certain differences in fecundity, found between the samples of the individual years, are discussed in relation to such environmental conditions as temperature in so far as it determines the degree of haddock concentration (thus affecting the food supply) at certain times which are probably critical during the early development and maturation of the ova.

ISSN:0706-652X    

DOI:10.1139/f63-100

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Minke whalesBalaenoptera acutorostratasupport a shore-based fishery in eastern Newfoundland. The appearance of minke whales here parallels the spawning concentration of capelin (Mallotus villosus) and lasts from late May to late July, the whales eating chiefly capelin with some cod and herring and other organisms. Summer distribution extends north to Ungava Bay. A return migration is not noted in Trinity Bay before catching ends in late October but reports from the Labrador coast indicate that many whales pass through just before freeze-up in November or December. The catch in Newfoundland consists mainly of large mature animals, and there is some evidence that many calves may remain in summer in more southerly waters. Body form, colouration and life cycle show no differences from minke whales of European seas. Ear plugs were rarely found to show readable growth layers in minke whales.

ISSN:0706-652X    

DOI:10.1139/f63-101

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Nine specimens ofArtedius meanyi(=Ruscarius meanyi), previously known only from the types, have been taken in Howe Sound and the Strait of Juan de Fuca. The genusRuscarius, of whichmeanyiis the type, though retained as a subgenus, is placed in the synonymy ofArtedius. The subgenusRuscariopsHubbs is considered a junior subjective synonym of the subgenusRuscariusJordan and Starks.A.meanyiis redescribed and compared with the other members of the genus.

ISSN:0706-652X    

DOI:10.1139/f63-102

出版商:NRC Research Press    

年代:1963

数据来源: NRC