摘要:

The reproductive rate of brook trout populations from infertile Pennsylvania streams was determined. The standing crops for eight streams varied between 14 and 41 lb/acre. Trout in age-groups 0 through III were found to grow slowly with very few individuals reaching a total length of 6 inches.The seasonal development of ova was determined by measuring all ova larger than 0.2 mm from selected females. The maturing ova of most females of age-groups II and III increased in diameter from 0.9 mm in February to 1.0 mm in June, 1.75 mm in July, 2.5 mm in August, 3.0 mm in September, and 4.0 mm in October. Maturing females could be distinguished from immature females by late August or early September on the basis of ova diameters. The mean diameter of ripe ova from 67 females was 4.05 mm with a range between 3.37 and 5.01 mm for individual trout ranging from 4.6 to 8.6 inches total length.The relationship between the number of mature ova and the total length of the female for one population was described by a curvilinear regression (log Y = −0.5361 + 3.23 log X, where Y = number of eggs, and X = the total length of the fish) for brook trout between 3.6 inches (18 eggs) and 7.7 inches (213 eggs). Variation in this relationship existed among streams.Ova production was estimated as 9050 ova per acre for one population and 13,620 ova per acre for another. Age-group-I females contributed approximately 9% of this production; age-group-II females, 54%; and age-group-III females, 37%. An ecological life table was constructed for two populations comparing rates of survival, age-specific fecundity rates, and reproductive rates.

ISSN:0706-652X    

DOI:10.1139/f66-055

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The peak spawning period of American plaice was the first part of April for Flemish Cap and ranged from the end of April for the Grand Bank and surrounding areas to the first part of June for Labrador–Northeast Newfoundland Shelf. Average bottom temperatures during spawning ranged from about 3.5 C for Flemish Cap and the deep spawning areas to the north, to about −1.3 C for St. Mary's Bay and the northern half of the Grand Bank. For the Southeast Grand Bank, Southwest Grand Bank, and St. Pierre Bank average spawning temperatures were 1.1, 2.8, and 2.7 C, respectively.There was evidence that some older, larger fish spawned first and also that plaice in deep water spawned later than those from shallower depths. At the latter depths light was a possible factor.According to samples from St. Mary's Bay the development of the sex products for spring spawning was apparently controlled by water temperatures during the previous fall and late summer.Fifty per cent of the females from Flemish Cap were mature at 7.8 years, the bottom temperature being almost constant at 3.5 C. For other areas the number of years ranged from 12.2 for the Southwest Grand Bank, with prevalent temperatures 0–3, to 15.2 C for St. Mary's Bay where temperatures were −1 to 1.0 C. For males the range was from 5.3 years for the Southeast Grand Bank to 7.5 years for St. Pierre Bank, no data being available for Flemish Cap.

ISSN:0706-652X    

DOI:10.1139/f66-056

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The relation between free drip, fleshpH, and chalkiness in halibut was investigated. Free drip was found to increase continuously with decreasingpH in the rangepH 6.8–5.7. FleshpH varied somewhat with location in the body, tending to be higher nearer the head. The minimum fleshpH was reached within 24–43 hr of death and increased very slowly thereafter.All fish with a fleshpH below 6.0 were chalky, those with apH above 6.2 nonchalky, while in thepH range between 6.0 and 6.2 intermingling of chalky, borderline chalky, and nonchalky fish occurred. The use of fleshpH measurement as a means of classifying fish with respect to chalkiness appears to be worth consideration.

ISSN:0706-652X    

DOI:10.1139/f66-057

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

A pilot-plant procedure is described whereby marine oils with low to medium iodine values can be converted into fractions of methyl esters of denned fatty acid composition. Three major fractions were obtained having 61% saturated, 73% monounsaturated, and 72% polyunsaturated esters, respectively.Methyl esters were produced continuously and glycerol separated by centrifuge, the shorter chain-length esters distilled under vacuum and the remainder countercurrently fractionated with nitromethane. By cooling the nitromethane-rich raffinate, a highly unsaturated ester concentrate was obtained. Gas–liquid chromatography was used to follow the efficiency of the various steps.

ISSN:0706-652X    

DOI:10.1139/f66-058

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

In a recent paper by Larkin et al. (1964) reproduction curves are considered for life history stanzas, and a depensatory process related in form to the compensatory process of Ricker (1954) is presented. In the following development the necessity of defining such functions as two parameter systems is presented. A theoretical production curve based on the concept of hunger is derived. It is also shown that under conditions of extreme predation this curve approximates Larkin's depensatory production curve. The curve is applied to data for Adams River sockeye salmon.

ISSN:0706-652X    

DOI:10.1139/f66-059

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

An exploratory investigation has been made of the possibility of utilizing partial freezing as a means of preserving several species of groundfish. From the point of view of suppression of development of spoilage odours and belly burn, the procedure used was found to be superior to storage in either ice or refrigerated sea water (RSW), and the cooked texture of partially frozen fish, at least after reasonable periods of storage, was equal to that of fish stored by the other procedures. However, free drip was greater from the partially frozen fish, and fillets from such fish were softer and more fragile than those from RSW- or ice-stored fish.

ISSN:0706-652X    

DOI:10.1139/f66-060

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

A specimen ofBathypterois dubiusVaillant, 204 mm standard length, trawled by theA.T.Cameronat a depth of 750–805 m on the southwestern slope of the Grand Bank on May 2, 1959, is apparently the first record for the western North Atlantic. The specimen is illustrated and its characteristics described and compared with those of otherB.dubiusfrom the eastern Atlantic and the Mediterranean.

ISSN:0706-652X    

DOI:10.1139/f66-061

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

A method based on static bioassays was developed to measure the concentration of toxaphene before restocking of lakes treated with this toxicant. A double distillation technique was used to extract the toxaphene and concentrate it in a small volume of distillate. Bioassays were then carried out in 200-ml samples of distillate reconstituted with electrolytes to match a standard water. Guppies,Lebistes reticulatus(Peters), less than 7 days old were used as test organisms.The method developed was used to follow the detoxification of Midway Lake which was rehabilitated with toxaphene. Data on the rate of detoxification are presented.

ISSN:0706-652X    

DOI:10.1139/f66-062

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Intensive exploitation of commercial king crab populations at the south end of Kodiak Island has caused a reduction of individual crab size and, as the resource continues to be utilized at a high level, the recruits may eventually constitute the bulk of the harvest.Carapace length distributions of 3359 males obtained on August 10–11, 1963, from three fishing areas with different rates of utilization indicated that the size-class structure for the Sitkinak Island and Wide Bay areas were similar, but different from that of the Alitak Bay area.Comparison of length–frequency data collected from Alitak Bay in 1954 and 1963–64 indicated that larger size-classes have been cropped and are no longer abundant.

ISSN:0706-652X    

DOI:10.1139/f66-063

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The distillation method for determining the thiobarbituric acid value gave spurious results when applied to cod muscle containing trace amounts of Fe+++or Fe++. This was the result of metal-catalyzed oxidation that took place in the acidified tissue during distillation. It was prevented by replacing the oxygen in the distillation flask with nitrogen or by immobilizing the iron catalyst by addition of the disodium salt of ethylenediaminetetraacetic acid or propyl gallate.Complex organic iron compounds, copper salts, cysteine, or sodium chloride did not interfere with the TBA test.

ISSN:0706-652X    

DOI:10.1139/f66-064

出版商:NRC Research Press    

年代:1966

数据来源: NRC