摘要:

Identifications were made of ascarids collected from 1948 to 1956 from the stomachs of 318 harbour seals (Phoca vitulina), 812 harp seals (P.groenlandica), and 127 grey seals (Halichoerus grypus) killed in several localities along the Atlantic coast of Canada.Porrocaecumand 2 other genera of ascarids, tentatively identified asAnisakisandContracaecum, were present in each species of seal. All 112 malePorrocaecumthat were identified to species wereP.decipiens.Almost all stomachs of harbour and grey seals at all seasons and in all localities containedP.decipiens. Considering all localities, the overall average incidence was about 20 adultP.decipiensin harbour seals and about 100 in grey seals.P.decipienswas normally much rarer in the stomachs of harp seals than in the other seals. It appeared most frequently in harp seals taken around the Magdalen Islands in April and May. The incidence of adultP.decipienswas much lower during the breeding season of the seals and during their southward and northward migrations within the Gulf of St. Lawrence. The incidence ofP.decipiensin harp seals from the east coast of Newfoundland was very low.The relative importance of each species of seal as a vector ofP.decipiensis as follows. The harbour seal is the most important in the Bay of Fundy and along the southwestern coast of Nova Scotia. Elsewhere harbour and grey seals occur in approximately equal numbers. In such localities the grey seal is probably more important than the harbour seal. The harp seal is about 100 to 200 times as numerous, while in the southwestern Gulf of St. Lawrence, as the combined populations of harbour and grey seals there. Despite this great numerical superiority the harp seal does not appear to be more important than the other seals as a host ofP.decipiens.The relation between each species of seal and the incidence of larvalP.decipiensin Atlantic cod (Gadus callarias) is discussed.

ISSN:0706-652X    

DOI:10.1139/f58-023

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Late in 1953 when large haddock became scarce on the Newfoundland banks, fish plants, which previously had found haddock less than 45 cm. (18 in.) in length to be unacceptable for filleting, began to handle quantities of smaller haddock, 33 to 43 cm. (13 to 17 in.), and generally in an ungutted condition.Determination of the trimethylamine values of fillets from round and gutted haddock showed average values of 0.66 mg. per 100 g. of fillets for round and 0.73 for gutted fish from research vessel and 1.39 for round and 1.61 for gutted from commercial trawlers. These differences were not statistically significant. Using trimethylamine values as indicators of spoilage, round haddock were kept under ice up to 9 days under experimental conditions and produced unspoiled fillets.

ISSN:0706-652X    

DOI:10.1139/f58-024

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Individually marked Japanese oyster drills,Ocinebra japonica, were presented with a choice of four different food organisms: mussels (Mytilus edulis); clams (Venerupis japonica); and oysters (Crassostrea gigasandOstrea lurida). During the course of the 65-day experiment mussels constituted 42.6 per cent of the food organisms attacked by drills; clams, 36.5 per cent; and oysters, 20.9 per cent. The average time that anOcinebratook to drill though a shell and finish feeding on the body mass are: mussels, 4.98 days; clams, 6.31 days; Olympia oysters, 5.70 days; and Pacific oysters, 14.0 days (on the basis of one Pacific oyster). Experimental evidence suggests that a drill will continue to attack the same species of food organism that it had attacked previously, rather than moving to an easily accessible organism of a different species.

ISSN:0706-652X    

DOI:10.1139/f58-025

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The efficiency of candling cod fillets was studied using various values and colours of light transmitted through the cod flesh and various values of incident light. It was found that there was no advantage gained in using other than white light for transmission through the fillet. It was also found that a low level of incident light was desirable if the maximum number of parasites is to be detected.

ISSN:0706-652X    

DOI:10.1139/f58-026

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

In order to provide for ideal conditions of temperature and relative humidity in artificial dryers for salt fish a new method of control has been devised. A thermocouple, inserted in the flesh near the surface, regulates temperature of the air circulating in the dryer. Experiments with light and heavy salted fish confirmed theoretical considerations. The new method increases the drying rate, permits drying under unfavourable atmospheric conditions and avoids over-drying of the surface. Consequently, the difficulty of obtaining uniform batches of choice quality has been minimized. Light salted fish can be dried in three separate periods instead of four.

ISSN:0706-652X    

DOI:10.1139/f58-027

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The component fatty acids of the phospholipids of fresh and light salted cod flesh were determined. During the preparation of light salted "Gaspé cure" codfish 77% of the phospholipids fatty acids are set free. The fatty acids liberated are mainly the C20and C22highly unsaturated. The C92acids have a mean unsaturation of −11.5 H. The C16saturated and unsaturated acids are also preferentially liberated.

ISSN:0706-652X    

DOI:10.1139/f58-028

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f58-029

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Death occurs in fishes under certain circumstances following severe muscular activity. The precise cause of death is not yet known. However, it is possible that the severe disturbance to acid-base relationships following the large increase of lactic acid liberated from muscle glycogen may be the principal cause of death. Hyperactivity as a lethal factor in fishes is important in the study of biology of fishes and fisheries management.

ISSN:0706-652X    

DOI:10.1139/f58-030

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The cruising speeds of underyearling and yearling sockeye and coho salmon were determined in a rotating annular trough, for acclimation temperatures ranging from 1° to 24 °C. Variation in swimming speed characterized the first 40 to 50 minutes; subsequently a relatively steady state was obtained.Optimum cruising speeds occurred at 15 °C. for sockeye and 20 °C. for coho. Maximum sustained levels fell mainly between 1.0 and 1.5 ft. per second (30 and 45 cm. per sec.).Exercised young coho showed improved performance over those raised in standard hatchery troughs.The significance of the relative swimming capacities of the two species, and the effect of temperature, is discussed in relation to their ecology.

ISSN:0706-652X    

DOI:10.1139/f58-031

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Laboratory studies of preferred temperature with yellow perch (Perca flavescens) are compared with results from 21 other species. These show that temperature, if acting alone, can determine the distribution of fish in laboratory apparatus. Factors such as light, conditioned responses related to feeding routines, and social behaviour can interfere with the expression of the response to temperature. Subdued lighting conditions were necessary in the experiments withOncorhynchus,SalvelinusandCoregonus, whereas full daylight was required in experiments withPerca flavescens.The level of thermal acclimation influences the range of temperature preferred. In general the preferred temperature is considerably higher than the acclimation temperature at low thermal acclimations, but this difference decreases up to the final preferendum, where both coincide. The final preferendum and the relation between acclimation and preferred temperature is characteristic for the species. The shape of the resulting curve may have some value in interpreting observations of fish mortalities and distribution in nature. The final preferendum of the yellow perch from the present work was 24.2 °C., from other work using older fish it was 21.0 °C.Summer field observations of yellow perch in Lake Nipissing, Costello Lake and Opeongo Lake in Ontario, showed average thermal distribution of 19.7 °C., 21.0 °C. and 21.2 °C. respectively. This agrees well with 20.8 °C. observed for four Wisconsin lakes. Oxygen depletion reported for Tennessee Valley reservoirs, distribution of primary prey species of lake trout in New York waters, and other factors, have been shown to modify the thermal distribution in nature. Differential sex response to temperature may be important in the perch. Field observations of thermal distributions for other species are also presented.A comparison of the laboratory and field data shows good agreement with fish having colder final preferenda:Salvelinus fontinalis,Salvelinus namaycush,Salvelinushybrid andCoregonus clupeaformis. Fish with warmer final preferenda, such asMicropterus salmoides,Micropterus dolomieuandLota lota lacustris, showed higher temperatures in the laboratory than was shown by field observations. YoungPerca flavescensshowed similar results, but experiments with older perch showed excellent agreement between laboratory results and held observations. The lack of agreement between laboratory results and field observations is attributed to age differences; laboratory experiments being performed with young fish and held observations being made on older fish.

ISSN:0706-652X    

DOI:10.1139/f58-032

出版商:NRC Research Press    

年代:1958

数据来源: NRC