摘要:

Lake trout (491 in all),Salvelinus namaycush, planted as yearlings in Lake Manitou in 1952 were tagged at age VII when taken in trap nets during spawntaking operations. At the same time 259 native adult trout of unknown age were also tagged. In spawntaking operations in subsequent years tag numbers were noted for tagged fish recaptured and the fish returned to the lake after normal spawntaking. Both groups were estimated to have suffered a decrement of 25% per year. The lake trout planted were given a distinctive fin clip on planting so that comparisons of recaptures of tagged and untagged planted fish permitted estimates of the survival of the total plant. The mean annual mortality rate from the time of planting was also estimated at 25%. Trout planted later appeared to have suffered a similar mortality rate. Observations on planted lake trout of known age indicated that the peak age for first spawning in females was age VI. There is no predation by sea lamprey in Lake Manitou.

ISSN:0706-652X    

DOI:10.1139/f68-201

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Ninety-three species of Bryozoa are reported here from the area of arctic Canada extending from Belle Isle Strait westward to Herschel Island. Bathymetric and distributional data, both local and regional, are given for all species. Photomicrographs are provided for 47 species. One species,Stomachetosella hincksi, is described as new.Electra crustulenta(Pallas) var.arcticaBorg is accorded specific rank.Callopora smittiKluge is referred to the genusCopidozoumandHippodiplosia obesa(Waters) is transferred to the genusSchizoporella. A new family, Hincksiporidae, monotypical forH.spinulifera(Hincks), is attributed to the Ascophora Imperfecta.Porella princeps(Norman, 1903b) is considered to be a synonym ofPachyegis producta(Packard, 1863), andCodonellina operculataMawatari (1956) a synonym ofSchizomavella porifera(Smitt, 1867). The following eight species are new for arctic Canada:Terminoflustra barleei,Scrupocellaria arctica,Reginella spitzbergensis,Hippoporina cancellata,Schismopora nodulosa,Escharella thompsoni,Smittina mucronata,Pseudoflustra sinuosa. Except forR.spitzbergensisandH.cancellata, these are also new for arctic North America.The zoogeographical relationships of the fauna are discussed, three main types of distribution being recognised, viz., panarctic, boreal-panarctic, and Atlantic–arctic. No relationship between faunal distribution and the surface waters of the arctic and subarctic zones is apparent, the majority of species transgressing both. Compared with the bryozoan fauna of the antarctic region, the arctic group is impoverished in indigenous taxa.

ISSN:0706-652X    

DOI:10.1139/f68-202

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

As indicated by thin-layer chromatography, hatchery-reared Atlantic salmon parr degraded DDT, absorbed from aqueous suspensions, to DDE and TDE within 9 hr. DDT adsorbed on external surfaces of the salmon was not degraded.

ISSN:0706-652X    

DOI:10.1139/f68-203

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

In glacial marine sediments from the St. Lawrence estuary, iron varies between 1.32 and 5.42%, manganese between 0.043 and 0.28%, and titanium between 0.31 and 0.64%. The regional distributions of these elements are related to sediment texture. Analyses of individual sediment size-fractions show that Fe, Mn, and Ti concentrations generally increase with decreasing grain size. Variations in elemental ratios between the different grades suggests that not all of the Fe and Mn is located in detrital silicate minerals. Dithionite extraction of selected sediments resulted in preferential dissolution of 3–16% of the total iron, presumably that derived from amorphous and crystalline iron oxides and from sorbed material.Hydroxylamine–hydrochloride removed 5–60% of the total manganese, presumably that derived from exchangeable Mn, easily reducible Mn oxides, and sorbed Mn material. The soluble fraction is highest in freshly deposited pelites from the center of the estuary. Soluble Fe and Mn occur as oxide films on the particles deposited from suspension, and the amount held depends on rate of deposition and on the physicochemical conditions in the waters and in the sediments. In contrast, Ti occurs in detrital minerals and accumulates at the same rate as detrital sedimentary material. It is unaffected by environmental changes. This investigation shows that, despite the derivation of the sedimentary material from the Canadian Shield predominantly by nonchemical erosional processes, small but significant chemical modification of iron- and manganese-bearing material is taking place in response to present physicochemical conditions.

ISSN:0706-652X    

DOI:10.1139/f68-204

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A method is described of estimating fish stocks by length-groups acoustically. Hake off southern Africa were recorded as individuals on the paper record of a Kelvin Hughes "Humber" echo sounder down to 350 fath. Signal strengths of single fishes were observed on the cathode ray tube and the target strengths of fishes are known; estimates of fish sizes were made. The signals were considered as being received from a mean angle (to the axis of transmission) in the volume insonified. Hence, average target strengths, average numbers/unit volume, and average heights above the sea bed were calculated.The echo survey made between Cape Town and Walvis Bay was expressed as numbers of fish/unit volume in a range gate of 1 or 4 fath above the sea bed. A length distribution of the hake stock was derived.

ISSN:0706-652X    

DOI:10.1139/f68-205

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Two new species ofGyrocotylehave been found in the intestine of the deepwater chimaeraHydrolagus affinisof the northwest Atlantic.Gyrocotylehad not previously been recorded from this host species.Descriptions are provided for ♂-mature and ♀-mature specimens ofGyrocotyle majorn.sp. and ♂-mature specimens ofGyrocotyle abyssicolan.sp. The systematic status, distribution, and some host relationships of these species are discussed. Within the subgenusAmphiptyches, two groups of species are recognized: theurna-group, includingG.major, and theconfusa-group includingG.abyssicola. Geographical variation is shown byG.major. Allometric growth of different parts of the body inG.majoris described. TheseGyrocotylespecimens are the largest yet recorded,G.majorattaining a maximum length in our collection of 200 mm andG.abyssicolaof 138 mm. The size ofG.majorincreases with size of

ISSN:0706-652X    

DOI:10.1139/f68-206

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Aggressive behaviour of Atlantic salmon (Salmo salar) parr, tested in groups of eight, was greater during 3 days of deprivation of food than during 3 days of feeding. Frontal and lateral displaying appeared to increase more than charging and nipping. Increased agression was only partly a result of increased locomotion, and therefore was partly a direct effect of hunger.Strong social hierarchies developed, larger fish nipping smaller ones more than the reverse. The correlation between size and hierarchical status was usually sufficient to account for the strength of hierarchy observed.Upon deprivation of food the dominant of any pair of socially unequal fish on the average increased its nipping of the subordinate. The nipping rate of dominants by subordinates did not change consistently; many low ranking fish decreased their nipping rate upon deprivation. These results would strengthen hierarchies during deprivation. Initiation of attacks by small fish, as opposed to nipping, increased consistently during deprivation.Nipping was more frequent between fish of equal status and size than between fish of unequal status or size. This could have accounted for the strength of hierarchies in groups in which the correlation between size and position was insufficient to do so.The increase in aggression upon food deprivation could function to increase the size of feeding territories when food is scarce. This and the strengthening of hierarchies would cause emigration of some fish from the area. Concentration of aggression between fish of equal size and status could permit parr of different ages to coexist.

ISSN:0706-652X    

DOI:10.1139/f68-207

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Growth rates and changes in some chemical constituents were investigated in laboratory-reared and wild coho salmon in the pre-smolt, smolting, and early post-smolt stages of their life cycles.Laboratory-reared pre-smolts of coho salmon continued to grow during fall and early winter but at an ever diminishing rate. During late winter, spring, and early summer, growth in both length and weight of these fish was exponential with time. In wild coho pre-smolts there was no apparent winter growth but, with the onset of warmer waters and longer day lengths in the spring, growth in both length and weight became exponential with time. Exponential growth continued in wild post-smolts held in seawater pens but at a slower rate than during smolting.It is postulated that the powerbin the weight–length formula W = aLbis approximately 3.2 and that during smolting, when the fish are becoming more streamlined, the parameteradecreases from approximately 7.5 to about 6.2.Guanine levels in belly skin, which appeared to be related to lighting conditions and physiological state of the fish rather than to length or weight, increased during smolting to about 6 μg/mm2skin and remained at these levels.In pre-smolt laboratory-reared fish total lipid increased with increasing growth. With further weight increases during exponential growth, the weight of lipid remained relatively constant and the amount of lipid per unit weight decreased. A decrease in percent lipid did not occur in wild fish.Total moisture, dry material, and nitrogen were linearly related to weight in the size-range investigated, but a sharp inflection in each least-square fit line occurred for moisture and dry material at a fish weight of 15 g and for total nitrogen at 7.5 g. These shifts in composition were related to fish size rather than to age, environment, or physiological state. During exponential growth, moisture, dry material, and nitrogen increased with increasing weight but whereas moisture increased at a slower rate than weight, solids and nitrogen increased more rapidly.

ISSN:0706-652X    

DOI:10.1139/f68-208

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The fatty acid compositions of six samples of depot fat taken from harp seals (Pagophilus groenlandica), ranging in age from 1 to 2 days to adult, and a sample of milk lipids, were determined by gas–liquid chromatography (GLC). Three depot fat samples taken from hooded seals (Cystophora cristata), a sample of milk lipids from this species, and commercial seal oils from 4 years' production were similarly analyzed.No significant differences could be found between the composition of the milk lipids and the depot fat of the harp seals at the different ages, other than slightly lower iodine values in the younger animals (avg 140.6 vs. 148.9). The lipid samples from hooded seals had low iodine values (107–127) and correspondingly lower concentration of highly unsaturated fatty acids. The ratio of the fatty acids 22:5ω3/22:6ω3 could be used to differentiate between depot fat from harp seals (ratio 0.51–0.74) and that from hooded seals (ratio 0.25–0.42) in the samples analyzed.Commercial oils, which consist essentially of oil from harp seals, were similar in composition to oil prepared from this species alone.No difference could be found in the iodine values or fatty acid compositions of samples taken from various parts of the animal or from samples representing a cross section of blubber.

ISSN:0706-652X    

DOI:10.1139/f68-209

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A comparison was made of 1955–60 and 1961–66 monthly mean 200-m temperatures in eight 1-degree quadrangle areas in the Gulf of Maine and along the Continental Slope between Nova Scotia and Long Island. Temperatures were appreciably lower in all areas during the latter period. The subsurface temperature trends paralleled trends in surface temperatures previously documented. The distribution of temperature at 200 m along the edge of the Continental Shelf during March, May–June, and September 1965 and 1966 and the distribution of temperature, salinity, and dissolved oxygen on sections made across the Continental Shelf in September 1954, 1965, and 1966 showed that the cooling and warming trends are accompanied by changes in the composition of the subsurface water. Cold years occur when Slope Water is displaced or modified by Coastal Water of Labrador origin. Warm years occur when Slope Water borders upon the 200-m isobath and the ratio of Coastal to Central Atlantic Water is low.

ISSN:0706-652X    

DOI:10.1139/f68-210

出版商:NRC Research Press    

年代:1968

数据来源: NRC