摘要:

By a modification of the DeLury method an estimate is made of the stock of lemon sole (Parophrys vetulus) on the fishing grounds in Hecate Strait, British Columbia. The method is based on (1) the trend in catch of tagged fish per unit of effort in relation to accumulated catch of tagged fish, and (2) the trend in catch of untagged fish per unit of effort in relation to accumulated catch of untagged fish. At the start of the experiment 4.72 million pounds are estimated to have been present, while during the experiment 3.74 million pounds entered the area of fishing, 3.26 million pounds emigrated from it, and 2.54 million pounds were caught.A Petersen-type estimate based on the ratio of tagged to untagged fish was 4.70 million pounds present at the start of the experiment—practically identical with the one derived from catch-effort information. Total population for the year (1950) is estimated as 9.8–12.2 million pounds, including catch and possible emigration prior to the experiment, the stock on the fishing grounds at the start of the experiment, and the immigration subsequently.The average annual survival rate of age VII – age IX lemon soles in Hecate Strait has decreased from 0.770 to 0.614 during the period of growth of the fishery, 1944–1951. From this difference the average rate of exploitation is estimated as 16 to 20 per cent and the average population as 8.9 to 11.5 million pounds. Since this range is nearly the same as the range described above, it is concluded that almost the whole of the Hecate Strait stock was accessible to fishing in 1950, which was a year of unusually high production.

ISSN:0706-652X    

DOI:10.1139/f53-027

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

THEmacroscopic bottom organisms of Great Slave Lake were sampled with more than 600 dredgings in the summers of 1944 to 1947. Additional ecological information was obtained from qualitative collections and from the examination of stomach contents of fish. The large area (10,500 sq. mi.) and extreme depth (2,000 ft.) of the lake necessitated special equipment and sampling procedures which are described.The bottom fauna of Great Slave Lake is typical oligotrophic, dominated by the amphipodPontoporeia affinisand including several species of sphaeriids (Pisidium), oligochaete worms and chironomid larvae (mostlySpaniotoma). In these respects the bottom population resembles those of Lakes Athabaska, Reindeer, Winnipeg and Michigan. In the extreme depths, 200–600 metres, of Great Slave Lake the bottom fauna is made up of single species of amphipod, ostracod, nematode, oligochaete, sphaeriid and chironomid. Attention is drawn to the contrast between this restricted fauna of a recent glacial lake and the great numbers of species found in ancient lakes such as Baikal and Tanganyika.The average bottom population for the whole lake is 1,603 organisms per square metre and 3.7 kg. dry weight per hectare. However, in Yellowknife Bay the population is double this general average, while in McLeod Bay, of the east arm, it drops to one-quarter. Edaphic, climatic and morphometric factors are discussed in explaining these differences between areas. The bottom population of the upper 50 metres is fairly heavy. It declines rather rapidly from 50 to 150 metres, but is relatively constant from 200 to 600 metres.The heavily silted area off the Slave River Delta has a bottom population heavier than that at similar depths elsewhere in the main lake. Oligochaetes and nematodes are more numerous in the silted area while molluscs and ostracods are much reduced. Bottom organisms provide about 40 per cent of the food of the main fish in the lake. Two species of whitefish and two species of suckers obtain more than 90 per cent of their food from bottom organisms.The average weight of bottom organisms in ten large lakes has been compared and found to show an inverse relation to mean depth. A formula has been derived and a curve drawn to describe this relationship. The implication is that productivity is dominated by morphometric conditions in these large, deep lakes.

ISSN:0706-652X    

DOI:10.1139/f53-028

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f53-029

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Chum and coho salmon fry respond positively to changes in water flow by swimming against the current. The magnitude of the response varies with the intensity of the current. Currents eliciting optimum response differ for the two species. Both species respond to the stronger of two parallel laminar currents but, after a time, coho fail to discriminate between small differences while the chums move continuously into the greater flow. No evidence of adaptation is apparent in a two-hour period with rapid complex turbulences. In turbulent water coho fry make a sharper initial response than chum fry but do not seem to maintain the peak response over as wide a range of turbulences.

ISSN:0706-652X    

DOI:10.1139/f53-030

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Infestation experiments carried out in 1947 and 1948 showed that the harbour seal (Phoca vitulina) was a definitive host of a larval nematode found in the flesh of the Atlantic cod (Gadus callarias), smelt (Osmerus mordax), Canadian plaice (Hippoglossoides platessoides) and eelpout (Macrozoarces americanus). Adult worms recovered from experimentally infested seals were identified asPorrocaecum decipiens. Some larvalPorrocaecumin the four species of fishes studied wereP.decipiens.The worms lost their larval characteristics by moulting between the third and sixth day following introduction into the seal. Sexual maturation proceeded rapidly after the eleventh day and some males and females matured before the twentieth day. Maturation was accompanied by a distinct increase in size.

ISSN:0706-652X    

DOI:10.1139/f53-031

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Experiments to deflect young spring salmon during their night-time migration by means of a beam of light and/or a "wall" of bubbles were conducted in a canal near Courtenay, B.C. By use of hoop nets it was discovered that under natural conditions no significant difference existed in the respective catches of the spring salmon underyearlings moving downstream on either side of the canal. A significant difference was obtained, however, when a narrow beam of light was directed into the water at a downstream angle in front of one net. A reduction to about one-third the expected catch resulted with either continuous or flashing light. The "wall" of bubbles, in a similar position, did not reduce the catch.Cut-throat trout fry and hatchery-reared Kamloops trout fingerlings were not deflected under these conditions.

ISSN:0706-652X    

DOI:10.1139/f53-032

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f53-033

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

The spectrum of the acid-soluble fraction of chitin is determined in dilute hydrochloric acid. It is found that the chitin forms a proton adduct whose equilibrium constant is approximately calculated from the spectral data.The constant for the proton adduct is carefully determined by a titration method, and its relation to some of the structural features of the molecule is indicated.

ISSN:0706-652X    

DOI:10.1139/f53-034

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

The proteolytic activity of an enzyme preparation from the pyloric caeca of redfish (Sebastes marinus) was studied and measured colorimetrically by the biuret reaction. The optimum temperature of this preparation was found to be 51–52 °C. A statistical study of the data showed the optimum pH to be 8.75, or slightly higher than the optimum pH of trypsin. A comparison of the actions of a commercial leather bate, hog intestinal mucosa, papain, pancreatin, trypsin and the caecal enzyme of redfish on casein led to the conclusion that the pyloric caeca of redfish would furnish a suitable material from which to prepare a leather bate.

ISSN:0706-652X    

DOI:10.1139/f53-035

出版商:NRC Research Press    

年代:1953

数据来源: NRC