摘要:

Primary productivity and zooplankton data from Ocean Station P are used to compare estimates of phytoplankton and herbivore production calculated on the assumption of continuous grazing by the animals with estimates obtained on the assumption of three different types of nocturnal grazing. Effective plant production, that corrected for the effects of grazing on the size of the phytoplankton stock and hence on the magnitude of the plant respiratory loss, was less than the measured production and was least under the assumption of continuous grazing. The small differences in effective production resulting from the choice of different grazing schemes resulted in large differences in estimates of secondary production. The relative effect of assuming different grazing schemes on the estimate of secondary production varied markedly with zooplankton respiration and with the phytoplankton growth rate.

ISSN:0706-652X    

DOI:10.1139/f69-025

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Dugesia lugubris(Schmidt), a Palaearctic freshwater triclad, is described from North America. A morphological and taxonomic evaluation is presented and comparisons with European material and data are made, confirming the initial diagnosis. The known distribution of the species in North America is discussed in relation to what is known of its distribution and ecology in Europe, and it is concluded that the introduction is probably unique and of recent occurrence. It represents the second authenticated case of passive dispersal by man in the freshwater Tricladida, and is almost certainly a result of the shipping plying between the St. Lawrence River and various European ports. The present findings in no way conflict with the opinions of modern American taxonomists that early records ofD.lugubrisin North America are the results of mis-identification ofCura foremanii(Girard). A key for the separation of these two superficially similar species is provided.

ISSN:0706-652X    

DOI:10.1139/f69-026

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

A comparative study was made at Babine Lake, British Columbia, of the distribution, growth, and survival of sockeye salmon fry resulting from the same parental stock but reared in natural and artificial streams. Fry produced from natural spawning in the Fulton River and from eyed eggs planted in an adjacent artificial spawning channel were marked distinctively, released, and later recovered in the lake nursery area and at the lake outlet at time of seaward migration. Both groups dispersed rapidly and widely into the main lake basin and apparently mixed extensively with sockeye produced from other main lake tributaries. Lake distribution of marked fish, and the underyearling population as a whole, was not uniform nor static and the fish were concentrated in different lake areas at different times of their first growing season. River and channel fry were comparable in mean length at time of release but subsequently channel fish were smaller. Their smaller size appeared to result from late lake entry and a slower rate of growth for a short period thereafter. Over most of the growing period (June 25–October 25) rates of growth in length were similar (instantaneous daily rates of 0.00687 and 0.00737). No significant difference in survival rates of the two groups could be detected for the first 5 months of lake residence. Production of age I seaward migrants was less for river fish than for channel fish but no significance was attached to the small difference observed. These findings are discussed with respect to a fish-cultural scheme which is aimed at increasing adult production by making fuller use of the lake's capacity to rear young sockeye.

ISSN:0706-652X    

DOI:10.1139/f69-027

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Tagging studies with naturally produced smolts from the Northwest Miramichi River showed that adult salmon from this river make substantial contributions to commercial fisheries in the Miramichi area (trapnet fisheries in the Miramichi estuary and the adjoining drift-net fishery), around insular Newfoundland, and along the west coast of Greenland. Minor contributions are made to other commercial fisheries throughout the Canadian Maritime Provinces. Tagged Northwest Miramichi salmon were taken by angling in the Miramichi system only, principally the Northwest Miramichi. Commercial fisheries accounted for 32 and 87% of known recaptures of tagged grilse and larger salmon respectively; anglers, 24 and 10%; fish available for spawning, as measured by a counting fence, were 44 and 3%. The ratio of grilse to larger salmon among total recaptures was about 2:1; in fish available for spawning, about 28:1.

ISSN:0706-652X    

DOI:10.1139/f69-028

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Investigation of the benthic fauna of the Speed River, Ontario, was carried out from June 1966 to September 1967. Upstream movement of substantial numbers of invertebrates was detected using solid-walled traps with induced current, and Terylene net traps. The mechanism for this was largely positive rheotaxis, but positive skototaxis and the release of phototactic control probably governed the distance covered. During the winter, statistically greater movement occurred in areas adjacent to the banks than in midstream, but in summer the midstream areas contributed most of the migrants. Artificially darkening the traps increased the biomass moving into them. Movements upstream counteracted 6.5% of downstream drift by numbers and 4% by weight, but no comparison of relative distance travelled was made. The upstream movement was of sufficient quantity and species diversity to account for recolonization of dried-out or erosion-denuded areas.

ISSN:0706-652X    

DOI:10.1139/f69-029

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Bacteriovorous Protozoa and heterotrophic bacteria quantitatively cultured from 31 samples collected at eight stations in Puget Sound and three in the adjacent Pacific Ocean (one station being 1520 m deep) ranges from undetectable to approximately 1000 Protozoa per ml and 5–80,000 bacteria/ml. Flagellates in the generaBodo,Oikomonas,Monas,Rynchomonas, andActinomonaswere the most prevalent forms cultured. One ciliate and several sarcodinoids were also grown. The regression of predatory Protozoa on prey bacteria in sediment samples was calculated to be 580 bacteria for every bacteriovorous protozoan. Population densities of both bacteriovorous Protozoa and heterotrophic bacteria in the samples decreased from sediment to the water column, and from shore seaward. The ecological role of bacteriovorous Protozoa in the shallow and deep sea is discussed.

ISSN:0706-652X    

DOI:10.1139/f69-030

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Zooplankton standing crop was estimated in the Arctic Basin north of Greenland and in the East Greenland Current from tows made from drifting ice island Arlis II. Number 20 mesh closing net hauls indicated that most of the zooplankton biomass was concentrated in the top 500 m in both winter and summer. The bulk of the zooplankton standing crop was copepods which contributed 86 and 77% of the biomass in the Arlis II samples from the Arctic Basin and East Greenland Current, respectively.Calanuswas the most important genus, making up one-half the weight of the zooplankton. Zooplankton biomass under a square meter of sea in the top 500 m averaged 0.29 g dry weight in the Arctic Basin north of Greenland and increased to 4.52 g in the upper 500 m of the East Greenland Current. It is postulated that Arlis II was carried south near the eastern edge of the East Greenland Current and that most of the plankton occurring in the rich samples from the East Greenland current was contributed by the Greenland Sea through vigorous mixing.

ISSN:0706-652X    

DOI:10.1139/f69-031

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Four species of copepods belonging to the family Lernaeopodidae are described. One of them (Lernaeopodina longibrachia) is new to Canada. Two (Clavella pinguisandClavellodes rugosus) have been previously reported from Canadian waters, thoughC.pinguisis very poorly known. The fourth species (Clavellomimus macruri) is placed in a newly established genus. It is concluded that the species hitherto placed inClavellodesshould be divided into three groups: one containing onlyC.rugosus, the second containing all species distinguished by the presence of aliform expansions at the base of the second maxillae, and the third accommodating those without such expansions. All three groups have almost identical males.

ISSN:0706-652X    

DOI:10.1139/f69-032

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Detailed distributions are given for 35 species of fish collected in southern Alberta. These include the first record ofMoxostoma anisurumin Alberta, new records in the South Saskatchewan River drainage, and extensions of the known ranges of a number of species within the province. Records reported by earlier investigators are included with the aim of providing a complete account of the distributions of fishes in this region.

ISSN:0706-652X    

DOI:10.1139/f69-033

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

This is a study of the robustness, in estimating population size, of the usual DeLury Estimator and three modifications of it derived from the generalized exact deterministic catch equation of Beverton and Holt (1956, 1957). These estimators are called the Generalized DeLury Estimator, the Weighted Generalized DeLury Estimator, and the Effort-corrected DeLury Estimator.A computer was used to simulate varying environmental conditions, which included combinations of several vectors of catchability and effort and several types of random error. The results indicate that the generalized estimator is overall the best, at least for these simulated data. The effort-corrected estimator is just as effective, but requires effort correction. The usual DeLury estimator underestimates on the average. The weighted estimator has high variance.Catchability behavior has a marked effect on accuracy of any of these estimators. An increase in catchability from a previously constant level results in a subsequent increase in the estimate of population size. A decrease in catchability results in a decrease in the estimate. If catchability cycles, the estimate cycles with the same crest and period.Effort has little effect, at least for the vectors studied in this model.

ISSN:0706-652X    

DOI:10.1139/f69-034

出版商:NRC Research Press    

年代:1969

数据来源: NRC