摘要:

The discovery, in Canadian Atlantic waters, ofTanypleurus alcicornisSteenstrup and Lütken, 1861, is reported. This is the first find of the species since its description. Its morphology, including the structure of appendages, is examined. A new family Tanypleuridae is proposed.

ISSN:0706-652X    

DOI:10.1139/f69-131

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The community concept has had a long, complex history in plant and animal ecology. Divergent views about the nature of communities have been most marked in plant ecology: the Zurich–Montpellier school regarded plant communities as largely abstract, based on a mosaic of vegetation, whereas the Uppsala school and other northern plant ecologists regarded communities as concrete, quantifiable units. The analogy between communities and organisms has been used often, particularly in American dynamic ecology, although the analogy can only be a loose one. Communities have also been regarded as abstractions from independent continuous distributions of the individual species. This idea has been used in recent gradient analysis of plant communities.Similar and equally variant ideas have been used in marine zoology. Many studies in marine ecology have been based on Möbius' concept of the biocoenosis, or on Petersen's use of dominant or conspicuous index species, with added theoretical notions which apparently originated in plant ecology. New evidence is presented that some marine benthic communities may be characterized in terms of dominants while also allowing analysis as parts of continua of distribution along gradients. In addition, although stability usually increases as communities evolve, some types are intrinsically unstable because of the activities of the organisms themselves, rather than because of changes in the physical environment alone.Because there are different kinds of marine "communities" a single rigorous definition seems impossible. A definition is proposed which avoids theoretical suppositions about community dynamics to allow the variety of phenomena in community relations to be investigated in a relatively unbiased way.

ISSN:0706-652X    

DOI:10.1139/f69-132

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The essential feature of a stream is the continuous flow of water, and the various schemes of classification of streams and the associated fish fauna are largely based on factors which determine the average velocity. These schemes have been better developed in Europe than elsewhere, probably due to the relative uniformity of the climate. The characteristic features of fish inhabiting the more rapid streams can be related to the constraints imposed by this environment, and particularly by the need for the population to maintain its position against the continuous tendency of the stream to transport it downstream. Physiological factors associated with the normally high oxygen level and the need for continuous activity include a high routine metabolic rate, a high oxygen threshold for full activity, and, possibly, a high lower lethal limit for dissolved oxygen. Adult fish maintain their position either by continuous swimming in midwater, and these usually have a streamlined shape which is circular or laterally compressed in cross-section, or by avoiding the current and living closely attached to or in the substrate and these are usually dorso-ventrally depressed. The eggs are usually protected from the current by burying them in the substrate, sometimes in a well-developed nest. The general absence of vegetation in rapid streams results in the fish generally feeding principally on the available animal food, usually small invertebrates taken either in the drift or off the bottom. The solitary territorial behaviour which characterizes most stream-living fish probably leads to more even distribution and more efficient utilization of the food supply.

ISSN:0706-652X    

DOI:10.1139/f69-133

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The presence of possible migration routes between the Missouri (Gulf of Mexico) and adjacent Saskatchewan (Hudson Bay) drainages is briefly discussed in regard to postglacial dispersal of freshwater fishes. A checklist of 9 families and 27 species of fish recorded from the Milk and Frenchman rivers of Alberta and Saskatchewan is provided. Two of these are new to the Missouri ichthyofauna of Canada and definite records of 10 species are reported for the first time from the Missouri drainage of Saskatchewan. Notes are included on the distribution of all known species within the Missouri drainage of Canada. The possible presence of three additional species is discussed.

ISSN:0706-652X    

DOI:10.1139/f69-134

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The histology of the accessory boring organ of the naticid clam drillPolinices lewisi(Gould) was investigated by means of electron microscopy and standard histological techniques.The organ consists of two distinct epithelial regions, one producing typical mucin histochemical reaction and a central region which secretes a proteinaceous substance. Overlying the central epithelium is a brush border consisting of numerous microvilli passing through a matrix of protein and chitin.

ISSN:0706-652X    

DOI:10.1139/f69-135

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Paired fecal samples and peritoneal washes were taken from 300 18-month-old brook trout for determining their relative value in detecting IPN virus. The testing of feces revealed 14 times as many carriers as were found by peritoneal washes. Initial examinations showed at least 63% of the fish to be carriers of the virus, but 30% more were detected in four additional tests. Fecal output of virus from 37 fish was quantified up to five times during a period of 7 months which included the spawning season. Although there were exceptions, fish with high outputs of virus tended to maintain that level, and low titer carriers tended to yield small amounts, and in some instances, no virus. Tests of fecal extracts which were pooled from 5, 10, and 15 fish showed that virus was readily detected in all three. For economy and efficiency, the use of 10- or 15-sample pools is recommended for determining the presence of IPN in fish.

ISSN:0706-652X    

DOI:10.1139/f69-136

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Recent collections ofOcca verrucosaprovide new records for the species in Canada. Terminology for the ridges of bony plates on the bodies of Agonidae is standardized, and a method for enumerating plates is described and illustrated. Several meristic characters of the northern specimens exceed previously published values for the species.

ISSN:0706-652X    

DOI:10.1139/f69-137

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Overwinter survival of brook trout (Salvelinus fontinalis) from the 9-month-old fingerling stage to the 16-month-old yearling stage varied from 35 to 73% during 11 successive winters (1954–65). Mean survival through these first winters of life was 54%.Survival appeared to be independent of fingerling density most winters, and especially when September densities were less than 2200/km, as they were during 7 of 11 years. Overwinter survival tended to increase with an increase in mean length of fingerling stocks (r = 0.83++) and with an increase in winter water temperatures. Intraspecific predation did not appear to be a critical mortality factor. The survival advantage of increased fingerling size was probably related to increased physiological resistance to temperature-associated stresses rather than reduced vulnerability to predation.

ISSN:0706-652X    

DOI:10.1139/f69-138

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Collections were analysed from the three basins of the lake in 1957, and from the middle basin of the lake and a fertilized polyethylene column in 1962. The abundant copepod,Pseudocalanus minutus, was basically annual in life cycle, spawning a number of almost synchronous broods (egg sacs) in the short period of abundant food supply in early summer. The number of young per brood was dependent on size of females, and the number of broods was independent of the amount of food during the reproductive season. The species was concentrated in rich food supply at the halocline and at depth. There was no diurnal vertical migration in summer, but ontogenetic descent of older stages appeared adapted to "seeking" colder water. The species is much smaller in the lake than in the nearby sea, and this, as well as seasonal size changes, can be attributed to temperature effects. Females, but not males, roughly doubled weight ("Brooks' Law") between stages in constant conditions. Maximum development rate was about 0.4 stages/day at 6–7 C, similar to laboratory estimates reported for temperate populations. Growth is not isometric;P.minutusgrows stouter as it grows longer. Net production (some 30% as eggs) ranged from 410 to 510 mg C/m2per year in various basins and years, and was less than doubled in the fertilization experiment.The copepodOithona similiswas strictly annual and produced almost synchronous broods (two egg sacs), which were successfully recruited only in late summer, on different food requirements from those ofP.minutus. It was nonmigratory in summer, and its vertical distribution, like its size, was little influenced by temperature. Weight increments were only about 50% between copepodite stages, and development between egg and adult took at least 1.2–1.6 months. Production ranged from 202 to 347 mg C/m2per year and was not increased in the fertilization experiment.The chaetognathSagitta eleganswas annual in the lake, reaching full size but suspending development during summer. Much reproduction occurred before and after the short period of successful recruitment of young, and size of new generation was proportional to the number of adults but not the abundance of food for the young present during this period. Overwinter mortality was less in the shallow outer basin than in the middle and inner basins, whereS.eleganslived below their food species. Ontogenetic ascent of young was followed by descent of older individuals, but immatures showed marked migration into the warm, food-rich halocline at night. The species was much smaller in the lake than in the nearby sea, where it is biennial. In another landlocked fiord, temperatures intermediate between those of Ogac Lake and the nearby sea thwarted a successful annual or biennial cycle by promoting maturation at an inappropriate time of year. Net production ranged from 49 to 318 mg C/m2per year; the wide range is attributable to variable numbers of spawning adults at time of recruitment.The medusaAglantha digitalehad two generations per year in the lake. Successful reproduction may have depended on abundant small particles (phytoplankton) as food for the young, but control of recruitment and subsequent survival remains obscure. Its scarcity in the outer basin may have been related to forced coexistence withS.elegans.Aglantha digitalegenerally occupied mid-depths in the water column, sinking slightly at night, its vertical distribution being little related to temperature. The species grew about four times as long in the sea outside, but the same relationship prevailed between gonad and body size. Production ranged widely between basins and years from 13 to 263 mg C/m2per year, and was not increased by the fertilization experiment.Other holoplanktonic species in the lake are treated briefly. Of these, the ctenophores (Beroesp.) may have been of some importance in production, and the copepodEurytemora americanawas opportunistically abundant and productive in the halocline in 1962. Others, including microzooplankton, added little production.Among the planktonic larvae of benthos, bivalve (mostlyMya truncata?) larvae spent a year in the plankton, as did some polychaetes. These larvae showed marked vertical migrations, especially the older ones. The larvae only achieved an estimated 13% of the production shown byP.minutusandO.similiscombined.Allochthonous zooplankters brought in by the tides seemed ill-adapted to the lake. The few surviving allochthonousP.minutusbecame smaller in the warm waters, and may have insured gene flow between the lake and the sea. The allochthonous zooplankton were important as organic enrichment, equivalent to about one-half the annual autochthonous zooplankton production.Some general conclusions follow. Niche diversification is clear in the lake, and some widespread arctic species may be excluded competitively. The marked seasonality of the lake (and other waters of middle and high latitudes) means that controls of population size and growth occur when food is in excess. The studies of vertical distribution and migration demonstrate the necessity for close vertical spacing of samples, and detailed consideration of different stages and size classes. Support is partial at best for the theory that vertical migration is adapted to control growth and development and maximize rates of increase in thermally stratified waters. The results nevertheless stress the over-riding influence of temperature on body size of zooplankters. Overall zooplankton production was about 1 g C/m2per year. "Herbivore" production was about 7% of primary production in 1962, and was little enhanced by a seven-fold increase of primary production in the fertilization experiment. Predator production ranged between 16 and 68% of "herbivore" production. Production/biomass ratios averaged about 3:1, but wide variations occurred, such that the ratios cannot be considered to be "physiological" or determinate for a species or a system. It is argued that production cannot be measured or "explained" in highly seasonal environments like Ogac Lake without detailed quantitative studies of life histories.

ISSN:0706-652X    

DOI:10.1139/f69-139

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Primary production was about 12 g/m2in the middle basin of Ogac Lake during 1962. Production was limited by available N, probably largely by amount of nitrate available at the end of winter. Production was largely concentrated in narrow strata — one descending from near the surface in June to occupy nutrient-rich deep water in summer, and another developing at the halocline in summer, possibly sustained by nutrients from freshwater kill of the littoral biota in 1962.Polyethylene columns, 1 m in diameter and 30.5 m long, were set between the fresh surface and anoxic depth of the middle basin in 1962. A four-fold increase of nitrate and a two and a half-fold increase of phosphate led to a parallel uptake of the two nutrients in the columns, and to an approximately five-fold increase in mean amount of chlorophyll and a seven-fold increase in primary production compared with the lake during the period of the fertilization experiment.

ISSN:0706-652X    

DOI:10.1139/f69-140

出版商:NRC Research Press    

年代:1969

数据来源: NRC