摘要:

Field and laboratory studies of the feeding and association of the gammarid amphipodEogammarus confervicoluswith algae and vascular plant debris were conducted on jetties, marshes, and sandflats at the Fraser River Estuary. Associations withPrasiola meridionalis(alga), and debris fromCarex lyngbyei(vascular plant) were statistically significant. Vascular plant debris was more widespread in winter (January) compared to a summer survey (August). Laboratory growth rates and survival varied with food types, which were ranked (best to worst) as follows:Enteromorpha linza,Pylaiella littoralis,Porphyraspp.,Navicula grevillei,Carex lyngbyeidebris andUlva lactuca. Assimilation efficiencies, measured with gravimetric and radioisotope techniques (14C) ranged from about 78% withP.littoralisto 62% withU.lactuca. Construction of jetties could increase the surface area for algal growth, but there would be no appreciable enhancement of primary production compared to a natural marsh/sandflat ecosystem.Key words: Crustacea,Eogammarus confervicolus, benthic algae, Fraser Estuary, intertidal distribution, feeding, ecological associations, engineering structures

ISSN:0706-652X    

DOI:10.1139/f80-001

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The abundance of 12 year-classes of yellow perch (Perca flavescens) in Oneida Lake, New York, was estimated at intervals between ages 0 and II from catch and area swept by trawls. Rankings of abundance of year-classes changed between the ends of the first and third growing seasons, suggesting that ultimate year-class strength was influenced strongly by mortality of age I and II fish. Predation by walleyes was probably the principal cause of mortality of age I and II perch. Although frequency of occurrence of age I and II perch in stomachs of walleyes was low, several lines of evidence suggested that density of juvenile perch also was low and that walleyes consumed a large proportion of each perch cohort. Rates of mortality were modified by perch length, perch density, and density of age 0 perch, all of which relate to intensity of walleye predation.Key words: yellow perch, walleye; mortality, predation; Oneida Lake

ISSN:0706-652X    

DOI:10.1139/f80-002

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Betapista dekkerae, new genus and new species, is described. The generic diagnoses forLaphaniaandScionidesare improved after inspection of the holotypes of the type species.Eupolymnia heterobranchia(syn.,E.crescentis) is redescribed. Additions to the descriptions, based on study of type material, are made forLaphania boecki(new record, Northeast Pacific),Neoamphitrite robusta(syn.,Scionides dux),Neoleprea californicaandN.spiralis,Pista brevibrunchiata(new record, British Columbia [B.C.], Washington [WA], Japan) andP.fratrella, andPolycirrus californicus(new record, B.C., WA, syn.,P.perplexus). Other additions to the descriptions are provided forAmaeana occidentalis(new record, B.C.) andPista cristata. Two furtherPistaspecies (one from the Skagerrak) and fivePolycirrusspecies are charcterized but not named. Other new records areLanassa venusta venusta(B.C.),Lysilla loveni, andNeoleprea japonica(the two latter for Northeast Pacific).Lysilla pacifica,Pista fasciata, andP.fratrellaare shown not to be members of the fauna of British Columbia and Washington. Presumably, neither isPolycirrus caliendrum. New observations on the types of the AntarcticPolycirrus kerguelensisandEreutho kerguelensisare noted.Key words:Betapistan.g.,Neoleprea, new records, Northeast Pacific,Pista,Polycirrus,Scionides, Terebellidae

ISSN:0706-652X    

DOI:10.1139/f80-003

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Ripening ovaries of Pacific hake from the Strait of Georgia contained several size-classes of oocytes. Only those from the group of the largest yolked oocytes became hydrated and were eventually released to be fertilized. Examination of ovaries from recently spawned fish showed that smaller, residual yolked oocytes were being resorbed. Yolked oocytes not released at spawning may represent a potential for an increase in fecundity of Pacific hake in the Strait of Georgia. The failure of some developing oocytes to be released suggests that traditional methods of estimating fecundity will not accurately estimate the number of gametes produced by each female. Cytological observations suggested that the number of potential oocytes is not fixed at first maturity.Key words: Pacific hake, fecundity, oocytes, spawning, Strait of Georgia

ISSN:0706-652X    

DOI:10.1139/f80-004

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A recently initiated ichthyoplankton survey of the Scotian Shelf has discovered large numbers of subtropical/tropical expatriated fishes, mostly larvae, and at least two previously unrecognized populations. Thirty-three species in 25 primarily subtropical families (Carcharhinidae, Engraulidae, Synodontidae, Chlorophthalmidae, Ogcocephalidae, Antennariidae, Carapidae, Ophidiidae, Exocoetidae, Syngnathidae, Scorpaenidae, Triglidae, Dactylopteridae, Serranidae, Apogonidae, Branchiostegidae, Rachycentridae, Sciaenidae, Labridae, Scaridae, Callionymidae, Gobiidae, Bothidae, Cynoglossidae, and Ostraciontidae), seven species in four deepwater families (Gonostomatidae, Sternoptychidae, Myctophidae, and Moridae) and two gadoids are reported as new or rare records from the Canadian Atlantic. The frequency and quantity of subtropical expatriates raise the question of their ultimate fate. The existence of eastern Atlantic populations of some of these raises the possibility of transatlantic dispersal. Juvenile or adult specimens of most of the expatriated forms have not been found on the Scotian Shelf but the complex hydrography on the shelf may allow temporary habitation especially in summer. Two species, red hake and Gulf Stream flounder, appear to have discrete, self-sustaining populations on the Scotian Shelf. Both species appear to represent northernmost populations which may be living near their lower thermal limit. Discrepancies between the literature on red hake and data reported herein are unresolved and require long-term observations.Key words: Scotian Shelf, ichthyoplankton, hydrography, zoogeography, western North Atlantic

ISSN:0706-652X    

DOI:10.1139/f80-005

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Examination of morphometric and meristic characteristics of Atlantic herring (Clupea harengus harengus) caught during spawning along the Gaspé coast and the St. Lawrence Estuary lead to the conclusion of the existence of at least three herring populations in that area. The first one occurs in the St. Lawrence Estuary, spawns in the spring and is characterized by smaller length-at-age values than the two other populations which are comprised respectively of spring-spawners and autumn-spawners that are fished off the Gaspé peninsula.Key words: Atlantic herring, St. Lawrence Estuary, Gaspé peninsula, morphometric characteristics, meristic characteristics

ISSN:0706-652X    

DOI:10.1139/f80-006

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A new analysis of hypolimnetic oxygen in Central Lake Erie indicates that historic increases in the apparent depletion were not as great as formerly believed. The differences that did occur were mostly related to variations in hypolimnion thickness. Changes, if any, in the oxygen depletion rate due to eutrophication are as yet too small to be recognized. Present-day oxygen depletion rates, when corrected for the relatively high temperatures in Lake Erie, are within the range thought to be indicative of mesotrophy in small lakes. The general level of oxygen depletion observed in the Central Basin of Lake Erie is expected on the basis of morphology alone.Key words: Lake Erie, oxygen, hypolimnion, oxygen depletion, trend

ISSN:0706-652X    

DOI:10.1139/f80-007

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Preservation of the genetic characteristics of a population is one of the primary objectives of many fish stocking programs. Using starch gel electrophoresis we have tested for temporal gene frequency stability at two polymorphic loci coding for α-glycerophosphate dehydrogenase and creatine phosphokinase. Three Swedish hatchery stocks of brown trout (Salmo trutta) and field samples from natural populations corresponding to two of these stocks were analyzed. Highly significant allele frequency changes at both loci indicated considerable lack of intra-stock genetic homogeneity. In the light of these findings we emphasize the importance of using large numbers of actual as well as effective parents to avoid inadvertent genetic changes and inbreeding. No stock should be founded or perpetuated using less than approximately 30 parents of the least numerous sex in any generation.Key words: inbreeding, genetic drift, gene bank, electrophoresis, stocking, trout

ISSN:0706-652X    

DOI:10.1139/f80-008

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The gut of the sea urchinStrongylocentrotus droebachiensishas between 2 × 108and 6 × 109bacteria/mL of gut contents. When these bacteria are present, radioactive carbon fed to the urchins as either glucose or cellulose appears in all of the protein amino acids of the gonads. However, when the gut flora is suppressed by a mixture of antibiotics, injection of the sea urchins with radioactive glucose results in the labeling of some of the amino acids (nonessential amino acids) but not others (essential amino acids). These results imply that: (a) sea urchins have the ability to digest cellulose, probably with the aid of the gut flora; (b) intestinal microorganisms can synthesize essential amino acids; and (c) amino acids of microbial origin are available to the sea urchins. The amino acid compositions of (i) kelp (Laminaria longicruris), (ii) sea urchin intestinal microflora, and (iii) sea urchins, were determined over a yearly cycle. The amino acid composition of kelp and microbes were compared as a source of nutrient for the sea urchins, using as indications: overall similarity in compositions, essential amino acid index, and percentage of total amino acid that is essential. All three comparative methods show that the microbial protein is of higher nutritive value than the kelp protein.Key words: amino acids, nitrogen, bacteria, kelp,Laminaria longicruris, sea urchin,Strongylocentrotus droebachiensis

ISSN:0706-652X    

DOI:10.1139/f80-009

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A model is developed (i) to integrate a set of experimental observations concerning the energy flow through the amictic female rotiferBrachionus rubensEhrbg.; (ii) to identify inconsistencies in the data; (iii) to understand better the energy dynamics of this organism and the impact of the environment on it; and (iv) to determine the direction of further experimental and theoretical studies. Simulations of energy flow through this organism are generated for various concentrations of food (the algaChlorella vulgaris), constant during its life span. It is shown that the experimental data for the immature female are self-consistent but that the experimental instantaneous values of total production for the mature female are undervalued. Consequently, Pilarska's instantaneous values of food assimilation and the instantaneous coefficients of energy conversion efficiency are undervalued for the mature female. Using sensitivity analysis we find that the model is highly sensitive to changes in (listed in order of importance) (i) the instantaneous value of food consumption, (ii) the instantaneous coefficient of food assimilation efficiency, (iii) the life span, and (iv) the egg calorific value. The model is relatively insensitive to changes in (i) the initial body calorific value, (ii) the age at maturity, (iii) the time interval between two successive acts of reproduction, and (iv) the instantaneous value of respiration. Specific parameters are identified as needing remeasurement.Key words: model, simulation, bioenergetics, growth, reproduction, rotifer,Brachionus rubens, sensitivity

ISSN:0706-652X    

DOI:10.1139/f80-010

出版商:NRC Research Press    

年代:1980

数据来源: NRC