摘要:

The Schaefer production model is converted to a form directly applicable to a data stream of annual fishing efforts and catches. The new version is also stochastic; that is, it allows for unpredictable influences on the fishery. A new method for estimating optimum effort and catch results from this analysis, as well as a way of measuring uncertainty in these estimates. Equations are given for predicting the next annual catch and assigning confidence limits to this prediction. Linear and nonlinear regressions are proposed for this analysis, and the relationship between them is rigorously demonstrated. The linear method leads to estimation formulas simple enough to be applied on a programmable pocket calculator.Key words: Schaefer model, production model, stochastic model, management, fishing effort, catch per unit effort, maximum sustainable yield

ISSN:0706-652X    

DOI:10.1139/f77-094

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Gametogenesis and gonadal index undergo an annual cycle with minima in September and maxima in May for a population of red urchins,Strongylocentrotus franciscanus, from southwestern Vancouver Island. Postspawning recovery is rapid and there are no significant differences between male and female gonadal indices, but a small gonad to body-size correlation is evident. Gonadal index is not the product of gametogenesis, but is correlated to glycogen accumulation which may reach 13% gonad total weight. The fishing season for roe in southern British Columbia extends from October to April with several weeks variability depending on local conditions and weather. Yields constitute up to 25% total drained weight.Key words: urchins, fishery, gametogenesis, glycogen, hermaphroditism, sex ratio

ISSN:0706-652X    

DOI:10.1139/f77-095

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A study to determine the prevalence of fish disease in the Bering Sea revealed lymphocystis disease in yellowfin sole (Limanda aspera). The gross pathology and histopathology of typical nodules are described. Electron microscopic studies revealed characteristic icosahedral lymphocystis virus particles, as well as clusters of intracellular structures of uncertain origin. This study begins a larger effort to understand the effects of an altered marine environment upon the biology of lymphocystis virus infection in the Bering Sea.Key words: lymphocystis, pleuronectids, yellowfin sole, Bering Sea, flatfish.

ISSN:0706-652X    

DOI:10.1139/f77-096

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Frequencies of alleles of the genes governing electrophoretic phenotypes of lake whitefish (Coregonus clupeaformis) muscle glycerol-3-phosphate dehydrogenase (G-3-PDH) and lactate dehydrogenase (LDH) enzymes, the genetics of which were determined previously, proved useful tools for characterizing populations. Malate dehydrogenase (MDH) and hemoglobin electrophoretic phenotypes, the genetics of which have not been determined, proved useful only for discerning differences among large groups of populations. Using all these characters we determined postglacial routes of gene flow among western Canadian lake whitefish populations and related the biochemical data to the glacial refugia in which lake whitefish are believed to have survived the Wisconsin glaciation. Apparently most lake whitefish populations west of the Ontario–Manitoba boundary and east of the Rocky Mountains were derived from a Mississippi refugium stock with some input from the Bering refugium. At an early stage in the mixing of the two stocks, headwaters of the Peace, Athabasca, and Mackenzie rivers and the Fraser River system were invaded. Subsequently, these areas were cut off from mainstem rivers of the plains, and a G-3-PDH allele not found in early emigrants from the Mississippi refugium appeared and spread throughout the major river systems of central Canada. No evidence was found that any Mississippi stock lake whitefish were able to invade the upper Liard River and Yukon River system including the area of the Bering refugium. Bering stock lake whitefish probably emigrated from that refugium by way of headwater transfer from the Yukon River to the Liard River and possibly, by way of the Porcupine and Peel rivers, from the Yukon River to the lower Mackenzie River. Routes of postglacial dispersal suggested by geological information, rather than selection, appear to provide adequate explanations for the distributions of the biochemical characters in present day lake whitefish populations. This explanation of the biochemical data is also in accord with the distribution of modal gillraker counts in lake whitefish populations and also with the distribution of other freshwater fishes in western Canada.Key words: fish, lake whitefish,Coregonus clupeaformis, salmonidae, zoogeography, dehydrogenase, postglacial, biochemical genetics

ISSN:0706-652X    

DOI:10.1139/f77-097

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

On June 4, 1974, the Athabasca River was treated with methoxychlor for control of blackfly larvae. Pesticide was introduced into the water in a manner calculated to generate a 15-min pulse of treated water containing 300 μg methoxychlor/ℓ. A preliminary experiment with rainbow trout (Salmo gairdneri) indicated that liver or kidney residues of methoxychlor would be suitable for monitoring likely times and places to expect toxic effects on fish in the river. Fish (Salmo gairdneri,Catostomus commersoni,C.catostomus, andHybopsis gracilis) were caged in order to observe residues and mortality. Caged fish were not killed by methoxychlor but they contained lower liver residues than wild fish of the same species captured near cages. Contaminated wild fish were found upstream of the treatment site after treatment. Residues were below detection limits by June 16. Residue measurements suggested that the most likely times to expect fish poisoning were the 2 wk following treatment and that the most likely places were those river areas extending a few kilometres in both directions from the point of application. Evidence of fish movements and low pesticide residues in caged individuals reduced confidence in residue methods as monitoring tool

ISSN:0706-652X    

DOI:10.1139/f77-098

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

At a controlled food intake level after 14 days at a given feeding regime, the liver–somatic index (liver weight as a percentage of body weight) of largemouth bass,Micropterus salmoides, was positively correlated with daily food intake. At temperatures of 20.0 and 28.0 °C there was no overlap in the ranges of the liver–somatic index of bass fed 0, 2, and 4% of their body weight in live green sunfish (Lepomis cyanellus) per day. Within a given feeding regime, increased temperature lowered the liver–somatic index.

ISSN:0706-652X    

DOI:10.1139/f77-099

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Specific growth and mortality rates of juvenile rainbow trout (Salmo gairdneri) were determined for 50 days at seven constant temperatures between 8 and 22 °C and six diel temperature fluctuations (sine curve of amplitude ±3.8 deg C about mean temperatures from 12 to 22 °C). For constant temperature treatments the maximum specific growth rate of trout fed excess rations was 5.12%/day at 17.2 °C. An average specific mortality rate of 0.35%/day was observed at the optimum temperature and lower. At temperatures in excess of the growth optimum, mortality rates were significantly higher during the first 20 days of this experiment than the last 30 days. The highest constant temperature at which specific growth and mortality rates became equal (initial biomass remained constant over 40 days) was 23 °C. The upper incipient lethal temperature was 25.6 °C for trout acclimated to 16 °C. A yield model was developed to describe the effects of temperature on the living biomass over time and to facilitate comparison of treatment responses. When yield was plotted against mean temperature, the curve of response to fluctuating temperatures was shifted horizontally an average 1.5 deg C towards colder temperatures than the curve of response to constant temperature treatments. This response pattern to fluctuating treatments indicates that rainbow trout do not respond to mean temperature, but they acclimate to some value between the mean and maximum daily temperatures. These data are discussed in relation to establishment of criteria for summer maximum temperatures for fish.Key words: constant temperature, fluctuating temperature, specific growth rate, specific mortality rate, yield, lethal temperature, zero net biomass, rainbow trout, thermal criteria

ISSN:0706-652X    

DOI:10.1139/f77-100

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The pH of Lumsden Lake was closely related to the measured amount of acid entering the lake from bulk precipitation. In 1972 it was estimated that an excess of 2135 kg of H2SO4was added to the lake from the atmosphere. The predicted annual change in lake pH was from 5.2 to 4.8 and the actual measured change was from 5.2 to 4.7. In 1973 an estimated excess of 1271 kg of H2SO4was added to the lake from the atmosphere. The predicted annual pH change was from 4.8 to 4.7 and there was no net change in the lake pH in 1973.Lumsden Lake also had high concentrations of sulfate, manganese, zinc, and nickel in comparison with remote or "unpolluted" lakes. High concentrations of manganese and possibly some zinc in the lake appeared to result from increased mobilization from the lake sediments or watershed or both as the pH decreased. Atmospheric fallout also contributed substantial quantities of nickel and copper to the watershed, some of which appeared to be retained in the lake water. The high concentrations of lead in the precipitation were not retained in the lake.

ISSN:0706-652X    

DOI:10.1139/f77-101

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A previous claim for the occurrence of antheraxanthin and the absence of typical cyanophycean xanthophylls inAgmenellum quadruplicatumhas been disproven. This phycocyanin-producing prokaryote showed chlorophylla, β-carotene, zeaxanthin, one myxoxanthophyll-like, and one myxol-like carotenoid as the major pigments. Traces of keto and other carotenoids were observed, one of which appears to be phoenicopterone or acis-echinenone. No antheraxanthin and chlorophyllborcwere detected under all culture conditions tested. Algal chlorosis from culture aging was caused by the consecutive loss of phycocyanin and chlorophyll, but the carotenoid composition was much less affected and there was no gain of secondary or keto carotenoids. We concluded that this alga is a typical member of the Cyanophyceae in terms of pigment chemotaxonomy.

ISSN:0706-652X    

DOI:10.1139/f77-102

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Through abatement of present high nutrient loadings to the reservoir and preservation of sediment integrity, we predict that eutrophic Long Lake will experience a rapid recovery after the City of Spokane, Washington, establishes an advanced wastewater treatment plant with phosphorus removal. Two sediment cores were zoned into annual layers according to profile concentrations of organic matter, nitrogen, phosphorus, and diatom frustules. Sedimentation rate was 26 mm∙yr−1between 1958 and 1973. Below the 25 mm-depth, phosphorus and diatom profiles were most obvious because clay particles, entering the reservoir during spring runoff, covered the biological material precipitated the previous year. This mechanism effectively prevents internal recycling of nutrients, particularly phosphorus, from the bottom sediments.Key words: reservoir, sediment cores, phosphorus, nitrogen, organic matter, diatom frustules, clays, internal nutrient recycling, recove

ISSN:0706-652X    

DOI:10.1139/f77-103

出版商:NRC Research Press    

年代:1977

数据来源: NRC