摘要:

A stratified random sample of macrobenthos in Western Port (Victoria, Australia) provided adequate data to take an a posteriori look at the efficiency of various random survey designs in terms of their ability to provide precise estimates of the mean number of individuals per taxon, i.e. mean estimates with the smallest possible variance. Emphasis was placed on the efficiency of the stratified simple random sampling design. The analyses showed that bay-wide estimates resulting from various stratified designs would not have been substantially more precise than those from simple random sampling. This conclusion was not influenced by the allocation strategy used in the stratified design. On the other hand, substantial gains in precision could have been made,for the same total number of grab samples, by increasing the number of stations at the expense of the number of grab samples per station. Our data suggested that the optimal number of grab samples per station is only one, contrary to the common practice of multiple grab samples per station.Key words: stratified, random, survey, optimal, macrobenthos, sample, Western Port

ISSN:0706-652X    

DOI:10.1139/f79-054

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The electivity indicesEiandEi′ of predator–prey interaction are currently used to quantify particle-size selection by grazers. Under conditions of passive, mechanical particle-size selection predicted by the leaky-sieve model, these indices yield electivity vs. particle-size curves that vary with the shape of the particle-size spectrum of food offered to the zooplankton. In addition to this bias, poor estimates of electivity will be obtained unless only a small fraction of the food is eaten in such experiments. The selectivity coefficient (Wi) used by modelers in feeding constructs and the electivity indexEi*, derived here, are recommended instead because they do not suffer from the shortcomings described forEiandEi′. Moreover, use ofWi′s andEi*'s is recommended for quantifying selection for many other cases of predator–prey interaction.Key words: electivity indices, selectivity, selective grazing, predator–prey intraction

ISSN:0706-652X    

DOI:10.1139/f79-055

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Body temperatures of rainbow trout (Salmo gairdneri) caught from a thermal discharge into Lake Michigan were used to determine selected temperatures and to estimate acclimation temperatures of this species under field conditions. Approximately 65–75% of the variability in body temperatures was related to water temperature (direct) and fish weight (inverse). Body temperatures increased with increases in discharge temperature, but the difference between body and ambient water temperatures decreased at high water temperatures. The modal body temperature of small fish was 19 °C, the final preferred temperature predicted for rainbow trout by some lab studies. The modal body temperature of large fish was 15 °C. Estimates of acclimation temperatures indicate that the majority of rainbow trout caught in this discharge area were acclimated to plume temperatures. Estimated acclimation temperatures exceeded ambient acclimation by as much as 10 °C for individual fish while group means ranged between 2 and 6 °C over ambient acclimation.Key words: temperature selection, acclimation, thermal plume, rainbow trout, Lake Michigan, body temperature, size effect

ISSN:0706-652X    

DOI:10.1139/f79-056

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A method using otoliths is presented for the age determination of yellowtail rockfish (Sebastes flavidus). Most of the details of this method are applicable to other species of rockfish. The method is validated in younger fish by documenting growth of the otolith annular zone by month, and by comparison with ages read from scales. Further validation is provided by length-at-age data, which show monotone growth for both males and females. Age reader variability was analyzed for each age category using random effects analysis of variance. This analysis showed that within-reader variances were similar for the two readers. Although there were significant variance components due to between-reader differences for aging some age categories, the contribution of this variance component to total variability was negligible. The standard deviation for an age determination of an otolith was similar for both readers, ranging from about 0.6 at 8 yr to about 1.6 at 19 yr. For both readers, the coefficient of variation was approximately 0.08 at all ages.Key words:Sebastes flavidus, age determination, otoliths

ISSN:0706-652X    

DOI:10.1139/f79-057

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Three hypotheses regarding the movement patterns of the British Columbia salmon purse-seine fleet are considered. Two of these hypotheses, that boats move strictly in traditional patterns, or that boats attempt to maximize weekly landed value of catch are rejected. The third hypothesis, that boats move to optimize economic gain, modified by relative desirability of the areas appears to provide a better prediction of patterns. It is shown that when unusually large runs occur in an area, a sufficient number of boats will move into that area to reduce the catch per boat to a level typical of that area.Key words: boat movement, fleet dynamics, spatial pattern

ISSN:0706-652X    

DOI:10.1139/f79-058

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Consumption of three species of prey by brown trout (Salmo trutta) in a laboratory stream was studied during 7-d experiments. Two drift rates (5 and 10 organisms/min) and three ratios (1:1, 2:1, 5:1) of small:large alternative prey were employed. Responses to prey species stabilized after 4–6 d and 800–1200 prey captures, but no prey was completely excluded from the diet. Size-selective predation was a dominant characteristic of the response. The fish appeared to alter the area (depth) searched in response to prey density; electivity was greatest when prey densities were high. Disproportionate predation on abundant prey ("switching") was a temporary phenomenon, which may have been masked by prey size. Brown trout ultimately achieved 54–91% of a hypothetical diet in which prey are ranked in order of size (energy content). Deviations from an optimal diet may be explained in terms of a feeding strategy that deals with heterogeneous distribution of prey, as well as with the behavioral capabilities of the predator.Key words: behavior, fish, invertebrate drift, optimal foraging, predation, prey size and abundance, Salmonidae, search image, streams

ISSN:0706-652X    

DOI:10.1139/f79-059

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Sensitivity analysis has been used to estimate the relative importance of input parameters both between and within two harp seal (Pagophilus groenlandicus) population models. The population size at maximum sustainable yield is shown to be much more poorly defined than the yield level itself.Key words: sensitivity analysis, harp seal, population model, sustainable yield, management

ISSN:0706-652X    

DOI:10.1139/f79-060

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Chronic toxicity values were developed forDaphnia magnawith six surfactants and a detergent builder, each selected on the basis of previously existing chronic fish test data. Predictive correlations were examined for testing end points between 21-dDaphniachronics and 1-yr fish chronics to provide a short-term alternative chronic test species while developing toxicity data for an intermediate trophic level species. For the detergent materials tested, a strong correlation (r = 0.98) exists betweenDaphniaand fish no-effect concentrations. A replacement term, NOEC (no observed effect concentration), is suggested to clarify interpretive ambiguities associated with the definition of the MATC (maximum acceptable toxicant concentration) value. Additional chronic toxicity data from the current literature for these two test species and several test substances representing metals, polychlorinated biphenyl isomers, and pesticide formulations were similarly compared. A correlation analysis demonstrated an overall Pearson correlation coefficient of 0.79 for these data. Although significant outliers were evident from this correlation, these differences may be due primarily to differences in modes of toxic action of these test substances. The relatively short life cycle and 21-d duration of the test, small water volumes, ease in handling, high fecundity, and good correlation of 21-d chronic data with chronic fish toxicity data makeDaphniachronic tests an attractive alternative to the conduct of longer term fish tests.Key words:Daphnia,Pimephales promelas, toxicity tests, chronic, mortality, surfactants, metals, pesticides

ISSN:0706-652X    

DOI:10.1139/f79-061

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Since the mid-19th century, numerous attempts have been made to restore or enhance populations of the Atlantic salmon,Salmo salar, within the endemic range, and to establish the species in other parts of the world. Despite all efforts, salmon have become naturalized locally only in eastern North America, Argentina, the Faeroe Islands, and New Zealand. Principal factors affecting the disappearance, restoration, or naturalization of populations are water temperature and availability of suitable spawning and nursery sites. Commercial exploitation of the species in coastal and offshore waters is viewed internationally as a factor of increased importance in the numerical regulation of river spawning runs. A further expansion of the world distribution of Atlantic salmon by naturalization seems unlikely except in areas where preliminary plantings have been made or brood stocks are presently held. Atlantic salmon produced by commercial sea farming operations in Norway, Scotland, Spain, and France are considered to be of comparable quality to fish harvested from the wild. Also, there is presently interest in the potential of sea ranching of Atlantic salmon.Key words: zoogeography, endemic range, naturalized range, artificial propagation, environmental impact, exploitation, aquaculture

ISSN:0706-652X    

DOI:10.1139/f79-062

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A relatively simple and reliable in vitro method for marine fish chromosome study was developed. The addition of 10% chick embryo extract to serum-supplemented Eagle's minimum essential medium with high concentration of NaCl resulted in marked growth of kidney cells in the marine conger eel (Astroconger myriaster) after activation by phytohemagglutinin (PHA). Culture medium without chick embryo extract or PHA and/or with normal concentration of NaCl did not induce substantial growth. In contrast to reports by others, humidified culture was not required for excellent cell growth of these teleost kidney cells. Numerous metaphases unmarred by overlapping chromosomes were recovered and excellent karyograms were available for detailed karyotype analysis.Key words: kidney, culture, marine fish, chromosome

ISSN:0706-652X    

DOI:10.1139/f79-063

出版商:NRC Research Press    

年代:1979

数据来源: NRC