摘要:

A comparison was made between the procedure of factoring variables before using them in discriminant analysis and the usual procedure of using the original variables in discriminant analysis. The results indicated factoring seven scale measurements on sockeye salmon (Oncorhynchus nerka) with varimax rotation produced four new variables which gave more valid results in classifying sockeye salmon by area of origin than the original variables when discriminant functions were computed. Although the results on the basic data from which the functions were derived were not as good using the four factor scores as the seven original variables, the accuracy of classification was much more consistent in the test data with the factor scores. The loss in accuracy was at leasttimes as great for functions based on the original variables as for ones based on factor scores. The errors in classifying fish to their individual places of origin were perhaps too large for the procedure to be useful in the field, but the accuracy of classification to the British Columbia or Alaska region was quite high.

ISSN:0706-652X    

DOI:10.1139/f74-001

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Blood constituents were measured in salmon (Oncorhynchus gorbuschaandO.nerka) at various times during the spawning migration. Values for blood sodium, potassium, calcium, glucose, protein, and hematocrit suggested that during early stages of migration through post-spawning these fish experience a syndrome reminiscent of mammalian hypoadrenocorticism. The reverse was true of fish in advanced stages of senescence. Older fish also suffered ascorbate deficiency with a resultant necrosis of the skin. This deficiency was corrected by intraperitoneal injection of ascorbate. Various forms of hormone therapy applied to senescent fish were unsuccessful in prolonging their life appreciably.

ISSN:0706-652X    

DOI:10.1139/f74-002

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

An effective sequential procedure for recovery ofMyxosoma cerebralisspores from infected trout was developed, and quantification of spores was carried out at each step of release and concentration. Methods are described for fresh and frozen material. Effective concentration of from 1100- to 9000-fold and an estimated efficiency of recovery of about 80% has been achieved. Tabular and graphic data are presented with recommendations for diagnostic applications. The immediate applications of these procedures are in implementing more effective detection and in preparing antigen for the immunologic studies that should provide the most sensitive detection.

ISSN:0706-652X    

DOI:10.1139/f74-003

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Cruises were conducted off the northern Washington coast each year during 1967–72 to study trends in the availability and biological characteristics of Pacific Ocean perch (Sebastes alutus).There were marked differences in catch rate between cruises, and corresponding differences in age composition and age–length structure indicated that they resulted from differential availability of an old, slow-growing segment of the population to on-bottom trawling. Females from this segment of the population were particularly available when the cruise coincided with the period of peak spawning, and both sexes were available during the 1972 summer cruise.Within cruises, adults from different portions of the bathymetric range showed similar age composition, but there was an inverse relationship between depth and size attained by age 15. Size compositions consequently contained a smaller proportion of large fish as depth increased.Juveniles were confined to the shallow portions of the bathymetric range. There were obvious between-year changes in the length and age composition of juveniles, caused by the temporal progression of a dominant 1961 year-class.Fluctuations in availability make it difficult to monitor changes in mortality and since age composition also varies with availability, the problem is compounded further. Unless all segments of the population are located and sampled in proportion to their abundance, estimates of mortality can be made only between those cruises where the old, slow-growing component of the population is equally available.

ISSN:0706-652X    

DOI:10.1139/f74-004

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The hypothesis that developmental plasticity contributes to variation in swimbladder length, volume, weight of tissue, and buoyancy was examined in two species of dace. At both maximum and minimum buoyancy attained dace reared in still water to adult size possessed swimbladders of a greater length, volume, and weight of tissue than those reared in current. Such developmental plasticity affected the range over which buoyancy could be adjusted (behavioral plasticity). Those reared in still water attained a more buoyant condition than those reared in current while the latter attained a greater degree of negative buoyancy.

ISSN:0706-652X    

DOI:10.1139/f74-005

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Lepeophtheirus cuneifersp. nov. (Copepoda: Caligidae) is described and illustrated. This copepod is a parasite of marine fishes off the coast of Alaska, its hosts includingRaja binoculataandHexagrammos lagocephalus. Other possible hosts areLeptocottus armatusandTheragra chalcogramma.

ISSN:0706-652X    

DOI:10.1139/f74-006

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

White suckers (Catostomus commersoni) in the acidic Lumsden Lake in 1967 and 1968 exhibited reduced annual growth followed by death. The reduced growth and death appeared directly related to the lowpH and not to a shortage of food caused by the decreasingpH.

ISSN:0706-652X    

DOI:10.1139/f74-007

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Adult lake whitefish (Coregonus clupeaformis) from Clearwater Lake and second generation adults of offspring from Clearwater whitefish transplanted to Lyons Lake were compared with respect to morphometric and meristic characters and isozymes of L-glycerol-3-phosphate dehydrogenase (GPDH). Feeding habits and abundance of pelagic and benthic foods were compared in the two lakes.Gill raker number, lateral line scale count, and interorbital width remained constant between parental and offspring populations. Gill raker length was the main character found to differ between the populations. This was found to be related to the percentage and type of benthic food eaten. Abrasion of the gill rakers is offered as an explanation for the differences in gill raker length. Differences were found in various other meristic and morphological characters, as well as in electrophoretic phenotype frequencies of isozymes of GPDH.

ISSN:0706-652X    

DOI:10.1139/f74-008

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The mineral content of scales, metals only, was studied. Fish of theCatostomus commersonisubspecies were used, taken from a healthy environment, (the Manicouagan River) and an environment polluted by, among other substances, various metals (Rivière des Prairies, near Montréal). X-ray microspectrometry was combined with electron microprobe scanning techniques, with subsequent microdensitometric scanning. Scales contained, in addition to the highly predominant calcium, the following: Na, Mg, Al, K, Fe, Cu, Zn, and Ba, as well as some Cr, Mn, Co, Ni, Sr, Ag, Cd, Cs, Hg, and Pb. All metals were between the circuli in the osteoid structures. The latter category of metals, widely known for their toxicity, were more abundant in the scales of the sample from polluted waters, whereas the reverse was true for the other metals, with the exception of Al and Ba, which were found in equal quantities in both samples. If the difference in content of the scales taken from fish of the two different environments is seen in relation with the fact that the toxic metals are more abundant in polluted waters and the fact that there is the possibility that excess metal from the water can replace calcium in the scales, we may infer that the mineral content of scales is related at least in part to that of the surrounding aquatic environment.

ISSN:0706-652X    

DOI:10.1139/f74-009

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The daily values of137Cs intake by bluegill (Lepomis macrochirus) from a small impoundment receiving low-level radioactive effluents were used to calculate the daily feeding rates of the fish. The calculations of137Cs intake, for a nonequilibrium state, were based on fish growth, the seasonal fluctuation of137Cs concentration in fish, and the temperature-elimination rate relationship. The feeding rates were obtained by dividing the daily intake of137Cs by the concentration of137Cs in the diet. The daily meal of bluegill varied from 0.8% of body weight in February to 3.2% in June with an annual mean of 1.75%. There was a positive correlation (r2 = 0.805) between the daily meal and the daily temperature. The ecological growth efficiency was 4.2% during the period from April to October.

ISSN:0706-652X    

DOI:10.1139/f74-010

出版商:NRC Research Press    

年代:1974

数据来源: NRC