摘要:

Stomachs of young cod were opened at various time intervals after they had voluntarily eaten measured meals. More digested food left the stomach in the first few hours after the meal was given than towards the end of digestion. Instantaneous depletion rate increased rapidly with increase in acclimation temperature from 2 to 15 C. The rate was not increased at 19 C and was possibly depressed. Fish would not feed at 21 C. When meal size was varied, a straight-line relation was found between rate of gastric emptying and quantity of food in the stomach. This implies that in young cod intestinal absorption is coupled to food intake by regulation of the gastric volume. It is likely that digestion rate data could be used to estimate daily rations for fish in their own environment by measuring quantity of food in the stomach.

ISSN:0706-652X    

DOI:10.1139/f70-140

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

In experimental aquaria with large gravel (3.2–6.3 cm), vertical and lateral movements of coho salmon (Oncorhynchus kisutch) alevins were more extensive and area utilized per alevin was greater than in small gravel (1.9–3.2 cm). At low density (50 per aquarium) the alevins moved farther towards the inlet, but the mean area occupied per alevin was the same as that at high density (100 per aquarium). Burial depths tested (20 and 30 cm) had no significant effect on vertical or lateral movements or on area utilized per alevin. Alevin orientation in the gravel, survival to emergence, and timing of emergence were not affected by any of the environmental variables examined.

ISSN:0706-652X    

DOI:10.1139/f70-141

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The use of a stainless steel kiln capable of careful environmental control permitted a comparison of the effects of 12 different Canadian woods on the flavor of smoked white-fish (Coregonus clupeaformis). A panel of 61 untrained judges, scoring on a 9-point hedonic scale, liked canned smoked whitefish better when it was smoked with red maple, red oak, trembling aspen, white ash, balsam, and birch. The flavors from beech and white oak were moderately well liked, whereas those from hard maple and hickory were of only borderline acceptability. Diamond willow and burr oak gave distinctly distasteful flavors. Comments from the untrained judges together with flavor descriptions from a panel of five trained judges classified distasteful flavors as medicinal, astringent, gasolinelike, and sour, depending on the wood source. Smoked products from female fish were liked slightly better than those from male fish.

ISSN:0706-652X    

DOI:10.1139/f70-142

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

WhenTilapia niloticawas acclimated to temperatures of 15–35 C and salinities of 0–30‰ in a vertical gradient tank, maximum temperature preferenda occurred at acclimation temperatures of 20 and 25 irrespective of salinity. Preferenda declined as acclimation temperature was increased above 25 C and, except at 0 and 7.5‰, declined as acclimation temperature was decreased below 20 C. The pattern of the relation between final temperature preferenda and salinity was similar to that reported between oxygen consumption for a given sustained swimming speed and salinity. The final preferendum was lowest at 15‰, close to the isosmotic salinity ofT.nilotica, and highest at the extremes, 0 and 30‰. Final temperature preferenda are in general agreement with optimum temperatures reported for growth, reproduction, and swimming performance.

ISSN:0706-652X    

DOI:10.1139/f70-143

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Habitat distributions of chinook and coho salmon underyearlings in the Big Qualicum River, Vancouver Island, B.C., under controlled flow conditions indicated that at similar sizes their habitat requirements during the first 3 months of stream life were similar. Just after emergence, fry of both species occupied marginal areas in association with bank cover. With increased size, the young fish moved into habitat of progressively higher velocity. However, differences between the species in time of emergence and size evidently resulted in a high degree of spatial segregation. Chinook fry emerged about a month earlier than coho, were larger upon emergence, and grew at a faster rate. Apparently, because of their larger size at a given time, chinook preferred higher velocity locations than coho.

ISSN:0706-652X    

DOI:10.1139/f70-144

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The objective of this study was to describe the organization of schools of the pelagic marine fishesScomber japonicus,Trachurus symmetricus,Engraulis mordax,Atherinopsis californiensis, andAtherinops affinis. Organization was studied in larval through adult stages by analysis of spatial and angular relations among fish in dorsal photographs of schools.In all species, schools of young fish, larval and juveniles, were typically less compact and showed greater differences in angular headings than did schools of adult fish. The rate at which school structure changed with size varied among species; it was rapid inScomberand the atherinids and slower inEngraulisandTrachurus. School organization differed among species at the adult stage. Schools ofScomberwere typically the most compact and organized;TrachurusandEngraulisschools were intermediate in their organization andAtherinopsschools were the least organized.Spatial and angular measurements were also used to develop inferences regarding the "following reaction" in four of the species. The similarity in angular headings between fish was used as the criterion of following. These analyses showed that the similarities in headings between two fish in a school decreased with the distance they were apart. The headings most alike between adjacent fish in a school were between those in file. These results suggested that the neighbor directly ahead of a given fish in a school is used more frequently as an angular reference for the following reaction than ones to the side.Analysis of the distances between neighbors in the four species indicated that fish were closer to adjacent neighbors in the file than they were to ones in rank. This suggested that spacing in the horizontal plane might be related to tail movement.

ISSN:0706-652X    

DOI:10.1139/f70-145

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Macrozooplankton distribution and abundance as well as limnological conditions were compared during 1949 and 1964 in Kootenay Lake, a large oligotrophic lake in southeastern British Columbia. The standing crop of macrozooplankton increased two- to threefold over 15 years. Changes in physical–chemical limnological conditions, such as a decrease in depth of light penetration, and increases inpH, specific conductivity, dissolved nutrients, and phosphates also occurred, indicating an increase in productivity.The most noticeable change in macrozooplankton was a shift in cladoceran species composition in the north arm of the lake, formerly dominated byDaphniabut now byDiaphanosoma. Size-selective predation, differences in food availability, and competition for food withDiaphanosomaandMysis relictaare suggested to be responsible for changes in the spatial distribution ofDaphniasince 1949.Examination of changes in midsummer zooplankton abundance between successive years (1964–66) indicated that total zooplankton was least abundant in 1964. Differences in abundance during this period were small when compared with those between 1949 and 1964.

ISSN:0706-652X    

DOI:10.1139/f70-146

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Data have been accumulated on seasonal levels of nutrients, primary production, and zooplankton. The occurrence and abundance of larval fish in the surface layers have been reported together with an approximate estimate of the standing stock of commercially exploited fish. The results indicate that beyond local effects, the Strait of Georgia is comparable in productivity to other nearshore waters at the same latitude. The total primary productivity of the waters was found to be approximately 120 g C/m2per year, but a high degree of areal patchiness in all production data emphasizes the necessity of basing predictions about particular subareas on knowledge specific to the subareas in question.

ISSN:0706-652X    

DOI:10.1139/f70-147

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Growth and reproductive patterns of the common lanternfishStenobrachius leucopsarus(Eigenmann and Eigenmann) are described by length-frequency analysis, otolith analysis, and examination of ovaries. Length-frequency analysis showed that growth is approximately linear, 1.59 mm standard length per month, during the 2nd, 3rd, and part of the 4th year of life. Yearling fish average 23 mm long, 2-year-olds 41 mm, and 3-year-olds 59 mm.Otolith analyses indicate that some fish may live to be 8 years old, but confidence in this method is limited to fish 5 years old or younger. Fitting mean lengths of age-groups defined by otolith analyses with the von Bertalanffy equation gave L∞ = 85 mm,k = 0.34. Back calculation of lengths at the times of formation of otolith annuli gave another set of estimated mean lengths of age-groups, which, fitted by the von Bertalanffy equation, describes a growth curve similar to the one described by otolith analyses. The inflection in growth in weight occurs at about 4 years of age.Time of spawning, determined from egg measurements, occurs from December to March. Reproductively mature individuals are 4 years old and older. Recruitment of young size groups is also seasonal, 20- to 25-mm individuals appearing in largest proportions in trawl samples in the winter, presumably about 8 months after spawning.Comparison with other studies indicates that spawning may occur earlier in Monterey Bay, California, than off Oregon, but growth rates and sizes of age-groups I–V are similar. Comparisons with published results of otolith analyses show similar age determinations for the smaller size groups.

ISSN:0706-652X    

DOI:10.1139/f70-148

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Three invertebrate species were subjected to acute (96-hr), followed by long-term (6-week) copper exposures under continuous-flow bioassay conditions. Survival, growth, reproduction, and feeding were the responses used for measuring toxicant effects. The average 96-hr median tolerance limits (TLm) values forCampeloma decisum,Physa integra, andGammarus pseudolimnaeuswere 1.7, 0.039, and 0.020 mg/liter total copper, respectively. The total copper concentration having no effect after 6 weeks exposure for all three species was between 8.0 and 14.8 μg/liter. The newly hatched amphipods obtained from the second 6-week study were exposed to copper for 9 additional weeks, and grew to the adult stage only in copper concentrations ≤ 4.6 μg/liter. After 5 weeks exposure to a water system, survival of newly hatchedGammaruswas markedly reduced when copper concentrations were between 12.9 and 6.2 μg/liter.

ISSN:0706-652X    

DOI:10.1139/f70-149

出版商:NRC Research Press    

年代:1970

数据来源: NRC