摘要:

A brook trout population in a stable stream environment was studied for 14 years. Population estimates were made each September, the catch of fish by anglers was recorded, and collections of fish were made to determine sex ratio, age at sexual maturity, and fecundity.The sex ratio was close to 1:1 for all age-groups. Some male trout were sexually mature at the end of the 1st year of life, most were mature at the end of the 2nd year, and all were mature at the end of the 3rd. No females were mature at the end of their 1st year, most were mature at the end of the 2nd, and all were mature at the end of the 3rd year of life. The regression of egg content on total length of female trout was determined.On the average 132,000 eggs were produced annually by the population in the study area, from which 4813 fish survived to the end of the 1st year; 1966 to the end of the 2nd; 356 to the 3rd; 29 to the 4th; and 0.6 to the end of the 5th year.The growth rate of the fish varied little during the period of study. Annual egg production varied between 80,000 and 212,000; the number of age-group 0 fish between 2809 and 6703; age-group I fish between 1589 and 2653; age-group II between 175 and 685; age-group III between 13 and 68; and age-group IV fish between 0 and 2.During the 14 years of observation, survival of adult fish tended to increase, leading to larger numbers of spawners. The larger egg complements which resulted tended to experience lower survival, thus largely preventing substantial increases in population size. Positive serial correlations exist in some of the series of estimates of numbers and of survival. No biological explanation is advanced for these serial correlations.Life tables and age-specific fecundity rates were calculated for 11 successive cohorts of brook trout. Net reproduction rates varied from 0.74 to 1.88, averaging 1.14. Thelxcomponents were about three times as variable as themxcomponents, indicating that changes in death rates rather than changes in birth rates have been the principal immediate cause of fluctuations in the population.Themxvalues were not related to population density in any way that would tend to regulate population size. Survival from the 12th to the 24th month of life was directly density-dependent. The pattern of survival from the 24th to the 36th month of life suggested an inverse density-dependent relationship.The number of 12-month-old progeny surviving varied from 2809 to 6703, and the parental egg complement varied from 80,000 to 212,000. The form of the relationship between these two variables could not be defined, partly because of the relatively small range of values of parental egg complement.Even though the form of the density-survival relationship was defined for several stages of the life history, no relationship between the size of a parental egg complement and the lifetime egg production of the progeny could be established, again partly because of the small range of values of the former variable.

ISSN:0706-652X    

DOI:10.1139/f67-121

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

A preliminary study was made of the freeze-drying of steaks 6–18 mm thick, at sample temperatures from 38 to 98 C and under total dryer pressures from 20 to 2000 μ, from pre- and postrigor, quick- and slow-frozen cod. The drying time varied directly with the thickness, inversely with the temperature of the sample, was not affected by total pressure within the dryer with the thinner samples, but appeared to vary inversely with pressure for those 12 mm thick. Total drying time was the same for 16-mm thick samples from pre- or postrigor, quick- or slow-frozen fish, but varied with 6-mm thick steaks.Evaluation of quality varied inversely with both thickness and temperature but was not affected by dryer pressure. Only the postrigor, slow-frozen samples were consistently below the quality level of consumer acceptance.

ISSN:0706-652X    

DOI:10.1139/f67-122

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Observations were made of salinity, temperature, and dissolved oxygen in 15 inlets in southeast Alaska in June 1964 and August 1965 with some observations in the southern inlets in May 1966. The data are summarized in tables, vertical profiles, and characteristic diagrams to provide a general description of the water property distributions in the larger inlets. Some comparisons are made with corresponding distributions in British Columbia inlets, previously described by Pickard in June 1961 in the Journal of the Fisheries Research Board of Canada.The larger Alaska inlets are longer and wider than those in British Columbia but the mean and maximum depths are similar. Sill depths are also similar and there are few very shallow sills. The river runoff into the Alaska inlets is generally less than into the British Columbia ones. The larger rivers (the minority) have a summer maximum from glacier and snowfield melt whereas the smaller ones generally have fall and winter maxima. Icebergs occur in some of the Alaska inlets; they are not found in any British Columbia inlets.Surface salinities were generally higher in Alaska than in British Columbia, and at the heads of the inlets the highest salinity values were in the "iceberg" inlets. Surface temperatures were between 5 C (in the iceberg inlets) and 18 C. Salinity increased with depth, reaching 90% of the deep water values by 20 m or less. The deepwater characteristics extended the British Columbia inlet values toward higher salinity (to 34‰) and lower temperature (to 2.5 C in the north). Dissolved oxygen decreased with depth in most cases with the lowest values of 1.5–2 ml/liter in the deep water where there was direct access for northeast Pacific Ocean waters. A conspicuous exception was that the deepwater oxygen values were high in the iceberg inlets (5–6.5 ml/liter). Secchi disc depths varied from 0.1 m near the large rivers to 11 m near the Pacific Ocean.There were some differences between the property distributions observed in 1964 and in 1965. Salinity and temperature differences in the surface layers are presumed to be due to seasonal variation in river runoff and net heat input. Lower temperatures in the deep water of some of the northern inlets in 1965 compared to 1964 may be due to larger than usual winter cooling between the years.

ISSN:0706-652X    

DOI:10.1139/f67-123

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The selected temperature for Atlantic salmon and rainbow trout, as determined in a horizontal gradient, increases with acclimation temperature over the acclimation range 5–20 C for salmon and 10–20 C for trout. The final preferendum for salmon is about 17 C. The results for rainbow trout suggest that the type of gradient used, i.e. vertical or horizontal, has a marked influence on the experimentally determined relation between acclimation temperature and selected temperature.

ISSN:0706-652X    

DOI:10.1139/f67-124

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Starvation-induced changes were observed in the selected temperature of some under-yearling salmonids. In Atlantic salmon an upwards shift occurred within 24–28 hr after cessation of feeding. In brook trout and rainbow trout a downwards shift occurred within 24 hr after cessation of feeding. Brook trout showed an initial overshoot. These changes were maintained more or less constantly throughout the starvation period which lasted from 15 to 22 days. In all cases the selected temperature had returned to its pre-starvation value within 24 hr after resumption of feeding.

ISSN:0706-652X    

DOI:10.1139/f67-125

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The isopropyl alcohol residues in fish protein concentrates prepared with this solvent can be determined by a hot extraction technique employing methyl acetate as the solvent and gas–liquid chromatographic analysis of the extract. Studies on vacuum stripping of fish protein concentrates and analysis of various samples suggest that the isopropyl alcohol is trapped mechanically inside particles because of formation of an impervious shell during drying.

ISSN:0706-652X    

DOI:10.1139/f67-126

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Fecundity of Atlantic cod from the Newfoundland and Labrador area was investigated in relation to fish length, weight, and age. Variations in fecundity were best explained in terms of size, either length or weight. The fecundity–length relationship was adequately described by the simple allometry formula; fecundity–weight by an arithmetic straight line. Differences in fecundity from north to south are described and discussed in relation to descriptions from other areas. Substantial differences in fecundity of western and eastern Atlantic cod are noted.

ISSN:0706-652X    

DOI:10.1139/f67-127

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

A hydrographic survey of the Penobscot River (Maine) estuary, made during 1963–65, showed that the lower estuary is subject to a high degree of stratification, extensive mixing occurs within intermediate strata in the middle reaches of the estuary, and near-uniform conditions prevail at the head of the estuary. This pattern generally prevails throughout the year, but it is subject to seasonal and tidal variations.Cold weather and high spring river discharge establish uniformly cold water temperatures, high dissolved oxygen, and low salinity conditions in the upper half of the study area. A pycnocline is readily identifiable and high dissolved oxygen prevails throughout the lower half of the estuary.Summer temperatures and low freshwater inflow accompanied by high turbidity and extensive pollution lead to partial stagnation and anoxic conditions in the upper estuary. Conditions improve slightly in the middle reaches and are favorable in the lower estuary, where marked vertical stratification exists for temperature, salinity, and density.Qualitative bottom samples indicated an absence of benthos in the upper estuary, limited numbers of species in the middle reaches, and an enriched fauna in the lower estuary. These findings are discussed with reference to bottom types and prevailing hydrographic data.

ISSN:0706-652X    

DOI:10.1139/f67-128

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

At 8–9 C, sockeye ova without added water maintained their initial fertility for 12 hr and a few were still fertile after 175 hr; sockeye milt maintained its initial fertility for 11 hr, and fertilized a few ova after 101 hr. Pink salmon ova maintained their initial fertility for 8 hr and some were still fertile at 129 hr; pink salmon milt maintained its initial fertility for 33 hr and fertilized 67% of the test ova at 57 hr, but none at 81 hr. Comparison of these results with those of tests at lower storage temperatures suggests that cooler storage would extend the period of high fertility.

ISSN:0706-652X    

DOI:10.1139/f67-129

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

An operating table and associated anesthetizing system for salmonids are described in detail. Techniques for vascular and urinary cannulation and sampling are also described along with comments on the use of physiological salines and anticoagulants. Utilization of these techniques and apparatus can make fish as convenient and useful an experimental animal as the laboratory rat.

ISSN:0706-652X    

DOI:10.1139/f67-130

出版商:NRC Research Press    

年代:1967

数据来源: NRC