摘要:

Brook trout were exposed to photoperiods ranging from 4 to 20 hours per day and were held either at 8.5 °C or at 16°. The average diameter of the ova was used as an index of ovarian development while testicular maturation was determined from histological preparations.The gonadal cycles of both male and female trout were markedly affected by different photoperiodic regimes. The influence of long or short photoperiods depends upon the phase of gametogenesis in progress at the time and on the photoperiod in effect during earlier stages of the gonadal cycle. Evidence is presented which suggests that the maturation cycle of the gonads may be regulated by the normal seasonal changes of day length.An accelerated light regime can hasten the time of functional maturity in adult trout, but is without effect when applied to maturing fish in which gametogenesis is taking place for the first time. It is suggested that a stimulative effect of environmental factors is dependent upon maturation of the hypothalamic-hypophyseal mechanism.The rate of gonadal development is the same at 16° as it is at 8.5° provided the fish are exposed to natural day lengths. If fish are subjected to long or to short photoperiods, the gonadal response at 16° is quite different from that at 8.5°.

ISSN:0706-652X    

DOI:10.1139/f63-061

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Counts were made of the number of developing ova during the secondary growth phase of the oogenetic cycle in several groups of brook trout. An adjustment was made for the growth of the females since they increase appreciably in length during the secondary growth phase of the ova. Fecundity counts were then corrected to fish of a mean adjusted length. The results indicate that there is no major reduction in the number of developing ova during the secondary growth phase.

ISSN:0706-652X    

DOI:10.1139/f63-062

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The amounts, sectional distribution and some variations of fat, water-solubles, protein and water in cod fillets have been determined on denned, pre-rigor samples. It was found that the head-end of the fillet is the richest in protein. The middle section is the richest in water-solubles while the tail-end contains more fat and more water than any other part of the fillet. Only slight differences in the major components were detected between male and female specimens.

ISSN:0706-652X    

DOI:10.1139/f63-063

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The seaward migration of sockeye salmon smolts through the Babine Lake system to its outlet is examined by extensive tagging, direct observations and experimental orientation tests. The migration appears to be a well-oriented, non-random movement; it apparently commences from all lake regions at about the same time, suggesting a common triggering stimulus. When migrating, the smolts swim at a speed of 0.65 to 1.0 feet per second. The migration appears to take place primarily at near-surface depths; diurnally, most of the migration activity appears centered around the evening dusk period. There is a consistent increase in rate of travel as the season progresses; in large part this appears a result of increasing migration drive. Orientation tests with a view of only the sky show the smolts capable of time-compensated orientation in relation to celestial phenomena, and such tests at various points along the migration route show the preferred direction of smolts to correspond with the direction of most direct route to the outlet. Most smolts of the system show a constant preference for the northwesterly direction which would lead them rather directly to the outlet. However, one group which in the course of its migration to the outlet must make a 180° turn clockwise from southeast to northwest is found to have a corresponding shift in directional preference with time. Simple one-direction orientation, in one case shifting with time, is sufficient to account for ability to find the outlet. A positive relation is shown between rate of travel of tagged smolts and the hours of sunshine on days subsequent to their release.

ISSN:0706-652X    

DOI:10.1139/f63-064

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Oceanographic data collected in a line of stations extending seaward of the west coast of Vancouver Island, British Columbia, were reviewed and analyzed. On the basis of these data and the large-scale meteorological processes of wind, insolation, and precipitation, the characteristic structure of temperature and salinity in the coastal region was denned in five temporal stages throughout the year. These stages are presented as vertical sections along the line with characteristic ranges of values to be found in each of the structural elements.

ISSN:0706-652X    

DOI:10.1139/f63-065

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Fingerling steelhead trout were given individual performance tests in an experimental flume. Barriers confined the fish to a 10-foot (1 foot = 30.48 cm) testing section where they swam against a constant velocity of 2.5 feet per second. The end point of each test was reached when the fish was fatigued enough to allow itself to be impinged by the water flow on a net barrier. The study was designed to test what effect the application of Petersen disc tags had on swimming endurance, by comparing tagged, handled, and control groups.No permanent reduction of swimming endurance was experienced by the handled group (tag pin inserted, then removed). The tagged group experienced a permanent drop of about 50% in their swimming endurance due to the presence of the tag.

ISSN:0706-652X    

DOI:10.1139/f63-066

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Seasonal rise in shellfish toxicity in the Bay of Fundy in 1961 was coincident with increased abundance of a marine dinoflagellate,Gonyaulax tamarensis, and the appearance of toxin in plankton extracts. Experiments with unialgal cultures ofG.tamarensisisolated from the Bay of Fundy provided overwhelming evidence that it is the primary source of toxin in shellfish in this area and the Gulf of St. Lawrence.G.tamarensisis widely distributed in the North Atlantic and there is evidence of toxic and non-toxic strains of this species.

ISSN:0706-652X    

DOI:10.1139/f63-067

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

"Green" heavily salted split fish may be pre-cooled within a cold storage area with ice and salt, without imposing an excessive load upon storage refrigeration facilities and with little additional labour. Twelve pounds of ice plus 4 lb of salt per 100 lb of fish, uniformly applied between 3- to 4-inch thick layers of fish, will reduce the bulk fish temperature by 25°F (14 °C) in less than 8 hours.No mechanical equipment is required if flake ice be deemed a commodity. The direct cost may be estimated at less than 15 cents per 100 lb of finished (dried) fish.Pre-cooling is not essential under normal conditions but is recommended for heavily salted fish in which the degree of red bacterial contamination is unknown or suspected to be critical, and the storage refrigeration is not adequate to cool the product in a sufficiently short time.

ISSN:0706-652X    

DOI:10.1139/f63-068

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Movements of shiners through two-way traps on inlet and outlet streams of a small British Columbia lake were studied from 1956 to 1962. The date on which adults first entered the inlet each spring corresponded to the first rise of daily maximum stream temperature above 10 °C. Days on which increased numbers of shiners ascended the inlet were positively associated with days of rising daily maximum water temperature, and were not associated with water levels. Egg deposition occurred both in daylight and darkness. Downstream movement of shiner fry was greatest during periods of turbidity, and occurred largely during darkness. Shiners first spawned at age III or older; some lived to age V or VI. Number of adult shiners over 79 mm fork length was estimated by Petersen marking experiments to be about 13,000 in the 42-acre lake. A large interchange of adults took place in some years between the lake and parts of the watershed upstream; a small interchange occurred downstream. Many shiners entered a stream more than once each year. Many survived to spawn in two or more successive years. Movement into the streams varied markedly in different years and was small compared with the number of adults in the lake. Homing is suggested as a mechanism which determines the proportion of inlet-, outlet-, and lake-spawning in this species.

ISSN:0706-652X    

DOI:10.1139/f63-069

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Occurrences of seventeen species of zooplankton from near-surface oceanic and coastal waters about Britain have been correlated with temperatures and salinities, in temperature-salinity-plankton (T-S-P) diagrams, for the 12 months of 1957. Species exhibit distinctive relationships to the several water bodies, as these have been defined in temperature-salinity (T-S) diagrams. Similar relationships between species have been used as a basis to group species together and 6 such groups are discussed. The species of three of the groups are oceanic; one of these groups is restricted to warm water, but the others are less restricted. A fourth group consists of species confined to coastal waters. The remaining two occur in oceanic, mixed oceanic-coastal and coastal waters. The relationships to the water bodies are shown to persist throughout the seasonal fluctuations of properties in the waters.

ISSN:0706-652X    

DOI:10.1139/f63-070

出版商:NRC Research Press    

年代:1963

数据来源: NRC