摘要:

The conclusions of Ricker (1958) are confirmed in series of 200 generations in which environment effects are simulated. The best constant rate of exploitation is very close to the maximum equilibrium rate when there is no environmental variation. A higher catch is obtained when an optimum portion of the stock is reserved for escapement and the remainder is harvested up to the level of the maximum equilibrium rate. Still higher catches are associated with reserving an optimum portion of the catch for escapement and harvesting all of the remainder. In general, these kinds of benefits are greatest at higher levels of environmental variability.

ISSN:0706-652X    

DOI:10.1139/f64-001

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

The relationship between rate of development of eastern Pacific cod eggs and water temperature was found to be linear at temperatures of 5–11 °C. Time to 50% hatching ranged from 8.5 days at 11 °C to 17 days at 5 °C. Most successful hatching occurred at the lowest temperature. Newly hatched larvae from 5° water had an average length of 4.45 mm.

ISSN:0706-652X    

DOI:10.1139/f64-002

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

The toxicity of copper and zinc sulphates to immature Atlantic salmon (Salmo salarL.) was tested in soft water.The relation between concentration of metal and survival-time could be fitted by a straight line when logarithms were used. A sharp break in this relation marked theincipient lethal level, where survival became indefinitely long. Incipient lethal levels were 48 μg/l of copper and 600 μg/l of zinc.In solutions containing both copper and zinc, fish died twice as fast as would occur if the 2 metals were simply additive in their lethal action. Resistance-times in zinc solutions were increased at pH 7.9–9.3, and results fitted the hypothesis that dissolved zinc was toxic, but not suspended zinc. Survival in a given concentration of zinc was 4 times as long at 5° as at 15 °C, and the incipient lethal level was at least 1.5 times higher, with fish acclimated to each temperature.

ISSN:0706-652X    

DOI:10.1139/f64-003

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

The locations of tagged parr and fin-clipped fry were observed from summer through early winter in a 1000-ft (328-m) study area of a small coastal stream. Tagged parr were usually found in or near places of original capture which are herein designated as homes. Parr whose homes were in pools, which appeared to be as suitable habitats as riffles, and those in adjacent riffles appeared to stay in their respective habitats. Some returned to their homes after having been moved as much as 700 ft (213 m) upriver or downriver. Fry were most numerous in shallow riffles and appeared to remain within small areas of the stream during summer but moved into parr habitats, the pools and deep riffles in autumn.

ISSN:0706-652X    

DOI:10.1139/f64-004

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Irradiation of refrigerated brines with ultraviolet radiation was effective in controlling bacterial development in the brine during the post-mortem storage of lingcod (Ophiodon elongatus) and sockeye salmon (Oncorhynchus nerka). The bacteriological and organoleptic quality of the fish was not improved by continuous or intermittent exposure of brines to ultraviolet radiation. Irradiation of highly contaminated turbid brines resulted in the killing of a large percentage of the initial bacterial population. Intermittent or continuous irradiation of brines produced off-odours in the brine and in the stored fish. Discolouration developed in the irradiated brine and on exposed surfaces of the stored fish.

ISSN:0706-652X    

DOI:10.1139/f64-005

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

During the 1955 cruise of HMCSLabradorto the Canadian Arctic an unusual mass of cold saline water was discovered in Foxe Basin and Channel. Temperatures as low as −1.90 °C were observed in association with salinities of the order of 33.75 and 34.00‰.An explanation of the origin of this water is presented and compared with additional studies conducted by the author in the same area in 1956.

ISSN:0706-652X    

DOI:10.1139/f64-006

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Growth rates of Atlantic cod vary both between populations in the same year and within a population over a series of years. The latter type of change is selected for detailed study, using an example found in the population resident in the western Gulf of St. Lawrence (ICNAF Division 4T). A real change in growth is verified by examining ageing methods, selectivity of sampling, tagging returns, and by measuring increments on the otoliths. Laboratory experiments showed that, when food supply is unlimited, food consumption increases with increasing temperature, and that growth increases with increasing food consumption. Direct correlation between temperature and growth changes is not established.Cod growth changes in Division 4T are found to be the result of changes in abundance and availability of herring as food, plus changes in competition for food resulting from density changes in fish-eating members of the cod population.

ISSN:0706-652X    

DOI:10.1139/f64-007

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Tripolyphosphate dipped and undipped control paired cod fillets stored at −12 °C showed no differences occurring on storage in extractable protein, lipid hydrolysis, or thaw drip. A higher yield of frozen and of thawed fillets was obtained from the dipped samples due to water uptake.No specific effect of tripolyphosphate on thaw drip was obtained at the ionic concentrations used, but it is postulated that such effects might occur in the presence of about 1% salt.

ISSN:0706-652X    

DOI:10.1139/f64-008

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Analysis of fish brain for the dipeptide homocarnosine has led to the discovery of a new oligopeptide which is named neurosine. This substance contains γ-aminobutyric acid (GABA) and histidine residues. Most of the histidine present in a water soluble fraction from fish brain appears to be in the form of a tetrapeptide consisting of glycine, glutamic acid, GABA and histidine. Neurosine is ninhydrin negative, heat stable, and has a high Rfvalue when chromatographed in a butanol–acetic acid–water solvent system. The evidence at present suggests that this compound may be a cyclopeptide or contains a pyrrolidone or diketopiperazine ring structure.Neurosine is present in high concentration in the brain of the killifish,Fundulus heteroclitus, approximately 0.1–1.0 μg of peptide per milligram of tissue. It also has been found in other bony fish, amphibians and reptiles but is absent in cyclostomes, elasmobranchs, birds and mammals. Neurosine is not present in any tissue but brain.

ISSN:0706-652X    

DOI:10.1139/f64-009

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Thawing time for frozen blocks of dressed cod (Gadus morhua) was investigated. Observations were made on the effect of size of individual fish, water recirculation rates, water temperature, block height, thickness and orientation, separation of individuals from the block at some intermediate time, and the use of sodium alginate to promote quicker thawing. Over the range investigated, the first two variables did not affect thawing rate; the remainder were of importance. Blocks 4 andinches (102 and 115 mm) thick, weighing 75–80 lb (34–37 kg), were separated and thawed in 60°F (15.5 °C) water in about 3 and, respectively. These times were equal to or better than the times for freezing between plates under best local commercial conditions. In comparison, similar blocks can be thawed in aboutin a commercially available dielectric thawer. Thawing blocks of dressed fish in recirculated water thus merits consideration with other methods.

ISSN:0706-652X    

DOI:10.1139/f64-010

出版商:NRC Research Press    

年代:1964

数据来源: NRC