摘要:

In the laboratory 8 groups of Fulton River channel fry were starved for periods ranging from 1 to 7 weeks, then offered food ad libitum for 8 weeks. Fry withstood up to 4-weeks starvation with less than 10% mortality; beyond this point mortality increased sharply to 90% at 7-weeks starvation. At 5-weeks starvation both fry length and weight decreased significantly. Mortality continued when fish were offered food ad libitum after being starved. Among fish starved for 1 and 2 weeks, mortalities continued to be low, 0 and 6.6%, respectively; but, among fish starved from 3 to 5 weeks, mortalities rose considerably, ranging from 42 to 99%.

ISSN:0706-652X    

DOI:10.1139/f73-001

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Throughout the year, algae were the most frequently encountered organisms in the gut of larvae of landlocked and anadromous sea lamprey (Petromyzon marinus) and American brook lamprey (Lampetra lamottei). Relative abundance of organisms in the gut of both species was similar and did not change with length of larvae. In general, relative abundance of organisms in the gut was similar to that in samples of sediment and water. Occasionally, filamentous and episammic forms were not ingested because of their larger size.The number of algal cells ingested per unit weight of sea lamprey decreased inversely with size of larvae. In the summer the number of algal cells in the gut was about thrice that found in the winter for larvae of comparable size. Survival among diatoms evacuated from the digestive tract varied from 45% in July (17.8 C) to 90% in January (0 C). Representatives of theAchnantheshad the lowest survival rate (10–20%), while those ofAmphoraandCyclotellahad the highest (65–100%). Complete evacuation required approximately 54 and 70 hr at 16.0 and 2.5 C, respectively. Evacuation rate did not differ among the organisms consumed. The numbers of algae consumed by larval sea lamprey in a stream relative to their estimated abundance was considered negligible.

ISSN:0706-652X    

DOI:10.1139/f73-002

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The food of harp seals inhabiting the northwest Atlantic consists chiefly of pelagic fish, especially capelin,Mallotus villosus, and pelagic and benthic Crustacea (Euphausiacea, Mysidacea, Amphipoda, Decapoda), with smaller quantities of benthic fish. Feeding has been observed to take place on individual items by suction, and small fish are taken tail first. Feeding is intensive in winter and (by deduction) in summer, less intensive during spring and autumn migration, and in spring during whelping and moult. A weight loss in spring due chiefly to loss in thickness of subcutaneous fat (blubber) is most intensive in adult females as a result of lactation. This loss is made up slowly in summer. The preparturient females are partly segregated in midwinter on what may be the best feeding grounds. During lactation, and immediately following it when they are again segregated from other age-sex groups, adult females tend to feed on decapod Crustacea. In spring, the only time when all age classes are in the same geographic area, there is a stratification of feeding by size of organism and by depth, from chiefly Euphausiacea taken in surface waters by the weaned young, through capelin taken probably at intermediate depths by the immature animals, to herring, cod, and other groundfish taken by the moulting adults to depths of perhaps 150–200 m. Social feeding begins at about 1 year of age with the change from Crustacea to pelagic fish. From knowledge of the rate of feeding, body weights, and reproductive rates, the ecological efficiency of harp seals (i.e. weight of annual increment of population/weight of annual food eaten) is calculated at 0.005, a low figure. Annual weights of food items eaten by the northwest Atlantic population of harp seals are roughly estimated as: all organisms, 2 × 106metric tons; capelin, 0.5 × 106tons; and herring, 2 × 104tons. Predation by harp seals on capelin stocks off eastern Canada occurs only during the winter months when pack ice is present as a resting substrate, the same resource being consumed in the summer months by the great whales (Balaenopteridae).

ISSN:0706-652X    

DOI:10.1139/f73-003

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

In mature rainbow trout (Salmo gairdneri) receiving sublethal doses of endrin (4.3–145 × μg/kg body wt/day in 0.215–7.25 mg/kg of food) for 163 days and then forced to swim for 1 hr, the insecticide affected serum electrolytes, osmolality, total protein, cholesterol, cortisol, lactate, glucose, liver glycogen, and growth. Forced swimming alone altered 9 of 16 serum parameters examined. Apparent increases in serum Na and Cl and significant increases in osmolality and liver glycogen were directly related to dosage. A biphasic distribution of phosphate, total protein, and cholesterol with dosage was apparent. Glucose was increased about 50% by 145 μg/kg but was unaffected by lower doses. Variance analysis of zone electrophoretic patterns disclosed an in teraction between serum protein distribution and dose. Mobilization of liver glycogen was apparently inhibited by low doses and almost totally blocked by high doses. Correspondingly, trout given 14.5 μg/kg or more had lowered serum cortisol levels whereas the lowest dose elevated cortisol. Growth was inhibited appreciably by 145 μg/kg but not by lower doses. Visceral fat accumulated 4.8–8.7 μg endrin/g tissue in the 43 and 145 μg/kg exposures. We conclude that endrin caused dysfunction of physiologic processes critical to survival.

ISSN:0706-652X    

DOI:10.1139/f73-004

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Measurements were made of variations in water, protein, and soluble nitrogen in the hepatopancreas ofCarcinus maenasduring the intermolt cycle and in the ovary during ovogenesis. Analyses of hepatopancreas show three reasons for the variations in protein and soluble nitrogen contents: entry of water into the organism during and after exuviation and a corresponding dilution of the constituents, alternation of fasting and feeding during the intermolt cycle, and heavy demands of ovogenesis resulting in a decrease in nitrogen in the hepatopancreas. Variations in the metabolism of water and nitrogen are shown in the ovary during ovogenesis.

ISSN:0706-652X    

DOI:10.1139/f73-005

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The hexose monophosphates (glucose-6-phosphate (G6P), fructose-6-phosphate, and glucose-1-phosphate) accumulate postmortem in scallop adductor muscle (meats) during chill storage, increasing from only traces at death to levels totalling about 10 μmole/g after 8–10 days. In both unfrozen and thawed meats, G6P accounted consistently for 80–85% of the total hexose monophosphate, over a wide range of actual concentrations. Quick freezing at any time postmortem did not affect the concentrations of hexose monophosphates or related metabolic constituents. Thawing of the prerigor-frozen muscle, however, either slowly or rapidly, resulted in considerable G6P formation, and accelerated markedly the subsequent rate and extent of G6P production. The exceptionally high levels (− 20 μmole/g) reached in the thawed meats after 1–2 days at 5 C are implicated in the development of burned flavors, odors, and discolorations (i.e. Maillard browning reactions) observed in these thawed meats when cooked. While thawing of the prerigor-frozen muscle led to some hypoxanthine (Hx) and octopine formation, the subsequent rate of Hx accumulation at 5 C was three times faster in the thawed meats than in unfrozen meats. In meats frozen postrigor, thawing resulted in negligible change in concentrations of the metabolites; subsequent patterns of change during storage differed little from those in unfrozen muscle, although Hx accumulation was more rapid. Hx content showed potential as an index of quality in thawed scallop muscle.

ISSN:0706-652X    

DOI:10.1139/f73-006

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Wind-stresses for Hudson Bay for May and September were computed by the geostrophic relation and the balance equation, making use of data averaged over 30 years. The balanced wind-stress for either strong (September) or weak (May) pressure gradient situations was found to be substantially different from the corresponding geostrophic stress. The wind-generated circulations in the water in Hudson Bay calculated using the balanced and the geostrophic wind-stress showed significant differences, the former agreeing better with the observed average circulation.

ISSN:0706-652X    

DOI:10.1139/f73-007

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The effects of brine-freezing and plate-freezing at sea upon 2-thiobarbituric acid (TBA) values, concentration of long-chain free fatty acids (FFA), and flavor of Pacific halibut and chinook salmon were determined at intervals during subsequent storage of the glazed, polyethylene covered fish at − 30 C. Evaluations were conducted on both outside and inside muscle.Brine-frozen samples of outside muscle generally had higher TBA values than plate-frozen samples and the differences were most pronounced at intermediate storage times (26–45 weeks).Method of freezing significantly (P ≤ 0.05) affected the concentration of total FFA in Pacific halibut, and the total FFA concentration of both Pacific halibut and chinook salmon significantly increased with length of frozen storage. For both species the concentration of total FFA was significantly greater in outside than in inside muscle.Significant flavor differences between brine- and plate-frozen samples of outside muscle were evident at intermediate storage times for both species. For inside muscle of halibut, the significance of flavor differences generally increased with storage time whereas flavor differences for inside muscle of salmon were consistently nonsignificant.Taste panel results and TBA values indicated that, in comparison to plate-freezing, brine-freezing impaired the quality of outside muscle of Pacific halibut and chinook salmon during the early stages of frozen storage.

ISSN:0706-652X    

DOI:10.1139/f73-008

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The effects of brine-freezing and plate-freezing at sea on fleshpH, color (Huntera/bratio), thaw drip, and mineral concentration were determined at intervals during subsequent storage of the glazed, polyethylene covered fish at − 30 C.The difference in fleshpH between the brine- and plate-frozen samples was not significant for either halibut or salmon and thepH generally declined during storage.The changes in the Huntera/bratio of salmon were similar for both methods of freezing and the ratio generally increased slightly during storage.The thaw drip of halibut and salmon was less for the brine- than the plate-frozen samples after storage for 9–31 weeks whereas subsequently the brine-frozen samples had approximately equal or greater thaw drip than the plate-frozen. Except for plate-frozen halibut, thaw drip tended to increase with length of storage.Method of freezing did not significantly affect the potassium concentration of either halibut or salmon. For both species the sodium and chloride concentration of brine-frozen outside muscle was at least two to three times greater than brine-frozen inside or plate-frozen muscle.

ISSN:0706-652X    

DOI:10.1139/f73-009

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Changes in the concentration of long-chain free fatty acids were determined gas chromatographically from inside and outside muscle samples of brine- or plate-frozen Pacific halibut and chinook salmon stored for 9–81 weeks.With both species the concentration of individual free fatty acids was greater in outside muscle than in inside muscle. Few differences in concentration of free fatty acids were noted between plate- and brine-frozen samples. Numerous free fatty acids increased significantly in concentration during frozen storage. For both species the increase was most rapid during the first 26–45 weeks of storage. The detection of flavor differences was unrelated to the concentration of individual free fatty acids.

ISSN:0706-652X    

DOI:10.1139/f73-010

出版商:NRC Research Press    

年代:1973

数据来源: NRC