摘要:

High variation in yearly samples of insecticide residues found in landlocked salmon from Sebago Lake, Maine, has necessitated an evaluation of sampling methods and an investigation of causes of variation. A sample of 59 male salmon, composed of ages III+, IV+, and V+, and representing fish in poor and good body condition was collected from a spawning run in the fall of 1967 and analyzed for DDT, DDD, DDE, dieldrin, and fat content. Levels of insecticide residues were found to be highly dependent on age and fat content. DDD and DDE increased with age and fat content, and dieldrin increased with fat content. Age and fat content were interdependent in their effects on DDT levels. DDT was significantly higher in high-fat than in low-fat fish at ages III+ and IV+ but not at age V+, showing a decrease with age among fish with high fat content and remaining constant with age among fish with low fat content. It is recommended that completely random selection of fish for insecticide analyses be abandoned in favor of stratification by sex, age, and fatness. Some of the possible causes of variation in insecticide content of salmon are discussed.

ISSN:0706-652X    

DOI:10.1139/f70-001

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The filtration and ingestion rates ofDiaptomus oregonensisfemales and stage V copepodids were examined in three experimental situations. When unialgal cultures of 20,000 cells per milliliter were offered toD.oregonensisthe filtration rates remained constant for cells ranging from 120 to 10,000 µ3. When a mixture of diatoms was offered the animals did not filter cells ranging from 1 to 60 µ3despite the fact that the cells in this size range were concentrated at about 20,000 per milliliter. When natural phytoplankton from Marion Lake was used as a food source, the filtration rates were low for cells smaller than 100 µ3, increased to a maximum of 12.9 ml per animal per day for cells ranging from 102 to 333 µ3, and remained constant with increased cell volume and decreased cell concentration. Several species ofCyclotellaandMerismopediawere not removed from the Marion Lake plankton byD.oregonensis.

ISSN:0706-652X    

DOI:10.1139/f70-002

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Yellow phosphorus is extremely toxic to aquatic life. In herring, salmon, and lobster, the toxic effect of phosphorus is irreversible and probably cumulative. For herringLT50(hours) = 300/C0.87, where C = μg/liter of phosphorus. No clear indications of an incipient lethal level were found, anLT50being obtained even at a concentration of 2.5 μg/liter. Incipient lethal levels of yellow phosphorus for lobster, salmon, and beach flea are 40 μg/liter, 18 μg/liter, and 3–4 mg/liter, respectively. Poisoned fish turn red and show signs of extensive hemolysis. Blood of lobster congeals, and after death the thorax may be filled with thick gel and the heart grossly distended. For lobster,LT50(hours) = 300–0.17x, wherex= product of phosphorus concentration and exposure time (μg days/liter). The oxidation of dispersions of yellow phosphorus in water is kinetically a first-order reaction with half-life of 2–7.5 hr. The adsorption of yellow phosphorus on a solid support such as bottom mud substantially decreases the rate of oxidation.

ISSN:0706-652X    

DOI:10.1139/f70-003

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Expressible fluid was obtained from fillets on the 1st, 4th, and 14th days of refrigeration. The protein concentration was determined and electrophoresis using cellulose polyacetate strips was performed on each sample. The protein concentration remained constant between 6 and 8 g/100 ml over the 2-week period. Qualitative and quantitative examination of the densitometry tracings revealed that protein(s) having specific migratory characteristics were strongly associated with the duration of storage at 2 C.

ISSN:0706-652X    

DOI:10.1139/f70-004

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A method was developed for selecting hybrid trout for deep-swimming ability, for use in a breeding program to combine in one strain the early-maturing character of brook trout (Salvelinus fontinalis) with the deep-swimming ability of lake trout (S.namaycush). The method involves testing hybrids in pressure tanks and selecting individuals that, like lake trout, retain most of their swimbladder gas during the test period. For a sample of F2hybrids the range of pressures at which the fish floated when anaesthetized was almost entirely between the medians for samples of the two parent species. Successive tests of marked individuals showed good repeatability of flotation measurements. The method is concluded to be reliable for large-scale selection of fish with ability to retain swimbladder gas.

ISSN:0706-652X    

DOI:10.1139/f70-005

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The concentration of zinc in oysters was highly variable — samples from relatively unpolluted estuaries of North Carolina contained, on the average, 85–245 ppm zinc, based on wet weight. Internal tissues, like adductor muscle and pericardial sac, had zinc levels less than half those of external tissues but zinc was nonetheless distributed uniformly throughout the animal tissues. During 1964–66, North Carolina oysters contained 2–20 pCi65Zn from fallout per 100 g wet weight. Specific activity of65Zn in these oysters during 1965–66 was in the range 90–300 pCi/g Zn, and was declining with an apparent half-life of 276 days.

ISSN:0706-652X    

DOI:10.1139/f70-006

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Nearly all the zinc in oysters is bound, either to soluble high-molecular weight proteins or to structural cellular components such as cell membranes. Oyster alkaline phosphatase is a zinc metalloenzyme, as indicated by in vitro inhibition studies with various metal-binding agents. Dialysis of soluble tissue extracts atpH 7–9 removes up to 96% of the total zinc without effect on alkaline phosphatase. If alkaline phosphatase is considered representative of the metabolic functions of zinc in oysters, most of the zinc accumulated by oysters must be superfluous to the animal's requirements.

ISSN:0706-652X    

DOI:10.1139/f70-007

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The in situ productivity of both the phytoplankton and the macrophytes in Marion Lake, B.C., was determined from April 1966 through September 1966, by using14C techniques. The uptake of NaH14CO3was measured in selected macrophytes by enclosing them in Plexiglas chambers. These plants were then combusted in oxygen, and the14CO2was absorbed in toluene-POPOP-ethanolamine. Radioassay was accomplished by liquid scintillation. In addition to the14C method, an organic weight method was used to measure macrophytic productivity.The productivity of the macrophytes was always higher than that of the phytoplankton. There was a considerable difference in the estimates of the macrophyte productivity arrived at by the two different methods, and reasons for this are discussed.The total productivity of the lake is very low when compared with lakes of similar latitudes because of low phytoplankton productivity. It is concluded that in Marion Lake the macrophytes are more important primary producers than the phytoplankton.The difficulty of comparing data between this and other studies is discussed, and the need for standardization of methods is emphasized.

ISSN:0706-652X    

DOI:10.1139/f70-008

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

In scallop adductor muscle stored at 0 C, postmortem degradation of adenosine triphosphate (ATP), the predominant nucleotide at death, primarily follows the route ATP → adenosine diphosphate (ADP) → adenosine monophosphate (AMP) → adenosine → inosine → hypoxanthine (Hx). In one lot of scallops, however, inosine monophosphate (IMP) was present as an intermediate along with AMP. Hence, an alternate pathway, similar to that in fish muscle, whereby AMP is degraded to inosine and Hx via IMP rather than adenosine, may exist under certain (undefined) conditions. ATP dephosphorylation was much slower than in fish muscle; however, a rapid turnover of the intermediates in the degradative sequence, indicating relatively high activities of the enzymes catalyzing these reactions, resulted in the formation of appreciable amounts of Hx (3–4 μmole/g) within the edible storage period. In preliminary tests, taste scores correlated well with Hx contents, suggesting that measurement of Hx content may be a useful index of quality in scallop meats.Column chromatographic analyses showed that adenine nucleotides and their degradation products accounted for about 90% of the total acid-soluble purines and pyrimidines in scallop adductor muscle, with nicotinamide adenine dinucleotide and uridine diphosphate glucose as the principal minor nucleotide constituents. The muscle also contained considerable amounts of homarine (2–3 μmole/g). Glycolysis showed no relation to nucleotide degradation, both processes demonstrating a relatively slow postmortem catabolic rate in scallop muscle.

ISSN:0706-652X    

DOI:10.1139/f70-009

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Of the life-history stages of the Dungeness crab,Cancer magister, the early larvae are more sensitive to Sevin than are juveniles and adults. A concentration of 1.0 mg/liter did not affect egg hatching but prevented molting of all prezoeae to zoeae. The concentration that killed 50% of the first stage zoeae during a 96-hr exposure (96-hr EC50for death) was estimated to be 0.01 mg/liter. Few zoeae were killed in 24 hr by 82.0 mg/liter, but the 24-hr EC50for death within 15 days after the exposure was estimated to be 0.015 mg/liter. The 24-hr EC50for cessation of swimming, which was not always permanent, was 0.0065 mg/liter. Survival of zoeae after 25 days exposure to concentrations of 0.0001, 0.00032, 0.001, 0.0032, and 0.01 mg/liter were 83, 60, 69, 21, and 0%, respectively, and control survival was 79%. Molting was delayed at a concentration as low as 0.0001 mg/liter.Young juvenile crabs are more sensitive to Sevin than are older juveniles or adults. The 24-hr EC50's for death or irreversible paralysis were estimated to be 0.076 and 0.35 to 0.62 mg/liter for second and ninth stage juveniles, respectively. The behavior, growth, and survival of juvenile crabs were not affected when the animals were exposed to 0.032 mg/liter of Sevin for 24 hr and then held in clean sea water for 44 days. The 24-hr and 96-hr EC50's for death or irreversible paralysis were 0.49 and 0.26 mg/liter, respectively, for adult crabs. After eating cockle clams that had just been exposed for 24 hr to 1.0, 3.2, and 10.0 mg/liter of Sevin, 22, 77, and 100% of adult crabs, respectively, were irreversibly paralyzed within 6 hr. The significance of these findings in field application of Sevin to control oyster pests and predators is discussed.

ISSN:0706-652X    

DOI:10.1139/f70-010

出版商:NRC Research Press    

年代:1970

数据来源: NRC