摘要:

Inferential techniques of numerical classification and principal coordinate analysis have been used to interpret data obtained on the Zn, Cd, and Cu concentration of 48 samples of oysters, comprising 473 individuals, grown at a variety of places around the Tasmanian coastline. A close association was obtained between proximity to heavily urbanized areas and concentration of metals found, oysters growing nearest urban areas having the highest concentrations of one or more of the metals. It appears that areas for commercial oyster growing should be sought in regions far from centers of urbanization and industrialization. Examination of samples of native oysters could be useful in providing an index or measure of environmental pollution.

ISSN:0706-652X    

DOI:10.1139/f74-138

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The rates of glycolysis and of breakdown of high-energy phosphorus compounds in prerigor muscle have been investigated at specific temperatures in the critical freezing range between −1 and −4 C to determine the temperature at which maximum degradation occurs. Glycolytic activity increased with decreasing temperature below −1 C, reaching a maximum rate with a broad peak between −2.5 and −3.2 C, then slowing down as the temperature dropped to −4 C. The maximum rate of breakdown of high-energy phosphorus compounds also occurred around −3 C. Loss of Δ7P was most rapid between −2.6 and −3 C with an average velocity of 3.5 μg atoms P/g per hour. From 25 to 41% of the initial Δ7P content was derived from creatine phosphate and this fraction was usually depleted within the first 2 h of frozen storage. Deamination of adenine nucleotides to inosine nucleotide compounds was faster at −3 C than at −2 or −4 C.

ISSN:0706-652X    

DOI:10.1139/f74-139

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

During slow warming of prerigor, quick-frozen scallop meats from −26 to −5 C, arginine phosphate and ATP were split rapidly between −8 and −6 C (in about 2 h), resulting in the accumulation of some ADP, and of large amounts of AMP, equivalent to 85% of the ATP originally present. Concomitant activation of glycolysis caused a substantial increase in fructose 1,6-diphosphate (FDP) concentrations, and smaller increases in the hexose monophosphates (HMP) and in octopine. The relatively low freezing point of prerigor scallop muscle, found to be −1.4 C, may be implicated in the stimulation of metabolic activity at a temperature as low as −5 C; the rates were faster than at 0 C and occurred at subfreezing temperatures considerably lower than those for most fish muscle.With continued storage at −5, FDP decreased as HMP concentrations rose sharply to maximum levels at 24 h; octopine accumulation was slower, attaining maximum concentrations at 5 wk. Rates of AMP degradation and of hypoxanthine accumulation were similar to those in unfrozen, iced scallop muscle, indicative of differential effects of temperature on the various metabolic enzymes.Because of the extensive metabolic activity in scallop muscle at temperatures near −5, the optimal quality of prerigor quick-frozen meats may be affected adversely by current commercial distribution and marketing practices where warming to temperatures just below the freezing point may be encountered.

ISSN:0706-652X    

DOI:10.1139/f74-140

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The viral disease lymphocystis was more common in age 0 bluegills (Lepomis macrochirus) in an area of Lake Monona heated by a power plant outfall than in unheated reference areas. Approximately 14,000 fish collected from July through October 1971 were examined. The infection became prevalent in mid-September and attained a maximum incidence in early October, when 11.6% of age 0 bluegills in the heated area had lesions in comparison with 5.5% in unheated areas in late September.Infected fish were longer than uninfected fish and usually exceeded 50 mm TL. Fish >50 mm long in the heated and in the unheated areas had similar lymphocystis incidence. Thus, higher lymphocystis incidence in heated than in unheated waters was largely explained by the greater percentage of bluegills longer than 50 mm TL in the outfall area.Leeches (Piscicolaria reducta) also were more prevalent in the heated area and may have increased lymphocystis incidence by creating foci for viral penetration or by acting as vectors.Slightly higher condition factors of infected than of uninfected bluegills were unexplained.

ISSN:0706-652X    

DOI:10.1139/f74-141

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

In late winter and early spring, benthic materials have been observed in patches (maximum size 400 m × 10 m) on the surface of thick fast ice. They parallel the shores of estuaries and are commonest in the southern Gulf of St. Lawrence. Materials in the patches are often in strikingly natural postures and include layers of bottom sediment and plants and animals (eelgrass, shellfish [infauna and epifauna] starfish, flounders, and sticklebacks). Apparently these are frozen to the lower surface of the ice in early winter at low tides, when ice comes in direct contact with them. When the tide rises, the ice floats and raises frozen-on materials with it. Thereafter, the floating ice is thickened by freezing of water to its lower surface, and the bottom materials are thus frozen in between two layers of ice. At the same time the ice above the frozen-in materials is thinned by ablation (sublimation and melting) at its upper surface. Eventually the benthic materials are exposed on the surface of the ice. Allied phenomena have been observed in the Bay of Fundy region. Antarctica is the only other place where this has been reported to occur regularly. These phenomena and conditions favoring their occurrence in the two areas are compared.

ISSN:0706-652X    

DOI:10.1139/f74-142

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

When rainbow trout (Salmo gairdneri) fry (underyearlings) were introduced into laboratory channels at three different prey levels and permitted to emigrate voluntarily, their density remained highest at the highest prey level. The distribution of fry was positively associated with a gradient in prey abundance. Both territory size and frequency of aggressive encounter varied inversely with prey level; the higher the prey level, the smaller the territory and the lower the frequency of aggressive encounter. Emigration from the channels was neither as rapid nor as marked when prey level was reduced, compared to when fry were initially introduced to different prey levels. However, frequency of aggressive encounter significantly increased when the prey level was decreased and significantly decreased when the prey was increased.

ISSN:0706-652X    

DOI:10.1139/f74-143

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Injection of a chinook salmon (Oncorhynchus tshawytscha) gonadotropin preparation into gonadectomized sockeye salmon (Oncorhynchus nerka) did not result in any increase in the plasma concentration of cortisol or cortisone, nor did it stimulate the activity of the interrenal tissue. On the other hand, injection of mammalian ACTH (Acthar) did result in an increase in the plasma concentration of cortisol and cortisone, and stimulated the interrenal tissue. The salmon gonadotropin preparation, however, elicited an increase in thyroid activity. The results suggest that in the salmon, ovulation is not caused by gonadotropin induced interrenal corticosteroidogenesis.

ISSN:0706-652X    

DOI:10.1139/f74-144

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Annual primary production rates of 270 and 170 g C m−2yr−1, respectively, were estimated for an inshore and offshore station in Lake Ontario using the in situ14C technique. A lag in increase of both biomass and photosynthesis rate at the offshore station in early summer was attributed to deep vertical mixing.Production/biomass quotients were computed using different biomass parameters such as particulate organic carbon, nitrogen, and chlorophylla. Carbon turnover rates of the seston on an areal basis (m2) were found to vary between 0.04–0.18 day−1and 0.01–0.21 day−1at the inshore and offshore station, respectively. Daily photosynthesis efficiency (energy fixed by photosynthesis/available energy) ranged from 0.1 to 1.8% at the two stations. Atypical photosynthesis–light intensity curves showed that algal populations behaved differently at different depths during the stratified period.

ISSN:0706-652X    

DOI:10.1139/f74-145

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f74-146

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Samples of blubber, muscle, liver, and kidney of short-finned pilot whaleGlobicephala macrorhynchaand long-snouted dolphinStenella(longirostris?) from waters adjacent to St. Lucia, Lesser Antilles, were analyzed for Hg, DDT, dieldrin, and PCB. Total Hg levels were high, ranging from 1.33 to 5.36 ppm in muscle (methylated fraction 42–100%), 2.28 to 14.00 ppm in kidney (methylated fraction about 14%), and 13.00 to 157.00 ppm in liver (methylated fraction 2–17%). ΣDDT in blubber ranged from 1.25 to 7.38 ppm, dieldrin in blubber from 0.007 to 0.04 ppm, and PCB in blubber from 0.69 to 5.00 ppm. The presence of the high Hg levels is attributed largely to natural sources, as the Lesser Antilles Island Arc is a site of intense cyclic tectonic activity. There may be some contribution from atmospheric sources. Both DDT and PCB could be largely the result of atmospheric transportation from higher Atantic latitudes, although local DDT spraying programs may have contributed. Certainly the circulation pattern in the Gulf of Mexico and Caribbean appears to rule out water-borne transport from the river systems of the Gulf States of the United States.

ISSN:0706-652X    

DOI:10.1139/f74-147

出版商:NRC Research Press    

年代:1974

数据来源: NRC