摘要:

Cold-acclimated (6 °C) rainbow trout, exposed to lethal concentrations of cadmium, survived longer than warm-acclimated (12 and 18 °C) trout. Ten-day lethal thresholds indicated that cold-acclimated trout could also resist greater concentrations of cadmium. Calcium concentrations in the plasma of fish, exposed to 0.3 mg Cd/L, declined steadily during the period of exposure when subjected to five thermal regimes, different combinations of acclimation and experimental temperatures. The rate of decline in calcium concentrations was correlated with the rate of mortality. Survival times of 12°-acclimated trout subsequently exposed to cadmium at 6, 12, and 18 °C were inversely dependent on temperature, whereas survival times of trout acclimated to 6, 12, and 18 °C and subsequently exposed to cadmium at acclimation temperatures do not show the same temperature dependence. Survival times of 12 and 18°-acclimated and exposed fish were similar, indicating that temperature compensation may promote longer resistance of 18°-acclimated and exposed fish than when they are acclimated to 12 °C and abruptly transferred and exposed to cadmium at 18 °C. Symptoms of cadmium poisoning of the fish are consistent with the effects of extreme hypocalcemia and are similar to those reported in the literature for various fish. The decline of calcium concentrations in the plasma may be the direct cause of mortality.Key words: Cadmium, temperature, hypocalcemia, rainbow trout,Salmo gairdneri, toxicity

ISSN:0706-652X    

DOI:10.1139/f79-187

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

We present a bioeconomic model, of an intermediate degree of complexity and realism, of the prawn fishery of the Gulf of Carpentaria and adjacent waters in Northern Australia. The model employs 21 parameters to describe the performance of two classes of vessels exploiting several stocks of prawns. The model predicts the number of vessels of each class entering the fishery under free access, and the prediction is compared with available data. The model is also used to obtain estimates for the economically optimal number of vessels of each type.Key words: model, economics of fisheries, limited entry, prawn fishery, Australia

ISSN:0706-652X    

DOI:10.1139/f79-188

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A microgeographical population genetic study of the Japanese oyster,Crassostrea gigas, revealed a case of overdominance for a muscle protein (Mp-1) locus. This locus consists of a two allele polymorphism. A study of the relative "fitness" of the three genotypes (Mp-1105/105,Mp-1105/100, andMp-1100/100) revealed a heterozygote superiority in the segment of the oyster population at the lowest tidal level (+ 1.2 m). In segments of the population at higher tidal heights (i.e. + 1.8 and + 2.4 m), there appears to be a selective advantage forMp-1105allele since the highest "fitness" values belong to theMp-1105/105genotype. Since oysters do not appear at the field station lower than 1.2 tidal m, it could not be determined if theMp-1100allele had a selective advantage at tidal levels lower than 1.2 m. However, theMp-1105allele possibly exhibits a selective advantage in the subtropical marine environment of southern Japan, while theMp-1100allele is favored in the temperate marine environment of northern Japan. This suggests perhaps that a micro- and macrogeographical cline in gene frequency exists for theMp-1 locus due to a thermal gradient.Key words: Japanese oyster,Crassostrea gigas, population genetic study, overdominance, heterozygote superiority,Mp-1 locus, micro- and macrogeographical cline, thermal gradient, tidal height, latitude

ISSN:0706-652X    

DOI:10.1139/f79-189

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Laboratory experiments analyzing the correlation between epibiotic fouling and mortality of the eggs of the Dungeness crab,Cancer magisterDana, reveal that both can result from predation on crab eggs by the nemerteanCarcinonemertes erransWickham. Fouling appears to be stimulated by the release of yolk material into the egg clutch through worm feeding and defecation. Significant correlations exist between worm density and both fouling and mortality in field samples. The ranking of the correlations between these three parameters suggest that nemertean activity is the causative agent and that fouling is only incidentally correlated to egg mortality through its correlation to worm density.Key words:Carcinonemertes errans,Cancer magister, crab-egg fouling, crab-egg mortality

ISSN:0706-652X    

DOI:10.1139/f79-190

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Hourly series of summer phytoplankton biomass (ATP and chlorophylla) and photosynthetic capacity (14C assimilation and ATP increase in saturating light) were sampled in the lower St. Lawrence Estuary during the summer of 1977. Vertical stability of the water column was estimated by the Richardson number. From the results it is concluded that the mean level of biomass is an inverse function of critical depth, likely linked to the neap-spring tidal cycle (Mf). On the other hand, the fine fluctuations of biomass and photosynthetic activity were related to vertical stability, which varies according to the semi-diurnal tidal cycle (M2). A simple model was developed on the basis of Sverdrup's critical depth, combining theM2fluctuations in stability (degree of vertical mixing) toMfvariations in critical depth. Net biomass increases, observed in a nonturbid stabilized water column, cannot be explained by the growth rates computed from14C assimilation, but they are consistent with the measured rates of ATP production. Spectral analyses of time series of temperature and Richardson number suggest that low frequency water column stability variations amplify the spatial heterogeneity of a reacting parameter such as phytoplankton. On the other hand, a passive scalar such as temperature does not respond to these low frequency variations of stability. It follows that the study of stability spectra may give some insight into the low frequency control of phytoplankton dynamics.Key words: phytoplankton, St. Lawrence Estuary, variability, vertical stability, critical depth, Richardson number, Kendall's cross correlation, spectral analysis

ISSN:0706-652X    

DOI:10.1139/f79-191

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

An ecological model of Lake Ontario was used to assist in interpretation of data collected during the International Field Year for the Great Lakes (March 1972–April 1973). The analysis indicated that in spring and fall phytoplankton biomass is controlled by the interaction of incoming solar radiation and vertical mixing, in summer by silica- and phosphorus-limitation, and in late summer by zooplankton grazing. The influence of CaCO3precipitation on the light climate in late summer was also demonstrated. During the period of stratification, available phosphorus concentration is controlled by recycling within the epilimnion, primarily through plant and animal excretion. Comparison of simulated available phosphorus concentrations and concentrations of total dissolved phosphorus and soluble reactive phosphorus in the epilimnion suggest that the composition of the soluble unreactive phosphorus pool changes dramatically during the year and that the large pool of dissolved unavailable phosphorus during summer is composed of end products of material cycled several times through the food web.Key words: phytoplankton dynamics, phosphorus cycle, Lake Ontario, ecological model, nutrient recycling, phytoplankton production

ISSN:0706-652X    

DOI:10.1139/f79-192

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Juvenile Rogue River spring Chinook salmon (Oncorhynchus tshawytscha) reared at two temperatures and photoperiods for a 2-yr period were examined for cyclic changes in gill (Na + K)–ATPase specific activity. Three peaks in activity were observed: a peak in October of the first year, a second higher peak the following May, and a peak in October of the second year. Exposure to photoperiods artificially advanced 3 mo (July–October) suppressed the October peak during the first year, but did not greatly alter the subsequent two peaks in activity. The temperature at which the fish were reared did not directly affect the changes in enzyme activity. However, growth rates varied in response to water temperature. Altered growth rates resulted in differences in the cyclic changes in gill (Na + K)-activated ATPase activity in the two temperature groups. A threshold of 8 cm was suggested as the minimal size at which the fish could respond to the appropriate photoperiod by altering the gill (Na + K)–ATPase activity.Key words: (Na + K)–ATPase, chinook salmon, temperature, photoperiod,Oncorhynchus tshawytscha.

ISSN:0706-652X    

DOI:10.1139/f79-193

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Three different characterizations of limnetic zooplankton communities from lakes of the Bruce Peninsula, Ontario are compared with respect to their usefulness in limnological studies: a conventional taxonomic one, one based on the body size and feeding ecology of the organisms, and one based on image analysis of the particle size spectrum. In comparison with the taxonomic characterization, the ecological and image analysis characterizations reflect zooplankton community features which are more closely related to the efficiency and nature of energy flow through pelagic ecosystems. Furthermore, it is demonstrated that these features have stronger statistical relations to morphometric and hydrological properties of lakes. The ecological and image analyses are thus not only more useful in studies seeking to make predictions about lake function from lake type but actually require less time, money and expertise in the acquisition of zooplankton data. In comparisons of zooplankton communities from the disparate faunal regions of the Bruce Peninsula, Ontario and southeast Asia, particularly Sri Lanka, more useful functional insights emerge from a body size-feeding ecology characterization than from a taxonomically based one.Key words: community structure, image analysis, Bruce Peninsula, tropical zooplankton, zoogeography, multivariate analysis

ISSN:0706-652X    

DOI:10.1139/f79-194

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Five freshwater algae (Chlamydomonas reinhardi,Scenedesmus quadricauda,Anabaena variabilis,Pseudoanabaena catenata, andCryptomonas erosa) were grown in batch culture without nutrient limitation and with various degrees of P and N limitation. They were analysed for several aspects of composition and some metabolic activities of potential use as indicators of nutrient deficiency to aid in establishing values indicative of the presence or absence of nutrient deficiency. Ratios of N/C, P/C, N/P, protein/C, carbohydrate/C, and protein/carbohydrate most clearly differentiated between no, P, and N deficiency. The initial saturated rate of phosphate uptake, P debt, and alkaline phosphatase activity increased distinctly in P deficiency in some of the algae but not in others. Similarly, the initial saturated rate of ammonium uptake and N debt rose in some but not all N-deficient algae.Cryptomonas erosatended to form walled resting cells (cysts) during growth into P or N deficiency.Key words: algae, nitrogen, nutrient deficiency, nutrient uptake, phosphatase, phosphorus

ISSN:0706-652X    

DOI:10.1139/f79-195

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Incidence and effects of bacterial kidney disease (BKD) were determined in wild, naturally reproducing populations of brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Salmo gairdneri) in a small lake and stream system in southeastern Wyoming, USA where BKD epizootics have been observed since 1972. During 1976, dead fish were collected at three upstream stations, and 60 live fish were collected from each of 11 stations. All fish were necropsied, and virological, bacteriological, and parasitological examinations were conducted by standard methods. An indirect fluorescent antibody technique was used to detect the BKD organism in cultures and kidney tissue smears. Bacterial kidney disease was diagnosed in 100% of the dead brook trout collected. Incidence among live fish ranged from 83% at an upstream station to only 3% at the most downstream location, and was highest in brook trout and lowest in rainbow trout. Two longnose suckers (Catostomus catostomus), the only non-salmonids collected, were found negative for BKD. Clinical signs of infection and the most severe infections were found only in brook trout. Five age-classes of feral brook trout were involved in the epizootics. Since other known pathogens were essentially absent, it is believed that all deaths were due to BKD. Relationships between species susceptibility to BKD, age-classes, water chemistry and water temperatures, and certain ecological conditions are discussed.Key words: bacterial kidney disease, feral trout, epizootics, brook trout, brown trout, rainbow trout

ISSN:0706-652X    

DOI:10.1139/f79-196

出版商:NRC Research Press    

年代:1979

数据来源: NRC