摘要:

SUMMARYBrown trout of similar length and weight were fed a standard meal which contained a known number of food organisms of the same size‐group and taxon (seven taxa were used). The weight of digestible organic matter in a trout stomach decreased exponentially with time. i.e. at a constant relative rate. At a particular water temperature, the food organisms were either evacuated from the stomach at similar rates (Group 1: Gammarus pulex, Baetis rhodani, Chironomidae, Oligochaetes) or at progressively slower rates (Group 2:Protonemura meyeri, Hydropsychespp., Tenebrio molitor). Rates of gastric evacuation were not significantly different for food organisms of different size groups of the same taxon, or for different sized meals, or for different sizes of trout (range 20–30 cm), or for mixed and multiple meals (three meals over 16 h). Times are given for the gastric evacuation of 50%, 75%, 90% and 99% of the digestible organic matter in a meal. Starvation periods of 1, 2, 3,4 and 5 days prior to feeding did not affect evacuation rates. The rates were slightly, but not significantly, slower for starvation periods of 6 and 7 days, and were often significantly slower for starvation periods of 10, 15 and 20 days. Evacuation rates increased exponentially with increasing water temperature. It was possible to estimate both the rate and time for the gastric evacuation of different meals at water temperatures between 3–8°C and

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb01575.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYAn ecological study was made of the freshwater distribution of Actinomycete virus. One component of this, the virus ofActinoplanes, is highly specific and its pattern of occurrence mirrors that of its host. The occurrence of Streptomyces virus is more difficult to explain in ecological terms, but this is attempted. Micromonospora virus was not obtained and the significance of this is discussed. The Actinoplanes virus is characterized at the fine‐structure level by a polyhedral‐shaped head with a tail bearing a contractile sheath, the latter feature being previously undescribed for actinoph

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb01576.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe variability in the catch of perch traps set in Windermere over the period 1955–70 has been analysed. Altogether 2690 catches in four series have been treated by analyses of variance after a logarithmic transformation. A representative value of the between traps variance from all sources of variation has been used to estimate the reliability of the mean catches based on different numbers of traps. It is shown that many traps are needed to obtain consistent result

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb01577.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYMost Dutch lakes are small and shallow, resulting from peat dredging since the late 18th century. However, deep lakes have appeared recently owing to sand digging. Limnological features of one such lake, Wijde Biik (N. Holland), were studied during 1968–70. The lake with an average depth of 11 4 m (maximum depth 31 m) and area of 2·65 × 106m2is one of the deepest and biggest in the Loosdrecht‐lakes area. The lake is 125 cm below sea level, and underground water‐movements play an important part in the lake's hydrology.The lake exhibits thermal stratification on warm and calm days; since the lake surroundings are open and flat, wind and nocturnal cooling destroy such a stratification. There is continuous circulation from autumn through spring. The O2 saturation (%) in the upper water varies from 70 to 120%. Bottom waters were never anaerobic (lowest values 10% O2saturation).CI−(2·8m‐equiv.) and HCO−3(1·9 m‐equiv.) were the dominant anions just as Ca++(2·77 m‐equiv.) and Na+(2·5 m‐equiv.) formed the main cations. Chlorides have increased 2·5‐fold in the 40 years as a geochemical consequence of deepening. The surface drainage has minor influence on lake's water chemistry. Part‐P (10–140 μg/I) and PO4‐P (2–40 μg/1) recorded maximum and minimum respectively, and NO3‐N (0·05–1·15 mg/1) its minimum, during Microcystis abundance in August 1968. The SiO2‐Si decreased from February 1969 (400 μg/l) to June 1969 asDiatotna elongatumincreased. The Si‐decrease to<30% of the 1932 values is due to removal of Si‐rich clay and silt, due to sand digging.Chlorococcales were the important lake algae. Desmids were poor. Microcystis dominated as a rule from July‐September, achieving from 15 to 31 colonies/ml. Poor light transmission rather than nutrients limits plankton growth as also the primary production in the lake. Copepoda were the dominant zooplankton. Bosmina coregoni recorded between 2 and 44 individuaIs/1 in summer 1968 and was the main cladoceran. The average primary production during summers of 1969 and 1970 was 380 and 497 mg C m−2day−1respectively. Light limited production below 1 m—1 % light in 1969 and 10% in 1970 penetrated down to 4 m. About 70% of the production took place in the upper 2 m. Calculation of production according to theoretical models under‐estimated the observed values by 12% because Z0·5Iklay much above (0·8–2·8 m) the expected value of 3·5 m. It is suggested that in turbid lakes like Wijde Blikin situin

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb01578.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb01579.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThis paper presents information collected during a survey of stream‐dwelling triclads in two CO ntrasted areas of North Wales. The first study area was located in Caernarvon‐shire on the mainland of North Wales and included a mountainous region rising to over 1000 m with abundant cold springs. In contrast, the study area on the nearby island of Anglesey was characterized by relatively warm, slow‐flowing streams passing through gently undulating land which did not rise above 153 m. The object of the survey was to collect background data so that suitable streams could be chosen for more intensive studies on factors determining the distribution and abundance of stream‐dwelling triclads. Distribution maps for the commonly occurring species were prepared and observations on the relationship between stream source‐type and triclad fauna were obtained. The possible role of interspecific competition was of particular interest in this study and the results of this second phase of the work will be presented in a la

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb01580.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb01581.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe variability of the catch of pikeEsox luciusL. from gill nets in Windermere over the period 1961–71 has been analysed. Altogether 2952 catches have been treated by analysis of variance after an appropriate transformation. A representative value of the residual between catch variance has been used to estimate the reliability of the means of catches based on different numbers of net settings. It is shown that many settings of gill nets are required to get a reliable mean catc

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb01582.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Ghose, T. K. and Fiechter, A. (Eds) (1971).Advances in Biochemical Engineering I.Brinkhurst, R. O. and Jamieson, B. G. M. (1971).Aquatic Oligochaeta of the World.Macan, T. T. (1970).Biological Studies of the English Lakes.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb01583.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY