EFFECTS OF DIETARY LEVELS OFCARBOHYDRATE,LIPID,PHOSPHORUS ANDZINC ON THE GROWTH,FEED CONVERSIONAND PROTEIN EFFICIENCY RATIO OF NILETILAPIA (OREOCHROMIS NILOTICUS)

INTRODUCTION The eonversion of dietary Protein,liPid and earbohydrate in the body of thevertebrate 15 conneeted with the intermediate metabolism Proeesses in whieh themetalloenzymes Play very imPortant roles.Anderson et al.(1984)and Teshimaand Kanazawa(1 986)Proved the maintenanee of ProPer Protein and liPidlevelsin the diets eoneomitant with inereasing the dietary earbohydrate eontent to 40%ean Promote teh growth of Nile tilaPia fingerlings.EI一Sayed and Garling(1988)indi eated th…     

DIETARY PHOSPHORUS REQUIREMENT OF YOUNG ABALONE, HALIOTIS DISCUS HANNAI INO.

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COMPARATIVE STUDIES ON THE FEEDING CAPACITY OF SILVER CARP AND BIGHEAD CARP

Study of the feeding capacity of silver carp and bighead carp by means of experimental ecologyshowed that the filtering frequency of silver carp was slightly greater than that of bighead carp,but thatthe latter's suction volume was much greater than the former's so the filtering rate(filtering frequency mul-tiplied by the suction volume)of silver carp was smaller than that of bighead carp.The filtering efficien-cy of silver carp for phytoplankton was greater than that of bighead carp for them.The removal ratesof silver carp for phytoplankton were greater than those of bighead carp,but for zooplankton the formerwere smaller than the latter.For food particles about 70 μm both removal rates were almost equal.The feeding habits of the two species in natural waters is also discussed in the paper.     

A TAXONOMICAL AND ECOLOGICAL SURVEY OF ROTIFER COMMUNITIES IU KROTTENSEE (AUSTRIA)

The composition and distribution of benthic, periphytic and planktonic rotifers in different habitatsin Krottensee were investigated. Sixty-five rotifer taxa were identified, their relative abundance estimated. Classification of the data set by cluster analysis allowed the recognition of distinct habitat groupe con-fined to acid bog ponds, macrophytes, sediments, and open water. Five groups of rotifer taxa were identifiedon the basis of their habitat preferences and the occurrence of the taxa. Highest diversities were found onmacrophytes and in acid bog ponds.     

墨吉对虾体长与体重关系的计算及其在生产中的应用

本文研究墨吉对虾(Penaeus merguiensis)体长(L)与体重(W)的关系,经回归分析得其关系式。根据此关系式计算得体长和体重换算表,对指导生产具有现实意义。     

Sources and distribution of trace elements in Estonian peat

This paper presents the results of the distribution of trace elements in Estonian mires. Sixty four mires, representative of the different landscape units, were analyzed for the content of 16 trace elements (Cr, Mn, Ni, Cu, Zn, and Pb using AAS; Cd by GF-AAS; Hg by the cold vapour method; and V, Co, As, Sr, Mo, Th, and U by XRF) as well as other peat characteristics (peat type, degree of humification, pH and ash content). The results of the research show that concentrations of trace elements in peat are generally low: V 3.8 ± 0.6, Cr 3.1 ± 0.2, Mn 35.1 ± 2.7, Co 0.50 ± 0.05, Ni 3.7 ± 0.2, Cu 4.4 ± 0.3, Zn 10.0 ± 0.7, As 2.4 ± 0.3, Sr 21.9 ± 0.9, Mo 1.2 ± 0.2, Cd 0.12 ± 0.01, Hg 0.05 ± 0.01, Pb 3.3 ± 0.2, Th 0.47 ± 0.05, U 1.3 ± 0.2 μg g^− 1 and S 0.25 ± 0.02%. Statistical analyses on these large database showed that Co has the highest positive correlations with many elements and ash content. As, Ni, Mo, ash content and pH are also significantly correlated. The lowest abundance of most trace elements was recorded in mires fed only by precipitation (ombrotrophic), and the highest in mires fed by groundwater and springs (minerotrophic), which are situated in the flood plains of river valleys. Concentrations usually differ between the superficial, middle and bottom peat layers, but the significance decreases depending on the type of mire in the following order: transitional mires – raised bogs – fens. Differences among mire types are highest for the superficial but not significant for the basal peat layers.The use of peat with high concentrations of trace elements in agriculture, horticulture, as fuel, for water purification etc., may pose a risk for humans: via the food chain, through inhalation, drinking water etc.     

Factors affecting the elimination of PCBs in the marine copepod Acartia tonsa

The effects of feeding, egg laying, and fecal pellet production on the elimination of polychlorinated biphenyls (PCBs) from the marine copepod Acartia tonsa were studied in a series of experiments. Copepods were exposed to ¹⁴C-labelled Aroclor 1254 and allowed to depurate in clean seawater. Copepods fed during depuration eliminated PCBs more rapidly than unfed copepods whether or not the original PCB exposure medium had contained food. Both eggs and fecal pellets contained PCBs during depuration, with the weight specific concentration of PCB in the eggs (up to 407 ppm, dry weight) exceeding four times that in the females that produced them. Female copepods eliminated PCBs twice as rapidly as males, indicating that egg production is an important route for PCB elimination.     

Mental Mapping: A Lesson That Creates Itself

Abstract

Mental image and place-preference maps of college students in Florida were created through a two-part lesson. The patterns revealed by these maps were linked to students' life experiences, census data on migration and income, and similar studies conducted in other states. Students prefer states with established migration links to Florida and better income/job opportunities. Because the maps could not be created without their input, students were wholly engaged in a lesson that uses concepts in population geography and cartography to fulfill several national geography standards.     

基于互联网信息的城市商业游憩网点空间竞争域划分研究

提出了一种基于互联网信息的空间竞争域划分方法。在Voronoi图的模型中尝试以网络平台数据作加权因子,使空间竞争域体现互联网中的消费者偏好差异,通过对加权Voronoi图的类型划分和地理学解释,描述竞争环境的空间特征。以北京市健身俱乐部为例,选择大众点评网、爱帮等网络平台信息作为权重因子,构建样本网点的传统Voronoi、互联网信息加权Voronoi计算模型并对比边界线、面积等空间特征分析的结果表明:互联网信息对城市商业游憩网点的空间竞争力产生着不同的影响强度,对Voronoi图空间特征的分类和地理解释可以指示商业网点跨越距离阻碍的消费吸引力及竞争差异,弥补传统加权方法未考虑消费者偏好和购物习惯而对竞争域划分表达不足的缺点。