摘要:

Abstract.Formalin is an effective fish chemotherapeutant which is used to control certain ectoparasitic and bacterial infections. It is toxic to fish and its pathological and physiological effects have been reported. An experiment was conducted to elucidate the possibility of retention of formaldehyde in the muscles of two tropical food fish species, following exposure to therapeutic levels of formalin. The results indicated thatPuntius gonionotus(Bleeker), retained 5·75 ppm formaldehyde following exposure to 50 ppm formalin for 24h. In contrast,Clarias batrachus(L.) retained 14·03 ppm and 18·72 ppm formaldehyde following exposure to formalin at 50 ppm and 100 ppm for 24 h respectively. However, no formaldehyde was detected after keeping the exposed fish in clean running water for 2

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00647.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.This paper studies maturity and spawning tendency of a hillstream catfish,Glyptothorax madraspatanum(Day), in the Western Nayar River, Garhwal, Central Himalaya, India. The fish is a protracted spawner as it spawns only once during the limited period from July to August. Fecundity ranges from 1640 to 6830 eggs and is more closely related to ovary weight and fish weight than ovary and fish length. There was a non‐significant sex ratio of 1:1·24 between males and femal

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00648.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Tench,Tinca tincaL., larvae were reared under controlled conditions at water temperatures of 28°C and 31°C during a 15‐day period. Feeding with exclusively liveArtemianauplii gave best results, irrespective of rearing temperature (total length 13·6mm; average weight 31 mg; survival rate 83–85%). High survival rates of 81–88% were found also in all groups fed mixed diets, whereas growth rate of tench larvae was significantly influenced by the frequency of supplemental feeding withArtemia.When applied alone, the tested carp starter feed turned out to be insufficient for rearing the larv

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00649.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.During the development of freshwater fish culture in Israel there has been a trend toward intensification, which has been accelerated in the last years with the introduction of new culture systems: deep reservoirs, fish cages and mechanically stirred ponds. In the present paper, the main processes affecting water quality variability in outdoor systems with increasing fish culture intensification levels are presented. The analysed systems are semi‐intensive shallow ponds with different organic loading, semi‐intensive shallow ponds with different fish species combinations, semi‐intensive deep reservoirs, and intensive mechanically stirred ponds. The examples are from experiments conducted at the Fish and Aquaculture Research Station Dor and from follow‐ups at fis

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00650.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The effect on the growth of freshwater angelfish,Pterophyllum scalare(Lichtenstein) (Pisces; Cichlidae), of different densities of population and diet compositions was studied. The results show that increasing the population density from 50 fish/m2to 200/m2significantly decreased the rate of growth of fingerlings, and that this effect is correlated to the size of fish. No significant differences were observed in growth between diets containing 37%, 41% or 47% protein. However, the addition of live food (artemia) to the diet significantly raised the growth rate, especially in the higher protein diets.Body composition shows no changes during the growth periods, with a mean of 64·68% body protein, 35·47% dry weight fat and no significant differences in the percentage of residual ash through the growth period.The food conversion rate was very low, ranging from 1·15 to 1·31. Total production increased with density, from 4·0g/m2/day (50 fish) to 13·7g/m2/day (200 fish) over a period of 60

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00651.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Nile tilapia,Tilapia nilotica(L.), were fed eight isonitrogenous diets in two laboratory experiments at the Faculty of Agriculture (Saba Basha), Alexandria University, Alexandria, Egypt. The diets were: (A) mixture containing 28% protein from both animal protein (fish meal) and plant protein (soybean meal and cotton seed meal) as a source of protein; (B) mixture free of animal protein; (C) mixture B supplemented with essential amino acids (EAA) (methionine and lysine); (D and E) composed of diet C supplemented with 5% and 3·5% oil respectively; (F and G) composed of diet C supplemented with emulsified or saponified 3·5% oil respectively and (H) mixture composed of diet C plus non‐extracted rice bran instead of wheat flour as a source of energy without adding oil.Growth performance (energy and protein retention and protein efficiency ratio) decreased with the animal protein free diet B. Supplementation of methionine and lysine to diet C improved growth performance and feed utilization as well as addition of oil and treated oil but 5% oil and 3·5% saponified oil increased mortality of the tingeriings by 46·27% and 20% respectively. Diet F gave the lowest mortality and the highest growth, energy and protein retention and protein efficiency

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00652.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Studies were conducted on the growth performance and development of one‐year‐old fingerlings of seven species in lake pen culture. It was found that the body weight and length of the fingerlings increased evenly with each passing month. Based on the increase of length, these 7 species could be categorized into two groups; while based on body weight gain, they could be categorized into three groups. The growth Index of power functional relations concerning the weight and length ranged between 2·8 and 4·0, indicating that the two growths were in parallelism. It was considered that the condition factors should be calculated withb‐value according to the differences of fish species and ages (month). The monthly average indexes of the length and weight increases of the seven species were cal

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00653.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.At all onthogenesis stages of the Oriental river prawn.Macrobrachium nipponense(De Haan), size heterogeneity has been traced within one egg clutch, at different developmental stages of larvae, young and adult individuals. The problem of predetermining heterogeneity is discussed. Uneven larval development of individuals from a single clutch is shown. Also, it is shown that the first to become adults are the individuals hatched from small eggs. Conclusion is made that in estimating development and growth heterogeneity the genetic factor has a primary nature. Available data accounting is essential for selective culturing of prawns under controlled conditions with the required growth characteristics.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00654.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Procambarus clarkiiGirard, a native freshwater crayfish species of Lousiana, USA, was found to harbour the crayfish plague fungus,Aphanomyces astaciSchikora, in its cuticle as a benign infection. Under certain conditions,P. clarkiidies as a result of this parasite, and theA. astaciinfection then becomes acute and can be transmitted toAstacus astacus(L.).Therefore, it is now shown that at least three different species of North American crayfish (Pacifastacus leniusculusDana,Orconectes limosusRaff, andProcambarus clarkiiGirard) can carry the crayfish plague fungus,A. astaci, can transfer the disease to other crayfish species, and under certain circumstances can die of its own infection.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00655.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Arctic charr.Salvelinus alpinus(L.), were fed a commercial diet with or without a supplement of 1% chromic oxide (Cr2O3) in fresh water at 8°C for 70 days. Supplementation of the diet with 1% chromic oxide did not affect the lipid composition of stomach contents, but did affect that of the faeces.Highest total lipid content in faeces was observed when fish were fed on the diet supplemented with chromic oxide. The proportion of triacylglycerols and free fatty acids increased in the neutral lipid fraction. The level of the dietary fatty acids 16:0, 16:1 and 18:1 increased, while 20:1 (n‐9), 22:1 (n‐11) and 18:2 (n‐6) decreased significantly (P<0·05) compared to the unsupplemented diet.Total viable counts (TVC) of aerobic microorganisms were somewhat higher in stomach contents when the charr were fed on the unsupplemented diet. In faeces from charr fed the unsupplemented diet, TVC were higher, by a factor of 10 compared to fish fed diet supplemented with chromic oxide. Bacterial composition in stomach content of both rearing groups were dominated byPseudomonassp. andAgrobacteriumsp., but the number ofLactobacillussp. andStreptococcussp. enhanced in stomach content when the fish were fed on the chromic oxide enriched diet. The faecal bacterial flora were also different between the rearing groups. The predominant bacterial species present in the faeces of fish fed unsupplemented diet were identified asPseudomonassp. andAeromonassp. Other bacterial species isolated includedLactobacillussp.,Streptococcussp.,Agrobacteriumsp.,Flavobacteriumsp. andVibriosp. In contrast, the bacteria flora in faeces of fish fed the chromic oxide diet was dominated by the Gram‐positive bacteriaStreptococcusandLactobacillus.It is suggested that the use of chromic oxide as a marker in digestibility studies in Arctic charr may not

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00656.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY