摘要:

Abstract.Semi‐purified casein/gelatin diets containing two levels of lipid (5 or 10%) and three levels of reduced glutathione (0,0·1 or 1·0%) in a factorial arrangement were fed to fingerling channel catfish,Ictalurus punctatus(Rafinesque), in aquaria for 10 weeks. Factorial analysis of variance indicated that dietary lipid had significant (P<0·05) effects on growth, feed efficiency and body composition of channel catfish. Diets containing 10% lipid generally produced higher weight gain and feed efficiency values as well as higher intraperitoneal fat. The higher level of dietary lipid also produced lower moisture and higher lipid (on a wet‐weight basis) levels in whole‐body and fillet tissues. Stability of fillet samples was estimated by 2‐thiobarbituric acid (TBA) analysis which revealed that 10% dietary lipid significantly elevated fillet TBA values while glutathione did not have any effect. Therefore, dietary lipid level altered growth and body composition of channel catfish as well as oxidative stability of fillet samples while dietary glutathione was generally i

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00620.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Growth and survival were compared among uniform‐ and mixed‐age groups of Florida red tilapia fry during sex reversal in brackishwater (12ppt) tanks, under commercial‐scale hatchery conditions. Three treatment groups of post‐yolksac (i.e. free‐swimming) stage fry of different age compositions were compared: (1) 100% fry collected at the free‐swimming stage (FSF); (2) 100% fry obtained through artificial incubation of eggs and non‐swimming sacfry (ENS); and (3) a mixed group consisting of 50% of each type (FSF+ENS). Fry were stocked into 530–1 cylindroconical tanks at a density of seven fish/l (3700/tank) and reared on an androgen‐treated diet for 30 days. While specific growth rates (range = 17·1–17·8% body weight/day) did not differ (P>0·05) among treatments, significant (P<0.05) differences were observed for survival and feed conversion ratio (FCR). ENS showed highest survival (76·8%) and lowest FCR (1·14), FSF showed intermediate survival (59·2%) and FCR(l·33), while the mixed‐age group (FSF+ENS) showed lowest survival (38·5%) and highest FCR (1·70). Under all treatments, a majority of fry losses were attributed to cannibalism. A highly significant (P<0·001) negative regression between survival and coefficient of variation of initial weights (CV = SD/X̄) indicated that cannibalism was reduced by minimizing age/size variation at stocking. The CV of initial weight may be a useful parameter for predicting fry survi

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00621.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The satiation time, stomach capacity, gastric evacuation rate and return of appetite were investigated inClarias gariepinuslarvae. The evacuation of food from the stomach was described by the exponential model. Gastric evacution was found to be inversely related to return of appetite. Both satiation time and feed intake as a % of body weight were found to increase rapidly over the first few days of larval feeding, after which they remained constant. A simple model is proposed for the estimation of maximum feed intake in relation to feeding scheduled and feeding frequency forClarias gariepinuslarvae.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00622.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Two grow‐out experiments were conducted to evaluate the functional role of chicken manure for Nile tilapia,Oreochromis niloticus(L.). production in central Thailand. Experiment 1 examined the relationship between chicken manure input and net fish yield (NFY). Experiment 2 determined the value of chicken manure in providing tilapia particulate organic carbon, and/or dissolved inorganic carbon (DIC) for stimulating algal productivity. In both experiments supplemental urea and triple superphosphate (TSP) gave all treatments total nitrogen (N) and phosphorus (P) inputs of 28·0kg/ha/week and 7·0kg/ha/week, respectively.Addition of chicken manure to inorganic fertilization did not enhance production of Nile tilapia. NFY in experiment 1 increased with decreasing manure loading, which corresponded to increasing TSP input. Regression analysis suggested that chicken manure‐P was about 10% effective as TSP‐P at increasing NFY. NFY was linearly correlated to net primary productivity (r2= 0·62,P<0·001), which was linearly correlated to total alkalinity (r2= 0·77.P<0·001).Treatment differences in alkalinity, community respiration or dissolved oxygen concentrations at dawn were not related to manure input. Simple economic comparisons discourage the purchase of chicken manure as a source of soluble N and P for increasing algal productivity

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00623.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The results of population genetics studies associated with the problem of the restoration of Atlantic salmon,Salmo salarL., in Russia are presented. The peculiarities of using donor material for artificial population formation when the native gene pool has been lost are discussed. Genetic polymorphism in 19 salmon populations from different areas (within Russia) were investigated and analysed. Intrapopulation genetic differences of the Pechora River Atlantic salmon are shown. The role of monitoring in salmon culture is discussed and the results of an ecologo‐genetic evaluation of natural and artificial salmon populations are presente

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00624.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Larvae ofRana pereziSeoane were reared under laboratory conditions on three compounded diets, three fresh diets and three mixed diets in an attempt to compare the nutritive use and the relative performance of the feeds. The indices of nutritive use help to evaluate the diets. Best digestibility was observed with the fresh diets, although the animals grew slowly. A diet rich in protein (40%), fats, and carbohydrates improved growth rates.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00625.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The relationship between absence of functional swim‐bladder, calculosis and larval mortality of hatchery‐reared sea bream,Sparus aurataL., was observed. There was a temporal variation in the main causes of mortality, i.e. not inflated swim‐bladder appears to be the main cause up to the 47th day, and the presence of calculi around the 55th day. Histological sections, semi‐quantitative analysis and scanner electron microscope photographs were carr

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00626.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Commercial slaughtering of eel sold fresh starts with the so‐called ‘neck‐cut’. This tran5ectlon of the spinal column separates the spinal cord from the brain. In due course the slaughtering process is completed by gutting, skinning and, finally, by decapitation. There is a widespread belief that the advantage of the neck‐cut is that it causes immediate death. However, inspection of eels with a neck‐cut revealed no visible injury to the brain. Repeating the method as a laboratory experiment and subsequent observation of the experimental eels resulted in spinal regeneration, as reflected by behavioural recovery through four stages in about 6 weeks. It seems that after the neck‐cut the brain is still intact, both structurally and functionally, and remains so as long as the slaughtering has not been completed. Thus a prolonged state of suffering cannot be ruled out. Consequently, slaughtering of eel should include instant destruction

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00627.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Growth rates, condition indices and diet composition of the Japanese oyster,Crassostrea gigasThunberg, were studied in two types of ponds which form part of a fish‐bivalve integrated culture system. Although abiotic parameters (e.g. temperature, salinity, pH, ammonia, particulate inorganic matter) were similar in the two pond types, oysters supplied with water from a sedimentation pond grew significantly faster and showed better condition indices than the oysters supplied with water from the PVC‐lined ponds. It is suggested that the main reasons for the better performance of the oysters supplied with water from sedimentation pond water are: higher algal diversity, additional nutritious Food consisting of attached benthic diatoms and stable algal concentrat

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00628.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Infestation parameters for the calígíd copepodLepeophtheirus salmonis(Kroyer) infesting sea trout,Salmo truttaL., were established for a number of locations off the west coast of Ireland during 1990 and 1991. Based on these parameters sites were classified into two groups in 1990 and three in 1991. Median parasitic intensity in these groups was 11·6 and 77 in 1990 and 9·5, 29·5 and 55 in 1991. Fish were parasitized mainly by chalimus stages of the parasite which attached preferentially to the fins. Heaviest infestations were invariably due to chalimus stages and early pre‐adult lice and there was a progressive decrease in the correlation between parasitic intensity and the number of each successive stage in the life cycle. This suggested either host or parasite mortality as the parasite matured. Large numbers of lice‐infested fish returned prematurely from the sea to estuarine areas at a number of sites. Extensive morphological damage, especially to the fins, was apparent on a proportion of these fish as a result of the infestation. Mortality of heavily infested fish was directly

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00629.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY