摘要:

AbstractThis paper provides an overview of the structure and performance of Chinese integrated pond fish farming systems, based on analysis of survey data for 1013 ponds on 101 farms in eight Chinese provinces. A province‐by‐province examination of gross and net fish yields supports the traditional Chinese classification of provinces into high, medium and low productivity classes according to fish farm output: average net fish yields for surveyed ponds in each class were 7958,4981 and 3321 kg ha−1year−1respectively. The paper includes summaries and analyses of data on fish stocking and harvesting, use of feeds and fertilizers, fish‐animal integration, capital inputs, and the overall cost and revenue structure in each productivity class. In addition to variations in aggregate input and output levels, a key difference between productivity classes is seen to lie in the stocking model utilized: filter‐feeding fish dominate in poorer areas, while ‘feeding fish’ (grass carp,Ctenopharyngodon idella(Valenciennes), black carp,Mylopharyngodon piceus(Richardson), and omnivorous carps) dominate in high‐productivity provinces. These results are examined in light of regional differences in culturing tradition, socio‐economics, infrastructure, climate and g

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00887.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIt is important that we should encounter the accurate use of statistical methodologies in aquacultural research. To assess the quality of statistical use in aquaculture, a sample of papers published between 1981 and 1991 was examined from two aquacultural research journals. A total of 180 papers were screened with regard to the chosen study design, the data description. the choice of sample, the analysis methods used and the presentation and interpretation of results based on the statistical methods employed. The results of this examination demonstrated that only a small number of papers contained fully informative statistical expositions. Designs of studies were often only partially described and insufficient summaries of collected data were frequently given. Incomplete analyses and poor presentation of results also occurred frequently. Interpretations of statistical results were not always satisfactory, some papers instead discussing results from alternative studies. Basic requirements for the description of statistical inputs in scientific literature are emphasized and a list of publications is given recommending statistical techniques appropriate for aquacultural research.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00888.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractResults are reported of the growth and yield of the Malawi chambo,Oreochromis karongae(Trewavas, 1941) association, andOreochromis shiranus(Boulenger. 1896) in polyculture withClarias gariepinus(Burchell. 1822). Six ponds of 150 m2were assigned to two replicates of three treatments:C. gariepinusandO. shiranus; C. gariepinusand chambo spawned on station;C. gariepinusand chambo collected from the lake. Total fish stocking density was 3 m−2, and stocking ratio 1:2 (C. gariepinus:titapias). Initial mean body weights were 10.9 g forO. shiranus.13.2 g for C.gariepinusand 13.3 g for chambo.The ponds were fertilized with chicken manure at the rate of 13.5 kg dry matter ha−1day−1, representing the daily NPK loading of 0.618.0.186 and 0.191 kg ha−1, respectively. Maize bran was applied at 3% body weight day−1for 168 days.Fish growth rate forC. gariepinuswas significantly higher (P0.05) in the growth of chambo despite the source of fingerlings. More fish biomass came fromC. gariepinusstocked at 1 m−2than from the tilapias stocked at 2 m−2. Extrapolated fish yields in the range of 4.37‐4.75 t ha−1year−1were obtained from the polyculture of chambo andC. gariepinus. Oreochromis shiranusandC. gariepinusgave 3.95 t ha−1year−1.Low water temperatures for 112 days slowed the growth of tilapias but did not seem to inhibit the growth ofC. gariepinus.Chicken manure and maize bran, applied at smallholder farmer's level, has produced higher yields than by usingO. shiranusin monoculture at optimal temperatures. The yields obtained show that the polyculture system is feasible during the cold season and may justify investment in aquaculture

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00889.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe objective of the present study was to evaluate the effect of fish meal quality on growth, feed conversion and protein utilization in common wolffish.Anarhichas lupusL. The study involved comparison between low‐temperature‐processed (Norse‐LT) and regular fish meal (NorSeaMink) included in dry pellets. Results obtained for these dry feeds were compared with those obtained using moist feed containing squid mantle. The results show better growth rate, feed conversion factor, protein efficiency rate, (PER) and productive protein values (PPVs), when using low‐temperature‐processed meals compared with regular fish meals in feed to wolffish. No specific differences were found in growth rate and feed conversion factor between fish fed diets containing low‐temperature‐processed meal or squid mantle. Whole body lipid content was highly influenced by dietary content. No effect of dietary moisture content was demonstrated

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00890.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA production model is presented for semi‐intensive freshwater crayfish culture ponds incorporating detrital forage. The conceptual model is developed from five submodels of trophic‐dynamic interactions within the pond ecosystem. The model includes microbially enhanced detrital forage (MEDF) produced from plant matter grown in the pond as a significant component of nutrition. The model is proposed as an aid to understanding pond‐based aquaculture techniques that rely upon manipulating the characteristics of MEDF. The significance of MEDF as a source of nutrition in aquaculture is disc

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00891.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractGenetic variation in susceptibility of Atlantic salmon,Salmo salarL., to furunculosis, bacterial kidney disease (BKD) and cold water vibriosis was studied by challenge testing one‐year‐old fingerlings. Fish from 81 full‐sib families within 32 sire progeny groups were infected withAeromonas salmonicida, Renibacterium salmoninarumandVibrio salmonicida.Estimated heritabilities were relatively low, being highest for BKD (h2= 0.23) and lowest for cold water vibriosis (h2= 0.13). Genetic correlations between the ability to survive the diseases were all positive, but the magnitude of the genetic correlation between furunculosis and BKD may be biased upwards because some of the dead BKD fish were also infected with furunculosis.The application of selection to develop resistant populations of Atlantic salmon is advocated. Challenge testing seems to be a feasible method, with relatively low costs and easy management. The future response to selection will depend on the relationships between results from a challenge test and mortalities under farming conditions and between disease resistance and other traits in the breeding

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00892.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractMethods were determined for the induction of diploid gynogenesis in the sole,Solea solea(L.), in order to investigate the sex‐determining mechanism. The experiments utilized gametes obtained by dissection of fish caught at sea. Activation of eggs with UV‐irradiated sole sperm was not feasible but development was initiated by exposure to halibut,Hippoglossus hippoglossus(L.), sperm. These embryos displayed the typical characteristics of haploids and few survived beyond hatching. High levels (>90%) of diploidy were induced in such eggs by subjecting them to a cold shock (2°C or 4°C) for 1‐2 h about 10‐15 min after activation at 12°C. The resultant embryos were indistinguishable from those developing from normally fertilized eggs and were considered to be diploid gynogenomes. Fifteen of these were reared to a length of 5‐10 cm by which time gonad differentiation had been initiated. Both sexes were represented, indicating that sex in this species is not determined by a simple XX‐XY system with f

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00893.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThree isonitrogenous and isocaloric rations containing various levels of commercially dehulled soybean meal as replacement for menhaden fish meal were fed to four replicate groups of channel catfish,Ictalurus punctatus(Rafinesque), fingerlings, mean initial live weight 13. 7 g, in 0.4‐ha earthen ponds for 114 days. As fish meal was removed from the experimental diets, vegetable fat, soybean meal, and inorganic phosphorus were increased to maintain 35% crude protein, 11. 7 Mj of digestible energy (DE) per kg, and a minimum of 0.45% available phosphorus.The percentage of the whole body weight made up of dressed carcass, head, skin and viscera did not vary significantly among dietary treatments. Average values for dressed carcass, head, skin and viscera were 60.8%, 20.8%, 6.7% and 9.7%, respectively.The chemical composition of the various body parts was not significantly affected by diet. Average fat percentages for dressed carcass, head, skin, and viscera were 8.2%, 7.3%, 16.0% and 26.4%, respectively. Average protein percentage were 15.7%, 14.9%, 22.2% and 11.4%, respectively.These results indicate that varying the percentage of fat added to a practical catfish diet from 0% to 3.8%, but holding the DE constant, will not affect dressing percentage or body composition of the fed fis

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00894.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00895.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY