摘要:

AbstractIn order to obtain an appropriate and reliable method for the mass production ofClarias gariepinus(Burchell) fingerlings. experiments on artificial reproduction and pond rearing were carried out in the Republic of Congo in 1987‐1991. Reproduction could be induced throughout the year using common carp pituitaries (3 mg kg−1female). The average relative fecundity of females varied between 1.3%± 0.3 (SEM) and 14.3%±1.3 (SEM). The average hatching percentage of the eggs varied between 28.4%± 4.5 (SEM) and 59.1%± 3.7 (SEM) respectively, in the dry and rainy season. The fluctuation of the relative fecundity as well as the fluctuation of the hatching percentage follows the seasonal fluctuation in rainfall and temperature. The use of a net cage made of mosquito netting (1 m3, 0.5 mm mesh size) and the roots of water hyacinth (E. crassipes)as an egg incubator proved to be reliable. In ponds not protected against frogs an average of 5.0 ± 2.9 (SEM) fingerlings m−2per 40 days cycle were obtained, whereas in ponds completely surrounded by a wall of aluminium roof plates (0.8 m high) the average production was 32.3 ± 3.3 (SEM) fingerlings nr‐ per 40 days cycle, when they are stocked with approximately 100 larvae m−2. Increasing the larval stocking density or extending the rearing period did not improve the final production. The main causes of low production in unprotected ponds are competition for food resources due to the presence of phytophagous frog larvae and cannibalism among the fingerlings ofClarias gariepinus.An analysis showed that the system is labour orientated, technically reliable and economically feasible when the fingerlings can be sold for

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00908.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractHatching rates and hatching times (50% hatch) of red sea bream,Pagrus major(Temminck&Schlegel), eggs in culture media that were prepared to dilute rotiferBrachionus plicatilisMuller extract at 4000‐, 6000‐. 8000‐ and 10 000‐fold with artificial sea water (σ15, = 24.0) were investigated. Although differences in hatching rate between the culture media and control artificial sea water were negligible, hatching time was significantly shorter in media at 4000‐ and 6000‐fold dilutions than in media at 8000‐ and 10 000‐fold dilutions and in the control artificial sea water, when the eggs immediately post spawning were incubated. The hatching rates of eggs at three developmental stages, immediately post‐spawning, gastrula stage and heart‐beat initiation stage, incubated respectively in the medium at 6000‐fold dilution and the control, did not differ either, yet the hatching times at each egg stage in the medium were significantly shorter than that in the control. These results suggest that hatching enzyme secretion from the hatching glands is promoted to perceive chemical stimuli in the water‐soluble fraction of rotifer extract via the embryo's chemoreceptors, from the heart‐beat initiation stage to immediately before hatching, thus sh

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00909.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSimulated depuration trials with Manila clams.Tapes philippinarumAdams and Reeve, were undertaken to test the effect of stocking density, seasonal temperature, water flow rate, salinity and the addition of cultured algae on oxygen levels and some other variables of water quality. Equations produced by multilinear regression analysis provided useful systems‐management information for predicting the conditions required to maintain oxygen levels within known limits for satisfactory depuration of other commercial species of bivalve molluscs in temperate climate

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00910.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAn experiment was carried out to study the effects of anaesthetics (2‐phenoxyethanol, quinaldine sulphate, metomedate and MS‐222) on water parameters during simulated air transport of platyfish.Xiphophorus maculatus(Günther). The platyfish were put in sealed plastic bags, one‐quarter full of water, to which a required amount of anaesthetic was added. The rest of the bag was filled with oxygen. The water in the bag was tested for pH. total ammonia and carbon dioxide at intervals of 4 and 8 h for a period of 48 h. Mortality rates within this period and the post‐packaging period were also noted. It was found that 2‐phertoxyethanol was most effective, followed by quinaldine sulphate, in decreasing the excretion of metabolic wastes by the fish. Metomidate had no effect in the control of waste production. MS‐222 reduced ammonia excretion but not carbon dioxide. None of the anaesthetics used had any effect on the pH

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00911.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWhile physiological stress in fish can be assessed by several laboratory‐based methods, many of those methods use very sensitive and expensive instruments, which make them impracticable under field conditions. The objective of this study was to determine the feasibility of detecting stressed states in fish, under Held conditions, using simple but reliable methods. The first set of experiments were conducted in the laboratory, where a standard handling stressor was applied to juvenile coho salmon,Oncorhynchus kisutch(Walbaum). Results of blood samples analysed by both laboratory‐based and portable methods (e.g. glucometers for diabetic patients) were in good agreement. The second set of experiments focused on field‐testing the most promising methods based on the laboratatory tests. Production lots of Atlantic salmon.Salmo salarL., at commercial fish farms were sampled to assess stress and health status with the selected field techniques, from the swim‐up to smolting stages. The measured variables included: blood glucose, protein, haemoglobin concentrations: haematocrit: erythrocyte and lymphocyte numbers: and an autopsy‐based health profile, which involved the internal and external examination of the body for texture and colour. In addition to establishing resting, or normal, values for each variable under field conditions, blood glucose levels were observed to increase significantly at 4 h after a stressful event (e.g. grading, handling) using these field methods. Some of these field techniques were found to be reliable indicators of stress in fish and have potential for use in aquaculture facilities and field monitoring p

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00912.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.tb00913.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.tb00914.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.tb00915.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Books Reviewed in this Article:Sea Bass ‐ Biology, Exploitation and Conservation. Fish and Fisheries Series 12 (series ed. T. J. Pitcher). By G. D. Pickett&M. G. Pawson.Fisheries Processing: Biotechnological Applications. Edited by A. M. Marti

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00916.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY