摘要:

AbstractThe morphological and physiological characteristics of the testes and the sperm of the catfishHeterobranchus longifilis(Val.) are presented. The effect of cryopreservation on the fertilizing capacity of the sperm was also evaluated. Testicular structure and spermatogenesis are described using histological techniques. The coexistence in the lobules of spermatozoa and all the spermatogenic stages indicates that this species is able to perform continuous reproduction. No seasonal trend was noticed in the evolution of the gonadosomatic index and in the quantity of the sperm produced over a year’period. However, maximum sperm production was observed in April and September.Different cryopreservation trials were conducted using a cryoprotective solution composed of 5% dimethyl sulphoxide (DMSO), 5% glycerol, 10% hen's eggyolk and 80% Mounib's solution. Fresh and cryopreserved semen gave equivalent hatching rates (81.1%, 83.4% and 78.9% respectively for the fresh, the 1‐hour cryopreserved and the 8‐month cryopreserved sperm). Percentages of normal and deformed larvae were not affected by sperm cryopreserv

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01239.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe growth dynamics of six different Swedish stocks (Arjeplog, Arevattnet, Bergnäs, Båthälla, Granbo. Gullspång) of landlocked brown trout were compared. The fish were kept in 1‐m2troughs from start of feeding in spring 1988 until September 1989. Thereafter the stocks were reared together in 4‐m2troughs until the termination of the experiment in October 1990. After the first summer of growth, Bergnäs trout had the highest mean weight and Granbo and Båthälla trout the lowest. In September 1989 the ranking of stocks with respect to mean weight had not changed. During the rest of the experiment, i.e. when stocks were reared together, Arevattnet trout increased in weight most rapidly and reached the highest final mean weight. Bergnäs trout grew very slowly after the stocks had been merged. Granbo and Båthälla trout ended up with the lowest mean weights. Sexual maturation in 1 + males was very rare. Gullspång trout had the highest proportion (42%) of mature 2+ males, while Granbo trout had the lowest proportion (4%). With the exception of Gullspång trout, mature males generally had a higher mean weight than immature fish.The experiment revealed considerable differences in overall growth, even between stocks with similar life histories in nature. Hatching time, frequency of sexual maturation and hatchery selection were identified as potential mechanisms behind the observed differences. In all, stock differences in important traits for commercial aquaculture are considerable, which makes further stock comparisons necessary before the start of bree

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01240.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractTropical catfish,Mystus nemurus(C.&V.) (25.89 ± 0.7 g) were stocked semi‐intensively in 0.03‐ha earthen ponds at the rate of 10 000 ha”‐1and fed six iso‐energetic practical diets ranging from 27% to 50% protein for 8 weeks. Each diet was fed in three replicate ponds twice daily to satiation. Experimental fish were also reared extensively, in control ponds, without supplementary feed. Fish fed the 42% protein diet had the highest standing crop, weight gain and protein utilization values and the differences from other diets were statistically significant (P>0.05). Protein efficiency ratio (PER) decreased as dietary protein increased. The experiment indicated that natural food organisms contributed to some degree if not significantly to the catfish production. Weight gain, food conversion ratio (FCR). PER and SGR (specific growth rate) indicated that a 42% protein diet with digestible protein‐to‐energy ratio (D/E) of 27.57 mg kj_1produced maximum growth in the stat

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01241.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThree components of the energy budget, consumption (C), respiration (R) and growth (G). were measured in larval and early juvenile sole (77 μg to 7.2 mg dry weight) kept under controlled temperature (15oC), light (photoperiod 18 h at 800 lux) and food (Artemici salina.5 ind ml‐1) conditions.The increase in body weight with age is described by the growth functionWt= 51.9 e0143t, wheretis time in days from hatching.Wtis weight (ug dry wt) at time t, 51.9 is the estimate of larval weight at hatching (Wo) and 0.143 is the instantaneous growth coefficient. Daily food consumption (C, in ug dry wtday”1ind‐1) increased with body weight (W, in ug dry wt) according to the allometric function, C = 1.852W0.852. Low routine oxygen consumption (R, in nl 02h‐1ind‐1) was best described in relation to body weight by the allometric equationR =1.47W0.975By using the above growth and allometric functions and by converting G,Cand R into their energetic equivalents (joules day‐1ind‐1), the changes in assimilation efficiency (K1) and gross growth efficiency (K1) during ontogeny cou

ISSN:1355-557X    

DOI:10.1046/j.1365-2109.1996.t01-1-00800.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractJuvenile pikeperch 3.66 ± 0.23 cm total length (TL) and 0.32 ± 0.05 g were reared in water at 22 ± 0.5°C and fed with live zooplankton or alternatively a commercial trout feed. Fish fed with dry diet grew faster and had higher condition factor than fish fed live zooplankton. Sex differentiation in pikeperch was visible at different stages of ontogenesis, but was related to the fish growth rate. The gonads offish that were 3.43‐5.69 cm TL revealed undifferentiated characteristics. Clear indication of oogenesis in females was observed in pikeperch at 7.9 cm TL and 3.47 g, whereas evident spermatogenesis was not observed till the end of the exper

ISSN:1355-557X    

DOI:10.1046/j.1365-2109.1996.00801.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractInduced spawning in Eurasian perch,Perca fluviatilisL., was studied using human chorionic gonadotrophs (hCG) or acetone‐dried common carp pituitary with or without hCG. The dose administered to fish was 5700 IU hCG kg‐1or 4.0 mg kg‐1carp pituitary with or without 500‐700 IU hCG kg‐1for females and 2850 IU hCG kg‐1or 2.0 mg kg‐1carp pituitary with or without 250‐350 IU hCG kg‐1for males. There were no statistically significant differences in quantity of milt in treated and control groups, although the best result was observed when males were treated with a triple injection of hCG and carp pituitary extract. Male spermiating success, expressed as a quantity of milt, was negatively correlated with fish weight. All females treated in this experiment had oocytes at the same division, so time of ovulation was highly synchronous. Spawning success, expressed as a spawning effectivity coefficient (Sc), was highest in fish treated with the triple injection. Spawning methods described in this paper were successful, even though hormones from another order

ISSN:1355-557X    

DOI:10.1046/j.1365-2109.1996.t01-1-00802.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractIn the summer months, epizootics occurred regularly among larvae ofPenaeus indicus(Milne Edwards) in a hatchery located at Narakkal near Cochin, India. The clinical signs of infected larvae were expansion of chromatophores. opaqueness of body with twisting and degeneration of appendages. Bacteria were isolated from the infected larvae. These bacteria had morphological, physiological and biochemical characteristics of the genusVibrio,but these properties did not correspond with those of knownVibriospecies. TheVibriowas most related toVibrio campbelliiaccording to DNA‐hybridization experiments. By pathogenicity experiments, the presentVibrioisolate was proved to be pathogenic to larvae, postlarvae and adult shrimp. Shrimp larvae challenged by immersion showed significant mortalities. The bacterial isolate failed to produce the infection in adult shrimp after oral inoculation but it caused significant mortality in adults after intramuscular injection. LC50and LD50values of theVibrioisolate were determined for larvae and adult shrimps, respectively, at different time interval

ISSN:1355-557X    

DOI:10.1046/j.1365-2109.1996.t01-1-00805.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractInterest in the cultivation of wolffish arose in recent years due to their high‐quality meat and fast growth in captivity. In wolffish, an almost juvenile organism, more than 20 mm long, hatches from the egg and can be fed dry pellets just after that. This makes the technology for wolffish breeding much simpler than for other marine fishes, even salmonids. This paper is devoted to common wolffish.Anarhichas lupusL., as the captive breeding of this species has been studied most completely. Experience with broodstock management, insemination, incubation of eggs, start feeding, and growth of rearing juveniles until maturation is described, based mainly on investigations made in Norway and in the Russian Federation. The conditions for obtaining maximum production in the shortest time are assessed. Prospects for using wolffish in aquaculture are briefly discusse

ISSN:1355-557X    

DOI:10.1046/j.1365-2109.1996.00810.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractSea bass,Dicentrarchus labrax(L.), juveniles (1.32 g) grew at a rate of 4.2% per day, when fish were fedad libitumand reared at optimal thermal conditions (ambient sea water temperature, 20‐26°C). At 13°C, feeding and spontaneous activity were severely restricted and somatic growth was reduced to 0.6% per day. Over a period of 6 weeks, both muscle fibre hyperplasia and nuclear division were higher in the ambient‐temperature group compared with the fish reared at 13°C. Despite the differences in growth rate and spontaneous activity, muscle fibre hyperplasia was paralleled by nuclear division in the lateral axial muscle in both temperature groups and the number of nuclei per myofibre did not differ significantly between the two temperature groups. It is concluded that at optimal thermal and feeding conditions, somatic growth of sea bass juveniles is mediated through an increase in the number of nuclei and muscle

ISSN:1355-557X    

DOI:10.1046/j.1365-2109.1996.t01-1-00819.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:1355-557X    

DOI:10.1046/j.1365-2109.1996.t01-1-00838.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY