TY  - SER
AU  - EI-Gamal,A.A.
AU  - Amer,M.Abdel-Baky
TI  - Induced breeding of silver carp hypophthalmichthys molitrix (valenciennes) under the egyptian environmental conditions
KW  - Silver carp
KW  - Breeding
KW  - Larvae
KW  - Fish ponds
KW  - Environmental aspects
KW  - sexual maturity
N1  - Includes references
N2  - The reproductive performance of 181 female silver carps Hypopthalmichthys molitrix (Valenciennes) was followed up during 8 months (March-October) in two successive years, 2004 and 2005 under the Egyptian environmental conditions. To study their reproductive performance, ovulation was stimulated in females with two doses of a carp pituitary powder (Argent, Philippines, Manila): a preparatory dose (0.3 mg/kg) followed by a resolving dose of 4.0 mg/kg body weight after 9 h, whilst males were stimulated with one single dose of 3 mg /kg. Females were stripped approximately 7-8 h after the second injection and eggs were immediately fertilized 'dry method'. Fertilized eggs were incubated in conical shaped fiberglass tanks supplied with aerated fresh flow-through water. An attempt was also carried out to outline the age at maturity in 214 females during 2005. The monthly trend of spawning traits in terms of percentage of ovulated females, egg weight in grams and as a percentage of female's body weight, number of seeds per kg/fish, percentage of fertilized eggs, larval survival rate and percentage of deformed larvae were estimated. Highest female response to induced breeding and better larval quality were obtainable from April to June. Females of silver carp attained sexual maturity at a body weight of less than 2 kg and an age of two years old or less. The lowest percentage of spawned fish was recorded in March (66.7and 50.0% in 2004 and 2005, respectively). During other experimental months percentage of ovulated females was in the range of 83.3 to 100%. The latency time was approximately 7.5 h at a temperature of 25.5ºC. Stripped eggs as a percentage of female body weight (ESI) ranged from 6.87 to 15.75%. Relative fecundity of females was in the range of 61,070 and 156.440 eggs/kg. Hatching occurred after approximately 20 hours at 25.5 ºC water temperature. Fertilization and survival rates ranged from 85.91 to 97.86% and 72.72 to 80.72%, respectively. The lowest percentages of deformed larvae (1112%) were observed during April-May compared with either that obtained during the early season (March: 15-20%) or at the late spawning season (July-October: 16-18%)
UR  - http://nile.enal.sci.eg/EALE/2006/MUJAS/3106/5/2787.pdf
ER  -