MANIPULATING THE SPAWNING TIME OF THE AFRICAN CATFISH {CLARIAS GARIEPINUS) USING TEMPERATURE .AND PHOTOPERIOD | ||||
| Egyptian Journal of Aquatic Biology and Fisheries | ||||
| Article 2, Volume 5, Issue 4, September 2001, Page 11-28 PDF (956.69 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/ejabf.2001.1706 | ||||
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| Authors | ||||
| Gamal Abd El-Nasser1; El-Saved Shokr2; Nabii Abdcl-Hakim2 | ||||
| 1Central Laboratory of Aquaculture Research, Abbassa, Sharkia, Egypt | ||||
| 2Dept. Animal Production. Fac. of Agriculture, Al-Azhar University | ||||
| Abstract | ||||
| The possibility of manipulating the spawning time of the African catfish (Clarias gariepinus) was tested so that its fry could be produced and available all the year round.A total number of 120 of Clarias gariepinus immature females with an average weight of 80.52 ± 4.58 g were randomly divided into 8 groups and accommodated in 8 glass aquaria & 170 x 70x 50 cm each, representing 3 treatments and control (two replicates each). The first two aquaria (control) were subjected to the natural light (10L: 14D) and room temperature (18 - 21 °C). The second two aquaria (treatment 1) were also kept under same photoperiod as the control, however water temperature was increased and maintained at (27 - 28 °C). The third two aquaria representing treatment 2 were subjected to a longer photoperiod (I5L; 9D) and their water temperature was kept as low as the control. Water temperature of the last two aquaria (treatment 3) was adjusted and maintained as high as that of treatment 2 (27 - 28 °C), however the photoperiod was similar to that of the second treatment (15L: 9D). Fish were fed 6 days a week at a rate of 2% of the total biomass using 25% protein pelleted diet. Feeding quantity was adjusted according to the total biomass weekly. Samples offish were taken regularly from the odd aquaria to follow growth rate and check for maturity. Five samples were taken during the experimental run. The first sample was taken after 16 days from the beginning of the experiment. The second one was after 30 days from the beginning of the experiment The third was carried out after 45 days The fourth and fifth were after 55 and 70 days from the start of the experiment, respectively. The fish samples were scarified and ovaries were extruded carefully and weighed to calculate the gonadosomatic index. Whenever fish of any treatment reach maturity stage and become fully ripe, fish of the other aquaria of the same selected when they were ready to spawn and were artificially reproduced using injection with suspension of pituitaries of males from the same aquaria,After 30 days from the start of the experiment, treatment 1 (15L: 9D, & room temperature) reached the ripe stage earlier than the other ones, 40 days earlier than the control group. Thirteen females out of 15 with an average body weight of 95.4 ± 3.82g responded to the injection. After 45 days from the beginning of the experiment treatment 3 (15L:9 D & 27 - 28°C) followed Treatment 1. The spawning time of treatment 3 started 25 days earlier than the control. Twelve females with an average body weight of 96.0 ± 2.22 g were stripped successfully out of 15. After 55 days, treatment 2 (15L: 9 D & room temperature) was the third one to reach the ripe-egg stage 15 days earlier than the control Number of responding females was 11 with an average body weight of 97.1 ± 6.74 g. The last treatment that reached egg-ripening stage was the control after 70 days from the beginning of the experiment. Twelve females with an average body weight of 99.0 ± 5.26 g were injected and stripped. The mean values of egg/weight index percentage, fertilization percentage, hatching percentage and percentage of deformed larvae in the three treatments were not significantly different. Moreover, the spawning time of first group extended to overlap with that of the third one that extended in its turn to overlap with the spawning time of the second. The spawning time of the second treatment also extended to overlap with that of the control. Accordingly, there was an artificial spawning time (additional 40 days) that prolonged the natural spawning season and extended the availability ofClariasfry for, a longer period. Growth, gonadosomatic index, artificial spawning indices were also discussed. | ||||
| Keywords | ||||
| Spawning; Clarias. gariepinus; Temperature; Photoperiod | ||||
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