Growth Evaluation of Four Local Strains of Nile Tilapia (Oreochromis niloticus) Under Different Farming Conditions in Egypt
2/5/2000
H. A. Elghobashy*, Abdel Rahman A. El Gamal** and A.M.Khater*
*Central Laboratory for Aquaculture Research
**ICLARM Regional Research Center for Africa and West Asia
Abbassa, Abou Hammad, Sharkia, Egypt
ABSTRACT:
Four local stocks of Nile tilapia,Oreochromis niloticus collected from different locations in Egypt have been evaluated for production performance in earthen ponds, rice fields and in an intensive system in enclosures. When daily average weight gain per fish was compared, Maryout strain had the highest yield in the pond study followed by the Abbassa stock. Maryout strain had the highest daily weight gain under pond and cage culture, but it perform poorly under rice-fish culture. Even though the Aswan population had the smallest initial size in the rice fields evaluation, it performed clearly better than the Maryout stock. Manzala strain had the highest daily weight gain under rice-fish culture. Data obtained illustrate genetic x environment interaction. We may conclude at this point that the Maryout strain is expected to perform better under pond culture and relatively better in intensive situations such as cages, while Manzala and Aswan strains are recommended for shallow culture systems such as rice fields.
INTRODUCTION:
Historically, fish culture in Egypt goes back to the earliest of civilization on the banks of River Nile. The first recorded history of fish keeping in ponds in Egypt is depicted on the walls of the Tomb of Thebaine. There is also reference to these early practices in the Christian Bible. However, the present aquaculture system began expand noticeably in the 1960’s to 1970’s when a scientific base for aquaculture development were practiced.
Currently, aquaculture in Egypt has become increasingly important in providing a immediate source of animal protein for the country’s growing population. The annual animal protein consumption is slightly less than 25 kg per capita, of which one-third is fish. The total fish production has reached 545,593 tons on 1998. The contribution from aquaculture exceeded 25% of the total fish production in the same year (139,389 tons).
Tilapias, are widely accepted to Egyptian consumers. To producers, tilapia represent the species of choice due to its high growth rate, significant tolerance to environmental stresses, ease of reproduction, and its unquestionable market demand. Nile tilapia, Oreochromis niloticus, in particular is considered the leading tilapia species in the country. Therefore, its contribution demand research activities in different areas of aquaculture. Starting in the 1980’s, the national awareness of the importance of aquaculture research to the economy was translated into actions. The research on pond management and reproduction aspects began earlier before the importance of genetics in the improvement of tilapia performance under different culture systems was realized. Scattered research projects in the area of genetics have been conducted in Egypt over the last few years. (El Sheakh et al., 1995; Green et al., 1995; Esmail, M., 1997).
Aquaculture is being practiced in different forms in Egypt. Earthen pond aquaculture is the major type of aquaculture in Egypt where only waste lands are allowed to be used for fish mainly because of their high salt and alkali content and poor drainage. Within 1-2 years of water flooding, soil salts are leached, thereby aquaculture is considered as a productive and temporary means of desalinating new lands (El Gamal, 1997).
Integrated agriculture/aquaculture is an ideal system in regard to the efficient use of production elements especially water. About 98,000 hectar of rice have been cultured with fish in Egypt during 1998 producing about 12,440 tons of fish. Common carp, Cyprinus carpio, is almost the only cultured fish in rice fields. However, only Common carp fry are the only available fish at affordable size that could be used in rice -fish culture resulting in relatively small harvestable size. Normally average size is about 1 gram upon stocking and about 70 g upon harvesting. Initial attempts have been started to cultivate tilapia in rice fields instead of common carp. Results are not available yet. Although rice-fish culture is significant element in Egyptian aquaculture, there is still a good opportunity for more development of that type of integrated system especially if strains of tilapia that can perform better in such system can be developed. It may worth mentioning that identifying strains that perform well in short growing season will add considerably to fish production in Egypt.
Cage culture is a type of aquaculture that has experienced fast development over the last two decades in Egypt reaching 1,540 cages in 1990, but declining afterwards to 1,294 cages, producing 2,855 tons in 1998. (GAFRD, 1999). Although cage culture contributes significantly to aquaculture in Egypt. There Is a great potential for more production. Therefore, identifying the best strain of tilapia -which is the only species cultured in this system will add significantly to the overall production from aquaculture.
Eknath et al., (1991) evaluated the growth rate of 8 strains on Nile tilapia under different culture conditions (ponds, rice fields and cages). The results indicated high significant difference among strains. Also interaction between the strain and test environment was low but significant.
Kamel, (1999) conducted a study on genetic evaluation of three strains of Nile tilapia collected from different geographical locations in Egypt under pond culture. There were a significant different on growth performance over the three strains of Nile tilapia . The Maryout strain perform better than the other two strains.
Objective of the study:To evaluate four strains of Nile tilapia for performance under different culture conditions, namely; ponds, enclosures and shallow systems (rice/fish culture).
MATERIALS AND METHODS:
Fish: Four local stocks of Nile tilapia, Oreochromis niloticus were collected by CLAR from different geographical locations in 1998 in Egypt.The Aswan stock was obtained from Lake Nasser hatchery, the Maryout stock was obtained from the region southwest of Alexandria and the Manzala stock was obtained from the northern part of the Nile Delta. These three stocks along with the local stock that was collected at Abbassa were evaluated. The four brood stocks were spawned during 1998 as well as during 1999 providing overwintered fingerlings as well as young-of-the-year fry to use in the current study.
Pond study: twelve 1000-m2 earthen ponds were allocated to the study in a 3-replicate experiment. Ponds were prepared, screened using fine mesh screen, filled and then stocked with the four stocks at random. Ismaelia Canal water was the source of water for this study. Water was only allowed to compensate water losses resulting from evaporation and seepage. The stocking density was 2/m2 (2000/pond). Ponds were stocked throughout 9 -16 August, 1999. After a mean of 115 growing days, ponds were harvested by complete draining. Fish were counted and collectively weighed. Average weight was obtained out of sub-samples. Yield and survival rates were obtained.
Integrated rice-fish culture: a piece of agricultural land of about 8000 m2 was prepared as a rice field. The whole area was divided into 12 plots and three 500-m2 plots were allocated as replicates to each stock of fish at random. Each of the plots was furnished with an appropriate ditch of 50 cm depth. The plots were seeded with rice as in normal rice culture then stocked with fish during the period from July 26 to August 03, 1999 at a rate of 200 fingerlings/plot except Manzala strain was stocked at a rate of 175 per plot due to an insufficient number of fingerlings. Upon the end of the rice season, plots were drained and fish were recovered during the first week of October, 1999 .The fish were counted and collectively weighed. Average weight was obtained out of sub-samples. Yield and survival rates were obtained.
Hapa Study: because of the limitation to have a suitable site for regular cages, it was decided to use hapas suspended in one of the 1000-m2 earthen ponds. The dimension of hapas used was 200 x 100 x 50 cm, representing length, width and depth, respectively. 12 hapas have been allocated to the four stocks in a 3-replicate experiment. Hapas were stocked during the period 28 July to 2 August, 1999 and fish were grown for an average of 98 days. After harvest the fish were counted and collectively weighed. Average weight was obtained out of sub-samples. Yield and survival rates were obtained.
During the whole study, fish were fed 25% protein commercial diet at rate of 3% of body weight for pond and cage culture. Fish at rice-fish culture were not feeded.
Statistical Analysis: Duncan's Multiple Range Test was performed on the data analysis of fish production in different culture systems.
RESULTS AND DISCUSSION
As presented in Table 1, Maryout which began with the highest initial weight in the earthen ponds had the highest yield 178.5 (kg/pond) followed by Abbassa stocks 142.3 kg. Also, Maryout had the highest daily gain either for fish 0.8 g/fish/day or for pond 1.54 kg/pond/day. Although there was some difference in regard to the duration of the experiment, especially for Manzala stocks which had the shortest growing period, such difference falls in December, at harvest dates, whereas growth has most likely declined considerably or stopped. This will make such difference of less important in the current comparison. When the four populations were ranked according to average daily gain per pond, the Maryout population came higher. It may worth mentioning that Eknath et al., indicated the limited importance of the effect of differences in initial size on subsequent growth performance of fingerlings under communal stocking. In absolute figures, Maryout had 1.54 kg/pond/day, followed by Abbassa, then Manzala and finally Aswan. These results are in agreement with results found by Kamel 1999 in genetic evaluation of three strains of Nile tilapia collected from different locations in Egypt. The Maryout strain had higher growth performance than other strains (Zawia and Abbassa), when they were reared in earthen ponds.
Although the rice yield was low, the experimental rice plots provided the features of rice fields in Egypt especially, shallowness and the fluctuation in the temperature regime. As illustrated in Table 2, the Maryout population had poor performance in this system when the average daily gain per fish was 0.28 g/fish/day. This was inspite of its relatively large initial weight. The same strain had the lowest survival rate (81.7%) in comparison to the other three strains which were similar. The Manzala strain had the highest average daily gain (0.45 g/fish/day) followed by Abbassa, then Aswan.
For the growth in enclousers, the hapas used provided crowded environments. Populations seemed to perform differently under this crowded conditions as presented in Table 3. The Maryout population had the highest average daily gain per fish (0.33 g/day) (P<0.05) although its initial weight was the lowest, while the three other strains were similar in performance. There were no significant different in all strains for daily weight gain (DWG),Survival rate (SR) and condition factor (CF).
Assuming that the space does not have any affect on the performance of individual species, average daily gain as g/fish could be the parameter to compare regardless the rate of survival.
From Tables 1 to 4, conclusions can be drawn. The Maryout strain seemed to performing better in pond culture and in under crowded conditions in enclosures but had the poorest performance in the rice fields. The K factor values for the four stocks clearly show that the superiority of Maryout is not a function of survival and/or the space (Tables 1 and 3). On the other hand, the Abbassa strain performed relatively poorly in the enclosure system in spite its large size at initial weight. The remaining observations reflected to a large extent the same rank as the initial weight.
The data in Table 4 illustrate genetic x environment interaction. We may conclude at this point that Maryout strain is expected to perform better under intensive situations such as cages followed by Manzala, while Manzala strain will be recommended for shallow culture systems such as rice fields followed by Abbassa strain. Because of the rank of different strains in pond system was close to the rank of initial weight, the future refining of methodology should minimizing the difference in initial weight to confirm the present results.
ACKNOWLEDGEMENT
This research was supported by International Network for Genetics in Aquaculture (INGA) through a fund from International Development Research Center of Canada (IDRC). Also, to ICLARM Regional Research Center for Africa and West Asia for providing the pond facilities to carry out the research.
References:
Bartholomew W. Green, Esam H. Rizkalla, Ahmed Nassr Alla, Ahmed Khater and Abdel R. El Gamal. 1995. Mass production of Nile tilapia (Oreochromis niloticus) and blue tilapia (O. aureus) fry in relation to water temperature. Pond Dynamics/Aquaculture (CRSP). Thirteen Annual Technical Report.
Eknath, Ambekar E., Melchor M. Tayamen, Marietta S. Palada-de Vera, Jodecel C. Danting, Ruben A. Reyes, Edna E. Dionisio, Josephine B. Capili, Hernando L. Bolivar, Tereso A. Abella, Antonio V. Circa, Hans B. Bentsen, Bjarne Gjerde, Trygve Gjedrem, and Roger S. V. Pullin. 1991. Paper presented at the Forth International Symposium on Genetics in Aquaculture, Wuhan, China, April 29 to May 3, 1991.
El Gamal, A.A. 1997. Egyptian aquaculture: Status and development requirements with special emphasis on tilapias and their potential in aquaculture.In: (Fitzsimmons, K. editor),Proceeding from the Fourth International Symposium on tilapia in Aquaculture,Vol.2,Pages:441-452.
El Sheakh, A, A., A.A. El Gamal and A.S. Diab. 1995. Influences of low water temperature on fat content, phospholipids, neutral lipids and lipases activities in tilapias fish. J. Product. & Dev. 3(1):44-48.
FAO. 1996. Aquaculture status and development requirements. FAO Regional Office for the Near East. Cairo. 45 pages.
General Authority for Fish Resources Development (GAFRD) (1999). Fishery Statistics.
Kamel, E. A. 1999: Genetic studies on Nile tilapia (Oreochromis niloticus) in Egypt. Ph.D. Dissertation, Department of Zoology, Girls College for Arts, Science and Education, Ain Shams University, Cairo, Egypt.
Mahmoud Fouad Esmail Salem. 1997. Effect of some heavy metals on growth performance and chromosomal behaviour of some local tilapia species. Ms. thesis. Tanta University. 69 pages.
Steel, R. G.D. and James H. Torrie: Principles and procedures of statistics, a biometrical approach. R.R.Donnelley and Sons company.
