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Evaluation of Growth and Reproductive Performance of Three Strains of Nile Tilapia Oreochromis niloticus Found in Kenya for Use in Aquaculture
New Aquaculture Systems/New Species Research 4 (10NSR4)/Experiment/Kenya
Kenya Fisheries Department, Ministry of Natural Resources, Kenya
Moi University, Kenya
David M. Liti
1) Evaluate the production characteristics of three strains of Oreochromis niloticus.
2) Determine the reproductive efficiency these three strains.
3) Develop a protocol that will facilitate the evaluation of other O. niloticus strains in the future.
4) Train Kenyan biologists in techniques and procedures for species and strain evaluations.
Tilapia have become one of the most abundantly produced fish in aquaculture. They are produced in over 80 countries. The world production was more than 800,000 MT in 1996 (Lovshin, 1997). Of the tilapias, Oreochromis niloticus is the principal species being produced. Its native range includes the Nile drainage from its headwaters in Ethiopia and Kenya to the Nile Delta of Egypt, the Niger drainage, and lakes and stream once historically connected to these drainages.
The cultured stocks of O. niloticus are based on a limited number of collections from the wild, often with a limited number of fish in the founding population. The majority of the world production is based on approximately six initial sources: Ivory Coast, Ghana, Egypt-Manzala, Egypt-Ismailia, Sudan-Nile, and Lake George Uganda. Stocks originating from Aswan, Egypt, and Lake Turkana Kenya are being used in a more limited basis. Many of these introductions were made in the late 1960s and early 70s and have been redistributed throughout the world.
As a result of the small founding populations and the prolific nature of tilapia, many of these populations have become highly inbred, limiting the potential for genetic selection. For example, the 50100 fish of the Ivory Coast strain was introduced into Brazil in 1971. That introduction then became the parent stock for much of the O. niloticus cultured in the Americas. In 1988 Teichert-Coddington and Smitherman found a low realized heritability for fast growth in the Ivory Coast strain and attributed that to a small founder stock and subsequent generations of inbreeding. Hulata et al (1986) found no response to selection for rapid growth using the Ghana strain of O. niloticus. Al-Hafedh (1994) found that 4th generation Egypt strain O. niloticus had promising realized heritability of 0.29 for body weight. Eknath et al. (1993) evaluated four strains recently collected from the wild and four strains with a longer history of domestication and found the three best performing strains were the recently collected ones.
The wide native range of O. niloticus permits the opportunity for genetic diversity with in the species. Agnese et al. (1997) analyzed the genetic differentiation of 17 natural populations of O. niloticus from both the Niger and Nile systems and found there were three basic clusters, West African, Ethiopian Rift Valley and Nile drainage. Within each cluster there were also distinct subpopulations.
Kenya has a unique opportunity as well as a challenge as tilapia aquaculture becomes more established. The country's geography contributes to three unique drainages where O. niloticus is native to one, introduced and well established in another, and present in another where it is not native but beginning to be used in an aquaculture extension program. The Sagana station located in the Tana River drainage where O. niloticus is not native and provides the opportunity to evaluate several strains of O. niloticus without the worry of contamination of indigenous stocks of O. niloticus. The geographical location of the Sagana station offers the potential to evaluate not only those strains which are currently present in the country, but at some point in the future, evaluate other O. niloticus strains found in the upper Nile basin. However, the immediate question is which of the strains currently in Kenya is most appropriate for the rapidly growing aquaculture program, based not only on its culture characteristics but biodiversity considerations as well.
The proposed work plan will help determine which strain of tilapia should be used where as part of a national aquaculture extension effort. Staff will be trained in techniques for evaluating populations of tilapia that can also be applied to other fish species being considered for aquaculture. The potential is to identify more productive strains of O. niloticus that can increase tilapia production worldwide.
Three strains of tilapia currently present in Kenya will be evaluated to determine if any have
unique culture characteristics that favor its use in aquaculture. The stocks to be evaluated will be the
Sagana strain, which is being used in the CRSP, sponsored research and extension efforts in the region, the
Lake Turkana strain and the Lake Victoria strain. The evaluation will consist of three phases,
fingerling evaluation, foodfish evaluation, and reproductive efficiency.
Phase 1: Young fry of each strain will be stocked into small ponds and nursed to 5 g. Growth and
survival will be determined for each pond at the end of the production period. The small fingerlings will
be stocked into 150 m2 earthen ponds at
7/m2 and reared for three months. Ponds will be fertilized
with weekly applications of cow manure and inorganic urea. Growth and survival will be determined at
the end of that period.
Phase 2: Fingerlings of each strain from Phase 1 will be hand sexed and males graded to obtain a
common size for use in a communal culture evaluation. Each strain will be stocked into three replicate
ponds/treatment at a density of 2
fish/m2. All ponds will receive cow manure at 500 kg (dry wt)/ha/wk.
Nine ponds will be managed following a protocol similar to that used in the Kenyan extension program. Cow manure will be added at 500 kg/ha/wk and cassava leaves given daily as a feed at 10% body weight/d. The second set of nine ponds will be managed by adding inorganic fertilizer weekly at 16 kg N and 5 kg P/ha and rice bran given as a feed at 2% body weight/day. All ponds will be sampled every two weeks to determine average weight and seinability of each strain. This phase will be conducted for 5 months after which all ponds will be harvested and growth and survival determined.
In both Phases 1 and 2 the following water quality monitoring program will be conducted: water temperature, dissolved oxygen and pH will be measured weekly in the morning and afternoon at 5, 25, 50, and 75 cm depth. For most analyses, combined water samples encompassing the entire water column will be taken from two walkways extending about 2 m into the pond. Total alkalinity, chlorophyll a, Secchi disk visibility, and total ammonia nitrogen will be measured every two weeks.
Phase 3: Brooders will be stocked into 2
m3 hapas using 8 females and 2 male/hapa and three
hapas/strain. Hapas will be monitored every 5 days and females carrying eggs will be collected from
spawning hapas and transported to the hatchery where they will be allowed to incubate the eggs. Data will
be recorded as to the number of spawns obtained/strain, the number of females that successfully hatch
the eggs, and the number of fry produced/gram body weight of female.
Statistical Design: Null hypothesis: There are no differences in the strains in regard to reproductive success, and growth and survival at different points in the life history. Data will be analyzed by ANOVA to determine if there are differences among strains in the above characteristics.
A protocol for strain evaluation will be developed and tested at Auburn University using the
two domesticated strains commonly cultured and the potentially genetically most unique Kenyan strain,
Lake Turkana strain. This work will be conducted by a Kenyan as part of a Master of Science degree.
The work will be in two parts, genetic analysis and reproductive performance. A production trial will be conducted as part of a future workplan. A genetic profile will be established following the procedures of Agnese et al. (1997) and Liu et al. (1998).
The reproductive performance will be monitored by stocking brooders of two or more strains into individual 2-m3 hapas using 8 females and 2 male/hapa and three hapas/strain. Hapas will be monitored every 5 days and females carrying eggs will be collected from spawning hapas and transported to the hatchery where they will be allowed to incubate the eggs. Data will be recorded as to the number of spawns obtained/strain, the number of females that successfully hatch the eggs, and the number of fry produced/gram body weight of female.
Statistical Design: Null hypothesis: There are no genetic differences in the strains or in their reproductive characteristics. Data will be analyzed by ANOVA to determine if there are differences among strains in the above characteristics.
The proposed work plan will help provide guidelines for evaluation of tilapia strains in the Upper Nile basin. It will help to establish policy regarding fish distribution with in Kenya but also address concerns of other countries in the region. The proposed activities will provide the opportunity for the Kenya CRSP program to provide leadership in the areas of biodiversity and genetic resources.
Data collection: 1 July 2001 to 30 September 2002
Data analysis: 1 November 2002 to 30 April 2003
Final report by 30 April 2003
Al-Hafedh, Y.S., 1994. Estimation of genetic parameters and comparison of breeding strategies for Tilapia nilotica (Oreochromis niloticus), Ph.D. dissertation, University of Guelph, Ontario Canada.
Eknath, A.E., M.M. Tayamen. M.S. Palada-de Vera, J. C. Danting, R.A. Reyes, E.E. Dionisio, J.B. Capili, H.L. Bolivar, T.A. Abella, A.V. Circa, H.B. Bentsen, B. Gjerde, T. Giedrem, and R.S.V. Pullin, 1993. Genetic improvement of farmed tilapias: The growth performance of eight strains of Oreochromis niloticus tested in different farm environments. Aquaculture, 111(1-4):171188.
Hulata G., G.W. Wohlfarth, and A. Halevy, 1986. Mass selection for growth rate in Nile tilapia (Oreochromis niloticus). Aquaculture, 57:14.
Liu, Z., A. Nichols, P. Li, and R.A. Dunham, 1998. Inheritance and usefulness of AFLP markers in channel catfish (Ictalurus punctatus), blue catfish (I. furcatus), and their F1, F2, and backcross hybrids. Molecular and General Genetics. 1998. 258(3):260268.
Lovshin, L.L., 1997. Worldwide tilapia culture. In: Anais do 1 Workshop International de Aquicultura, October 15-17, São Paulo, Brazil, pp. 96166.
Teichert-Coddington, D.R. and R.O. Smitherman, 1998. Lack of response by Tilapia nilotica to mass selection for rapid growth. Transactions of the American Fisheries Society, 117:297300.
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