Tilapia Culture in NEGEV, The Israeli Desert*

Shmuel Rothbard,^1,3 and Yacov Peretz²

¹YAFIT (R&D) Laboratory, Fish Breeding Center, Gan Shmuel 38810, Israel.

²Israel Ministry of Agriculture, Aquaculture Division, Aquaculture Extension Officer.

³Israel Maritime College, Michmoret 40297, Israel.

ABSTRACT

Negev desert, the southern part of Israel, covers more than 50% of the total country area. Since the state of Israeli was established (1948), the governmental authorities have seriously considered that Negev has high potency for future Israeli settlement plans, and extreme importance for settling thousands of immigrants, arriving in Israel after the Holocaust in Europe. The government planned to settle-down small settlements, like kibbutz or collective villages that can be based on sophisticated and intensive agriculture, and clustered around several urban centers. Hydro-geological surveys, initiated soon after the state has been established, have revealed that the Negev and its eastern part, the Arava valley, possess tremendous amounts of saline underground and geothermal waters. Although the water contains variable salt concentrations, it can be utilized for integrated agriculture, e.g. irrigation of agricultural crops combined with intensive aquaculture. At present great parts of Negev have been converted into areas of green agriculture, where fruits and vegetables are successfully grown. In spite of economical constraints, the fishculture industry in Negev has positive tendency of development.

More than 10 super-intensive fish farms have been constructed in various parts of Negev, where the geothermal water is passing through fish culture raceways, and then used for irrigation of crops. The tilapia is one of the most promising species, among other exotic fish (ornamental and edible) species that are presently cultured in Negev aquaculture. In order to achieve fast growing fish, most of the tilapias are either, sex-reversed males derived from crosses between Oreochromis niloticus and O. aureus, or sex-reversed red tilapias. Due to suitable climate and plenty of warm underground water, the tilapias are continuously grown, round-year, to marketable size of 500-700 grams in 6-8 months, in biomass extending the densities of 20-27 kg/m³.

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*pp. 60-65 in: R.D. Guerrero III and R. Guerrero-del Castillo (eds.) Tilapia Farming in the 21st Century

(Proceedings of the International Forum on Tilapia Farming in the 21st Century, Tilapia Forum 2002)

NEGEV, THE ISRAELI DESERT

The Ottoman rulers, followed by the British Mandatory authorities (1918-1948), considered the Israeli Negev desert as an uninhabitable territory whose main importance was strategic and political. They invested only limited efforts in developing the region and improving the standard of living of Bedouins, at that times the only inhabitants of Negev. At present, though the Israeli desert extends over ²/₃ of the country, it is inhabited by less than 10% of the population.

Although the State of Israel borders the Mediterranean Sea, its climate is profoundly affected by the proximity of vast deserts (Sinai and Arabian) to the south and east. Precipitation is limited to the winter season (400 and 800 mm north to Beer-Sheba), which extends essentially from November to March, and declines sharply toward the south and east, dropping almost to zero. Thus, Israel is characterized as semiarid, and the Negev region, which extends over more than 50% of the country, is classed as arid and needs to be irrigated all year round to sustain agriculture (Fig. 1). Even where precipitation is relatively high - in the northern and western parts of Israel - summer crops require irrigation between April and October. Stronger solar radiation, extreme temperatures (Fig. 2) and higher levels of water evaporation from the ground surface characterize the more aridic areas.

Fig. 1. The NEGEV desert, in the southern part of Israel.

Beneath this desert are huge aquifers containing extremely large quantities of fossilized and geothermal water, either fresh or saline. The research detected tremendous amounts of water, stored millions of years ago in an underground reservoir, the largest underground high-quality fresh water lakes existing in Israel. In close neighborhood to these lakes are brackish and geothermic (�40⁰C) waters trapped in separate pockets. These waters cannot be replenished. Hydro-geological surveys have revealed that the Negev and its neighboring Arava valley possess considerable reserves of saline underground water with a variable concentration of salts. For the last 30 years the brackish water has been successfully used for irrigation of agricultural crops (e.g., tomatoes, water-melons, graves, jojoba, olives, etc.). At the beginning of 1970's Israel started investigation of hydrology in the Negev, the arid and the semi-arid part of Israel (Issar et al., 1983). Presence of water in this region has been incorporated into national plans of population distribution and agricultural development. The hydrologists estimate that billions cubic meters of water are stored underground, which can be exploited during hundreds of years, supplying demand of the growing population and agricultural development. From the very inception of modern Israel, settling the desert and turning it into farming land was considered a matter of national priority. First by trial and error and later on followed by research and development, agricultural know-how was incorporated into practice and became a highly useful tool for turning the desert into productive and habitable land.

Fig. 2. Monthly minimum-maximum average temperatures of air and water at EinYahav tilapia farm, during the winter season (ARAVA Valley - NEGEV Desert).

AQUACULTURE IN DESERT

Negev plateau highlands are a district in the Israeli desert with a community of about 5000 inhabitants, which currently use about 4.5-million m³ brackish water per annum, for agriculture-aquaculture purposes. These demand is supplied by means of several wells, at the depth of 550-1000m, equipped with separate pip-lines, supplying brackish-water at the salinity of 2680-4360 TDS and high quality fresh-water (at 39-41¡C)

Fig. 3. A model of multiple and integrated utilization of brackish and geothermal water in Negev.

In the past ten years, investigations have shown the significant potential of the geothermal, brackish water for the successful culture of aquatic organisms (fish, crustaceans, algae, etc.). In order to improve the economic viability of both sectors - aquaculture and agriculture - it is obvious that a chain of users of the desert water is indispensable. A practicable, efficient chain of users is illustrated in Fig. 3.

IsraelÕs semi-arid climate, in which water is a scarce commodity, required the development of an intensive form of aquaculture. In the Negev, brackish water allows its application only for limited agricultural purposes. Therefore, advanced technologies are employed to make maximum use of every cubic meter of water.

Impressive yields have been achieved recently using all-plastic ÔbubbleÕ tanks. Through the entire arid Negev and Arava region, in which air and water temperatures are kept constant throughout the year, yields have been up to 35 times higher than those of fish grown in subtropics in conventional outdoor ponds, and have been achieved in half the growing cycle.

ADVANTAGES OF DESERT AQUACULTURE

Despite the paradoxical context - aquaculture in desert - several clear and significant advantages in development of tilapia aquaculture in Negev desert have been defined at planning:

v Exploitation of brackish water, incompetent for utilization in routine methods of "green" agriculture.

v Polyvinyl cover protection of crops (and fish) grown in greenhouses, allow suitable control of optimal temperature levels, due to high temperatures and intensive solar irradiation, existing in desert, almost all year around.

v Availability of warm geothermal water, which permits optimal temperature levels, during the extreme, although short, cold winter season, existing in the desert.

v Extreme dry climate that facilitates cooling of geothermal water during hot summer, by strong evaporation.

v Abundant low-cost land.

v Presence of high-level human infrastructure.

v Geographic isolation, which facilitates possibility of adequate animal quarantine husbandry.

v Possibility of culturing aquatic organisms without endangering ecological systems or environmental balance.

v Possibility of growing highly priced off-season fish, vegetables and fruits.

v Round year fish production.

THE PROGRESS OF TILAPIA CULTURE METHODS IN NEGEV

Tilapia growth-rates and disease resistance decline at temperatures lower than 20⁰C. Unfortunately; fish farming in Israel faces the problems of low temperatures during five months of the year. In order to keep tilapia alive, development of an over-wintering storage systems become a must. Such systems require relatively high investments in order to support fish with optimal surviving conditions at cold winter. For instance, plastic covered structures have been constructed over fishponds to maintain optimum water temperatures during the course of commercial scale fish growth. Several types of tanks, and methods of polyvinyl coverage have been recently examined: A metal frame greenhouse (with special anti-corrosive treatment of the metal piping), the "Aquabubble" (a frameless inflated plastic cover made of net-reinforced PVC), and other shapes such as the "Igloo" or "Tent" are set up similarly. The cover material selectively blocks infrared radiation escaping from the pond, thus reducing heat loss, while allowing the sun's rays to pass through and warm the pond during the day.

The production strategies used for culturing of tilapia in Negev, have been changed and improved with time.

At the beginning a simple "flow-through" system was used for culturing tilapia. In this system, large volumes of water continually passed through the fish growing compartments, flushing out suspended solids and harmful nitrogenous wastes. Such system was efficient in summer, when the final user (agriculture) needed plenty of fertilizers and water for irrigation of crops. However, at winter, when agricultural demand for water decrease (due to low irrigation levels), excessive amount of water was disadvantageous. As consequence, water recirculation systems were developed, which involved bio-filtration and removal of solid-wastes, to maintain optimal quality of water (reviewed by Avnimelech, 1998). In such systems the daily water exchange rates for fresh as well as for brackish water can vary between 5% and 15%.

In order to maintain optimal oxygen concentration in the super-intensively stocked tilapia ponds, all farms are equipped with mechanical paddle-wheel aerators and/or venturi air-aspirators. The solid and suspended particles in culture tanks are biologically treated by means of aerobic nitrification and flocks of bacteria. Usually such systems are also supported with a trickle-filter, comprised of polystyrene particles or other inert substrates, characterized by large surface, on which nitrifying bacteria form thin films, improving oxidation of ammonia to nitrate. The commercial fish farmers continue to improve the bio-filtration methods. Fluidized beds and trickling filters undergo additional refinements to maintain good water quality.

Fig. 4. Tilapia farms in NEGEV.

With addition to the mentioned above, experimental pilot projects involving hydroponics bio-filtration carried out at the "Desert Aquaculture Research Station", indicate that application of sophisticated filtration methods into the existing bio-filters can largely improve and sustain the quality of water. Such improvement permitted integration of aquaculture and agriculture, ("dual cropping"), whereby herbs and vegetables could become an additional income as by-product of aquaculture.

Skilled personnel and superior management abilities are indispensable prerequisites for production of average annual yield between 20 and 27 kg/m³ of fish. Data collected from four model farms in the Negev and Arava region have shown promising yields and profits. The fish growers, owners of the model farms, who started with total yields of 30-50 tons/annum, decided to expand their production, in order to reach average annual yields of 100-150 tons, with financial assistance of the Israeli Ministry of Agriculture.

Tilapia management in the desert involves all conventional stages known in tilapia culture. Fish are produced either by crossing females Oreochromis niloticus with males O. aureus, or spawning of red tilapia. The fry produced in spawning ponds are sex-reversed by means of male-hormones. Then the fry are nursed in intensive nursing ponds, where they are grown to fingerlings of 5 grams. The fingerlings are transferred to rearing ponds where they reach the size of 80-120 grams. At this size, the tilapias are transferred to fattening ponds, where the fish are grown to the marketable size of 500-700 grams.

Due to suitable climatic conditions and availability of huge reservoirs of underground geothermal water, the fish are continuously round-year produced, which enables permanent and reliable supply of fish supply to the markets.

REFERENCES

Avnimelech, Y. (1998). Minimal discharge from intensive fish ponds. World Aquaculture, 2:32-37.

Issar, A., Oron, G. and Porath, D. (1983). Warm brackish groundwater as a source of supply for integrated projects of root zone warming, aquaculture, irrigation and recreation projects. Pp. 105-115 in: L. Fishelson and Z. Yaron (comp.). Proceedings of International Symposium on Tilapia in Aquaculture. Tel Aviv University, Tel Aviv, Israel. 624 pp.