by
FEBO LUMARE
REPORT ON THE POSSIBILITIES OF DEVELOPEMENT OF SHRIMP CULTURE IN EGYPT WITHIN THE MEDRAP/FAO PROJECT
Although the knowledge on the reproductive biology of Mediterranean Peneids is about 50 years old (Held, 1938), only a few years ago some research aimed to the definition of the basic criteria for the development of a commercial shrimp culture stated (in Spain since 1964–69, in France since 1969, in Italy around 1972, in Portugal in 1972, in Greece around 1975, in Tunisia in 1976, in Israel in 1977), after the first successful trials of shrimp culture in Japan.
Such research line, centred on the autoctonous species P.Kerathurus, stayed for many years on the problems of induced spawning and larval rearing. The first fattening experiemces of P.Kerathurus evidence however the great limits of this species, as if needed about 17 month to reach a good market size (about 30g). This created great problems for wintering, as the animal dies at a temperature of about 6 °C.
Successive studies, carried out with more care, especially in France and Italy, were aimed to the possibility to utilize an alloctonous peneid species, with characteristics that permitted its use at a commercial scale. The choice fell on the Asian Peneid P.japonicus for the following reasons:
- as since the 60ties it is present in the Mediterranean, because it penetrated through the Suez Canal (it is captured along the coasts of most Mediterranean countries, in Egypt it represents about 50% of the total shrimp captures), its introduction did not represent a sort of ecological “pollution”;
- in Japan there was en well established technology for the larval rearing and the fattening of such species, and this knowledge much contributed to the resolution of problems connected to the methodological approach of the Mediterranean shrimp culture;
- it has a high growth rate, as it reached large commercial size (30–35 g) in only 3 months of rearing.
- it has a stonger resistence, compared to the Mediterranean Peneid, to environmental factors (it survives at 1°C), and is stronger in the handling used in rearing;
- for its great affinity in the morphological characteristics with the Mediterranean species, its commercialisation did not created any problems, especially on the European markets.
The great problem for the commercial development of shrimp culture was however the absence of the species in the wild, especially along the central-south Mediterranean; new studies on the artificicl reproduction of P.japonicus in captivity were therefore needed.
The problem was solved in these last years according to two methodologies. One emphatizes the role of photoperiod on the sexual maturity in captivity, but this method is not very efficient in a large scale, if the aim is to produce high number of post-larvae (around some millions). The other method, that uses the eye stalk ablation, associated to some changes in the environmental parameters, permits to exercise, more than an induction a real control on the reproduction. It enables to synchronise the egg deposition and to manage the post-larvae production on a commercial base (from 10 million onwards). Recently the optimisation of autosufficient artificial food for post-larvae (Pl-45) further improved the sector, also in terms of management economy.
The resolution in economical terms of the problems connected to massive fry production, permitted to activate, in these last years, a series of studies on the fattening of P.japonicus. The first approch on such theme took as model the consolidated Japanese technology of intensive rearing. These techniques, even if of real interest in the Japanese economy, which can pay very high prices for shrimps (80–150.000 Lit/kg), can only partially be tranferred in the Mediterranean economy, for two reasons: a) intensive rearing requires expensive artificial food (about 15,000 Lit/kg), which at a mean conversion rate of 3, costs about Lit 40.000/kg of shrimp reared, with a final production cost of about the double of the normal price in most European and Mediterranean markets; b) large size (from 30–35 g is preferred to small size (18–25 g) which can be obtained in intensive rearing.
After some research on intensive rearing in more or less complexe structures (double bottoms, water recycling, etc..), such considerations led us to follow some models of development of the shrimp culture more suitable to the European and Mediterranean environmental reality (availabily of wide surfaces) and to the market needs. In these last years two types of shrimp culture are now being developed, the economicity of which has been demonstrated. A fist type concerns the sewn of postlarvae p22 for restocking purposes in brackish lagoons characterized by a low natural production. Some research carried out for some years showed that where natural fish production reaches 35–50kg/ha year, it is possible to obtain captures of P.japonicus varying from 17 to 42%, with a cost-benefit value from 1:4 to 1:8. Where the predation pressure is very high (150–200 kg/ha/year of natural fish production), the percentage of capture of the Peneid is generally low (1–5%) and it is not advisable to sow.
The other direction of the shrimp culture concerns the extensive rearing in monoculture, in earth ponds with organic and inorganic manuring of the waters. Such method, which requires low power consumptions (0.1–2% water exchange per day) permits to produce 200–350 kg/ha of shrimps (35 g) in 3–4 months, with large profit margins. Such trend in shrimp culture is at present the most suited to the European and Mediterranean regions, as it produces large size animals with highly remunerative production costs. It is also charachterizes by low technology that permits a easy introduction also in developing countries. This productive system which approached the one carried out in the South-East Asia and Central America, can certainly be improved through the integration of artificial and/or natural food (fish processing by-products, etc.,) permitting more interesting yields (600–1.000 kg/ha/4–5 months), the present studies are aimed in such direction to reach a more profitable form of semiintensive P.japonicus rearing.
Within the MEDRAP/FAO activities, a mission was carried out on some areas of the Egyptian Mediterranean coast, from 6th to 11th May 1985, to study the possibility of insertion of a pilot plant for shrimp production. This program is included in a wider plan of aquaculture development in Egypt. In this country, the possibility of development of shrimp culture seems to have a great economical interest, for the following reasons: a) wide brackish surfaces available, b) high market price of shrimp (in the wild, P.kerathurus are caught in a percentage of 50%, P.japonicus in 49%, P.semisulcatus in 1%) which varies from 15 to 30 L.E., compared to 1–6 L.E. of the more expensive fish species (SParus aurata, Dicentrarchus labrax et Mugil cephalus); c) very favourable climatic situation, such to permit to hypothise two harvests per year.
Among the various area visited (Raswa and Damietta on the Manzala Lagoon near Port Said and some areas of the Maryut Lagoon near Alaxandria), the most interesting one is Raswa, where there is a fish, farm (Raswa farm belong to the Goevernment, it covers a surface of about 500 ha) with emptiable ponds, of suitable shape and size to promote shrimp culture activities.
For such area, we can propose an experimental plan for shrimp culture articulated in the following way:
The P.japonicus fry could be furnished, free of charge except for travel expenses, by the Italian National Council for Research. The only problem of this program if represented by the low salinity which, in the entry of the plant is about 10%o (value indicated as minimum) in some periods of the year (corrisponding to winter, after rainfalls), even if normally values of over 13–16%o are reported.
Even if there are some experiences of keeping P.japonicus post larvae at salinities of about 20%o, it would be useful to carry out a rearing trial on P.japonicus in hypohaline waters at the FAO Training Centre in Policoro, Italy. Such experiment, which is due to start in June 1985, will use three 1.000 m2 earth ponds, to be sown at a density of 1 50 m2. The salinities will regulated to 5%o, 10%o and 37%o, after a short period of acclimatation (48hours) of the post larvae.
The general planning of the management and of the collection of data on the shrimp ponds in the Training Centre will be uniformed to the scheme proposed for Raswa Farm in the Manzala Lagoon.
The importance of such enquiery is the fact that, if the results are positive, we take into account the possibility of a double production cycle, 4–5 months each (March–July, August–November), such hypotheses could be checked in Raswa farm in a second year of experiments; in a third year, some trails could be carried out on the semi-intensive rearing (fertilization × food integration, final production aim 500–800 kg/ha), with two productive cycles per year.
The developement of a shrimp culture along the Egyptian Mediterranean coasts necessitates the realisation of suitable structures for the fry production at large scale (around tens of millions at medium term). Such phase of the production requires two moments, one for the brood stock availability, the other for the rearing of larvae and post-larvae. As far as the first aspect is concerned, we can think at 3 main reference models:
The realisation of the structure for the sexual maturation of females and for larval rearing up to postlarval P22 size requires some foundamental conditions:
To summarize, we can assert that at present there are on the Egyptian Mediterranean coasts some very favourable conditions for the development of shrimp culture:
All these elements let us hope for a quick and important development of shrimp culture in Egypt.
