4. EXPERIMENTAL STUDIES

4.1 CONDITION OF BREEDERS

Kept over-crowded in small cement tanks and maintained on artificial feed, the breeders were not only in poor condition, but were also of low fecundity. In both sexes, even by the middle of the breeding season, only about 50 percent of the stock were in acceptable condition to be considered for spawning. The weight of ovaries in such specimens ranged from 10 to 60 g in total weight and the number of ova/kg body weight from 70 000 to 90 000. The breeders did not spawn readily when introduced into Dubisch ponds. Those that spawned did so in two to five days; many did not spawn at all. By transferring these fish to manured, natural ponds having gentle flow of water and feeding them regularly, the condition of both males and females improved and they were spawned later in the season.

Among the two-year-olds, some of the males were mature and oozing milt and could be used for spawning. The two-year-old females had not matured.

4.2 CARP SPAWNING BY DUBISCH METHOD

One pond at Wadi Yabis was utilized for this purpose. Three female breeders and five males were introduced into the pond. Owing to heavy seepage, water flow was continuous. The fish spawned on the second day after introduction. Fertilization and hatching were good, but survival was very poor even though regular artificial feeding with finely powdered feed was given. Tadpoles abounded in the pond and at the end of two months only 1 700 fingerlings were obtained.

At Sukhneh, in Mr. Hamdan Dabaj's fishery, in one Dubisch pond, five females and seven males were introduced, and though there was repeated spawning in which all the females participated, the number of fingerlings that could be obtained from the pond was only 650.

Heavy seepage of water from the ponds, very poor plankton production and excessive competition for food from tadpoles were factors responsible for poor survival of spawn.

4.3 EGG COLLECTORS

Twigs of fine-leafed plants were planted in a Dubisch pond in which spawners were released. The fish spawned profusely on the egg collectors which were removed carefully and re-planted in another pond for hatching. Though the hatching was good and large numbers of spawn could be seen in the pond during the first two days after hatching, their survival was very poor, realizing only about 970 fingerlings out of approximately 100 000 spawn. Factors restricting survival of spawn in the Dubisch pond operated in this pond as well.

Egg collectors or kakabans made of split palm leaves and kept submerged in Dubisch ponds were freely utilized by breeders for spawning. Transferring these kakabans to cloth enclosures for hatching yielded better results than in ponds and by this method production of spawn and fry could be increased as compared to the Dubisch method (see Section 4.6).

4.4 SPAWNING AND HATCHING ENCLOSURES

Cloth (nylon) enclosures, 2 × 1 × 1 m, floated by means of a four-piece wooden frame and held in position by means of four metal rods, each 1.1 m long, were found very convenient to spawn selected speciments of carp in any body of water. Submerged aquatic weeds, split palm leaf kakabans and kakabans made of casuarina (Casuarina sp) twigs were tried in these enclosures. Heavy spawning occurred with aquatic weeds and with palm leaf kakabans, which could easily be removed and kept in floating, open cloth enclosures for hatching. Over 120 000 spawn per fish were obtained by this method. The technique of spawn taking from these enclosures was repeatedly demonstrated. Two or three days after hatching, when the yolk is practically absorbed and the spawn are moving actively and normally, they are carefully transferred to prepared nurseries for rearing (see Sections 4.7 and 4.8).

4.5 HYPOPHYSATION

In order to increase seed production and stagger the same over a longer period during the year, carp breeders refusing to spawn in the presence of egg collectors alone, were administered intramuscular injections of fish pituitary gland hormones and were successfully induced to spawn. Various aspects of the technique of hypophysation, including collection, preservation and storage of pituitary glands, extraction of hormones, selection of spawners, preparation of injection dosages and administration of intramuscular injections were repeatedly demonstrated to a stage when counterpart personnel could carry out the work independently. Minimum equipment required for this work has been assembled locally.

Collection of pituitary glands from local species of fishes such as Barbus sp (local name - Gishre) and Clarias sp (local name - Balbooth) - both of which are of cultural importance, was also demonstrated.

Gravid, female specimens of Clarias sp, ovulated about 12 h after the second injection, but in the absence of ripe males, eggs could not be fertilized. Ripe females were available in the swamp at Azraq during August.

During April-May freely oozing males of Barbus sp were common in Azraq and they measured 195 mm or over. Females were generally larger in size, but no mature specimens could be found. That the fish successfully breeds in the Azraq swamp was indicated from the fact that fry and even post-larvae of various size were available in the swamp during May-June.

4.6 SPAWN PRODUCTION AND SPAWN TAKING

As already stated, it was repeatedly demonstrated that by introducing egg collectors in the spawning pond and removing these, after spawning, to enclosed, floating hatcheries, production of spawn could be appreciably increased. Use of spawning enclosures, in which spawners and kakabans or weeds are introduced together, prevented loss of eggs while spawning, and thinning out and distributing the weeds or kakabans into a series of hatcheries, a much larger percentage of fertilized eggs hatched out into spawn. The eight females that spawned in Dubisch ponds at Wadi Yabis and at Sukhneh had the capacity to spawn over 2 million eggs and even though all of them spawned, the total number of fingerlings that could be obtained out of these was only less than 3 500. On the other hand, four females, with a spawning capacity of about 1 million eggs, were induced to spawn in spawning enclosures and, by hatching the eggs in floating hatcheries, over 306 000 spawn could be obtained. The number of spawn obtained per female spawner ranged from 60 000 to 112 000. Excluding the spawn produced in the Dubisch ponds, a total quantity of 330 000 spawn (4–5 d old after fertilization and 2–3 d after hatching) were obtained by adopting the use of spawning and hatching enclosures.

Methods of careful handling of eggs while distributing in hatcheries, removal of spawn from hatchery enclosures, separation of spawn from weeds and debris, enumeration of spawn by sampling and bulk measurements when large quantities are to be quickly handled were repeatedly demonstrated for the benefit of the local staff.

4.7 NURSERY PREPARATION

Spawning/hatchery ponds constructed at Wadi Yabis and Sukhneh were subject to heavy seepage, and heavy manuring with cattle dung, oil cake and superphosphate, followed by inoculation with zooplankton (cladocerans), collected from natural rain water accumulations, did not have the desired effect on plankton production. As the water in the pond was being practically renewed every day by seepage, the spawn at commencement of feeding did not get any natural food in these ponds. Generally on the day of hatching and the day after, an appreciable number of spawn would be found in the pond, but thereafter very few could be seen, indicating that at this critical stage, when they start taking food from outside, the majority perish due to lack of natural food. Artificial feeding with finely powdered feed did not materially alter the situation, though the few surviving fry grew well. Seven ponds of this category utilized for spawn rearing gave the following results in a period of six to eight weeks:

At Azraq, a partially excavated, small, shallow nursery pond, holding about 25–30 cm depth of water, was manured with cattle dung and oil cake and the water was inoculated by pumping in some water from the neighbouring pond which had some copepods and a thin algal bloom; 20 000 spawn from Sukhneh were transported in a plastic bag and stocked in this nursery and 50 g of artificial feed powder were broadcast all over the pond daily. In spite of low water level, survival of spawn appeared very good, three days after stocking. However, when the ecosystem was disturbed by pumping in water every 3–4 d, the number of fry seen in the pond appeared to decrease. In spite of this, over 5 000 fry are expected to be harvested from this nursery.

4.8 CEMENT CISTERN AS NURSERY

Two cement tanks, each 21 m² in area, belonging to Mr. Hamdan Dabaj at Sukhneh, were prepared for spawn rearing as follows:

After dewatering and cleaning, a 7–10 cm-thick layer of garden soil was spread at the bottom of tank 1, while the second was left without bottom soil. The tanks were then filled to a depth of 1 m and manured as follows:

Both tanks were inoculated with live zooplankton and given a supplementary dose of manure, 24 h later, as follows:

Four days after the above manuring, when plankton weredeveloping in tank 2 and fairly good in tank 1, they were stocked as follows:

Artificial food in the form of fine powder was given daily at the rate of 30 g/day for the first five days and thereafter at 50 g/day. Water level in the ponds was gradually raised by about 5 cm every day. Particulars of fry and fingerlings harvested are as follows:

In tank 1, plankton at the time of stocking was good and increasing and that was the main reason for the excellent rate of survival. In tank 2 the plankton were not adequately developed at the time of stocking and a number of early fingerlings of local species of fishes had gained entry into the tank unnoticed. Against these unfavourable conditions, a survival rate of 35 percent in 25 days is considered quite satisfactory. Because of the relatively lower survival, the growth of fry was much better than in tank 1.

The above experiments clearly demonstrate the importance of stagnant water ponds and abundance of natural food for satisfactory survival of carp spawn.

When a third cistern was heavily manured and inoculated, plankton production was extremely high, but the swarms of plankters depleted the oxygen in the water. Spawn released in this tank were largely confined to the upper layers of water and after about 15 days there was large-scale mortality of fry. Excessive crops of plankton can, however, be periodically harvested with a tow-net and utilized for feeding spawn in neighbouring ponds.

Local species of fish take a heavy toll of carp spawn. A cement tank in Hajee Hussai's fishery was manured and about 15 000 spawn were stocked in it. The majority of the spawn, however, were preyed upon by the large number of local fish which had earlier entered the tank and had not been removed. Only a few hundred spawn survived and these naturally grew rapidly.

4.9 FRY AND FINGERLING PRODUCTION

Total production of fry and fingerlings during this season, up to end August 1972, was as follows:

Production could be increased appreciably over the previous years only by rearing spawn in cement tanks as detailed above.

More breeders could be induced to spawn, even up to mid-October, by administering pituitary hormone injections and further crops of spawn reared to further increase seed production during this season.

4.10 PILOT EXPERIMENTAL PONDS

One of the larger ponds at Wadi Yabis was cleared of weeds and an attempt was made to fill it up with water. Seepage, however, was extremely heavy and, even after six days' continuous supply of water, it was not possible to maintain water in the pond. As has already been recommended (FAO/TA 2448, p. 11–12), it is not considered advisable to conduct any further attempts at improving these ponds, as such attempts would be very costly.

At Azraq/Shishan, a plot about half way between the village and the swamp was selected for construction of pilot experimental ponds and an area of approximately 0.7 ha of water surface area was excavated by bulldozer into four ponds, one of 1 000 m² and two others, each of 3 000 m². A small nursery pond of approximately 30 m² area was also excavated nearby. An earthen dam was put up across the Baker-Harza canal; water level in the canal was thereby raised and it was then diverted through a narrow canal to the ponds. Wire net screens were fixed at the mouth of the canal and also at the entrance to the ponds, so as to prevent entry of unwanted fish.

By the end of June, pond 1 was filled up to a depth of 1.2 and daily observations on the rate of seepage/evaporation were initiated. Temperature of water in the pond was recorded daily in the morning and in the afternoon. It was observed that when the water level in the pond exceeded 90 cm level the seepage/evaporation loss per 24 h was 1–2 cm. An appreciable extent of lateral seepage was observed. There was also some seepage into the newly excavated neighbouring ponds which had not then been filled. When the water level came down to 90-85 cm there was practically no seepage loss and whatever loss that was recorded (1 cm in two or three days was perhaps only due to evaporation. Mudalla (1968) estimated the rate of evaporation per year at Azraq at 2 m, which works out to about 0.55 cm/day. This shows that if the pond had been excavated a little deeper, over 1 m depth of water could be maintained in the ponds without seepage loss. The markedly clayey soil at the bottom also indicates that seepage will be minimal in these ponds. Water temperature in pond 1 during July-August ranged from 22 to 27°C.

4.11 MANURING, STOCKING AND PRODUCTION

With the water level at 1.12 m the pond was manured during the first week of July as follows:

Besides an unknown stock of Tilapia sp (including 15 to 20 mm fry) that entered the pond through the water supply, 1 000 fingerlings of carp, 39 to 85 mm long, average length 63 mm, and average weight 6.5 g, were stocked on 6 July 1972. Ten carp fingerlings, 100 to 130 mm/25 to 50 g (average 120 mm/40 g) were also introduced along with the above stock.

Fifteen days after, a further dose of manure was applied as follows:

The water turned light green and copepods and cladocerans were common in net hauls of plankton. One month after stocking the fish were sampled with a small meshed cast net with the following results:

Considering the larger specimen of carp fingerling as the average for that group, there has been an average increase in weight of 32 g in 30 days. In the case of the smaller fingerlings the increase in weight during the period is about 200 percent over the initial weight at stocking. On the basis of the number of carp and tilapia caught in the sampling net it is estimated that the stock of the latter species in the pond is at least 300. The total increase in weight of the entire stock of carp and tilapia in the pond during the month reaches the level of about 200 kg/dunam/year, which is quite satisfactory for a newly constructed pond.

Intensive breeding of tilapia, had, in the meantime, started in the pond and several broods of fry were observed.

The stock in the pond was put on limited artificial feeding for the next 15 days and just 1 kg of soybean oil cake was given as the daily ration. Sampling on the sixteenth day gave the following results:

During the fortnight the total increase in weight of the entire stock of fish (including about 10 000 tilapia fry) in the pond amounted to about 17 kg, which exceeds the production level of 3 000 kg/ha/year. The approximate average increase in length and weight recorded for the fortnight are as follows:

The water conditions in the three ponds and the natural spring on 26 August 1972 were as follows (expressed as ppm):

Though these short-term observations cannot form the basis for conclusions on production on annual basis, they are indicative of the satisfactory response of the water to management measures such as manuring and feeding. The fact that both carp and tilapia grow well and remain healthy (the latter breeds also) in the new pond, coupled with the observation that seepage loss is minimal, would seem to warrant the inference that, if properly stocked and managed, these ponds will give very satisfactory production. The water conditions in the manured pond are suitable for growth of fish. The spring water is rich in nutrients like phosphates and nitrates. The salinity of the spring water is comparatively low, though in the stagnant ponds the salinity is higher, owing to the influence of the saline soil in the area. The level of salinity however does not seem to affect growth of carp and tilapia, and with the spring water perennially available to replenish evaporation loss, the salinity is not likely to exceed the present levels very much.

4.12 COMMERCIAL FISH FARM

Even the preliminary observations recorded in the foregoing paragraphs indicate that water and soil conditions at Azraq are suitable for construction of fish ponds aimed at commercial production of fish. Owing to geographical contours and the nature of the soil, the Azraq spring waters cannot be utilized for extensive agricultural operations. However, the present observations indicate that these waters can be fully utilized for commercial production of fish in large natural ponds.

According to Mudallal (1968) the annual water flow of Shishan springs are of the order of 1 200 m³/h or 10.5 million m³/year. Considering the rate of evaporation and seepage, the flow from even one of the eyes of the main Shishan spring would be more than adequate for maintaining a large commercial fish farm of at least 50 ha of water surface area.

The swamp in which the Baker-Harza canal terminates is the lowest lying area in the region and this can be easily reclaimed into large fish ponds. A possible layout of ponds in such a fish farm is indicated in Fig.1.

4.13 ARTIFICIAL FEED

In order to exploit the spring flows for intensive cultivation of carp in running water, a cheap artificial food is essential. A feed formulation developed in 1966 and in use at present costs about US $ 210.00/t and has approximately 28 percent crude protein content. The cost of this feed remains high as some of its components are imported into the country.

A detailed study of different types of feed components presently available in the country and their nutrient value in terms of crude protein and fat content was made and, aiming at a relatively high percentage of protein and comparatively low cost, the following formulation has been suggested for trial:

Including expenditure on mixing and pelleting the cost of a ton of the above feed will not exceed US $ 80.00. The crude protein content in the above feed will be about 24 percent. Experiments on acceptability and conversion ratio of the feed have been planned to be carried out at Azraq and at Wadi Yabis.

4.14 IRRIGATION RESERVOIRS

A very preliminary study of the irrigation reservoirs Ziglab, Shueib and Kafrein showed that all three are comparatively deep, with limited marginal shallow areas, devoid of aquatic macrovegetation, with very clear water having very little plankton and with very few fish. Though Ziglab was stocked with carp and tilapia as early as in 1966, there is no evidence that carp has established itself in the reservoir, even though there are reports that carp weighing 4 kg have been caught by anglers from the reservoir. Local species of tilapia breed in the reservoir, but they do not appear to have multiplied rapidly, probably because of the relatively poor food resources in the water. Specimens of tilapia, 6–8 cm long examined from the reservoir did not appear too healthy or fat. A specimen of Labeo (?), 19 cm long, caught from Ziglab in April, was oozing milt freely. In Kafreing an Shueib, even local species of fish are very few.

The catchment areas of these reservoirs are sparsely cultivated and consequently enrichment of these waters by nutrients in precipitation run-off is extremely limited.

The relatively small size of these reservoirs will make them more amenable to management measures as in the case of ponds, for development of fisheries. However, the indigenous species of fish locally available do not appear to be adequate for fully exploiting the ecosystem.

4.15 MARINE AQUACULTURE

In the Gulf of Aqaba, Jordan has a coastline of about 24 km up to the newly adjusted border with Saudi Arabia. A brief survey of this coast line was made to examine possibilities of fish culture in salt water.

The entire coast line is rocky in nature and there are no suitable areas for economic construction of natural fish ponds. The tidal range is about 1 m and the intertidal zone is narrow. In shallow marginal areas seaweed abounds on rocks. Several species of variously coloured coral fishes, several species of perches and parrot fishes are common in the Gulf. During May-June, young ones of several species of perches, 20 to 40 mm long, were common in the area. A more detailed study of the occurrence and abundance of fish seed in the area during different months alone will indicate if even aquacultural practices in floating enclosures would be feasible there.