Khuzestan Province has about 65 000 km2 covered by water, which includes marshes and swamps. This represents about one third of the total water surface area of Iran. The province is rich in rivers, the upper reaches of which are suitable for cold-water fishery, while the lower ones harbour warm-water fish. The present total fish yield from fresh water is not known. There are two major capture fisheries, i.e. that for semi-migratory fish (e.g.Barbus) in rivers and marshes, and that for a mix of species in reservoirs. Concerning aquaculture, Khuzestan has at present about 1 000 ha of production ponds, all of them private. These produce mostly silver and bighead carps, and some grass carp and common carp. At present, Khuzestan receives almost all fry and fingerlings for stocking from Esfahan, Mazandaran and Gilan provinces, as there is only one functioning hatchery in the province itself. Most seed comes from Sad-e-Sangar and Sameskandar hatcheries. A new hatchery/farm is under construction about 25 km southwest of Ahvaz on the right bank of the Karun River. When completed in about 4 years time, it should cover 200 ha, and have production capacity of 100 million fry/fingerlings of Chinese carp per year. The water for the pond system will be pumped from the Karun River. A new inland water research institute is to be constructed in the same area and will use part of the farm for its experimental work and pilot studies. These should include investigations on fry and fingerling production of Barbus grypus and B. Sharpeyi, two economically important semi -migratory fish of the southern Iran (see below).
Some information is available on water quality of the River Karun and on reservoirs of the Karun and Dez Rivers (Table 6). The Dez River is a right-hand tributary of the Karun. The Daz dam was completed in 1964, resulting in formation of a reservoir with a maximum water surface area of 63 km2, as compared to 340 km2 surface area of the Karun River reservoir which was formed approximately 10 years later. Both reservoirs have similar water chemistry, with a relatively high dissolved salt content as indicated by their conductivity. The pH and the conductivity of the Karun are higher than those of the Dez. The concentration of dissolved salts increases downstream from the dams. The Karun River water chemistry in its lower course, i.e., in the area of the future hatchery and research institute, is still suitable for fish culture.
There are two major marshes in this province. One, situated southwest of Susangerd, extends into Iraq and is fed by the Karkheh and Tigris rivers. The other - Shadegan marsh - is situated south and southwest of Ahvaz, and is fed mainly by the Karun River. Shadegan marsh reaches the Tigr is River in the southwest, and in the south it borders the Persian Gulf. Both marshes are well known as wintering sites for numerous migratory birds. The area of Shadegan marsh is dominated by Typha dominguensis and Scirpus sp. This marsh was studied in 1978 by Abbasi who provided the following list of fish: Barbus sharpeyi, B. grypus, Aspius vorax, Chalcalburnus cadimacula, Mugil abu, Ilisha sp., Sparus cuvieri, Silurus (2 species), Barbus cuteus, Glyptothorax sp., Barbus sp. According to Abbasi, the marsh has a maximum depth of 50 cm, maximum water temperature of 30°C, high alkalinity and hardness (figures not available). Barbus sharpeyi, an omnivorous cyprinid, is the most common species; it is followed by Barbus grypus which feeds on macrophytes. Barbus grypus breeds in marshes, and Shadegan marsh is the major source of this fish. In Iraq, B. grypus is the most important commercial fish, and in early 1970s it accounted for 23% of the total fish production (Al-Hakim et al., 1981). It is found in all Iraqi waters, and in 1970s it dominated the fish yield in Dukan reservoir. Welcomme (personal communication) provides a market survey for Iraq capture fishery for the year 1976, giving the following dominant species: B. sharpeyi - 4 243 t, B. xanthopterus 2543 t, Silurus triostegus - 691 t, B. grypus - 519 t. Welcome visited three major fish culture stations, i.e. Zaarafanyia, Latifiya and Riyadh. In 1977 the Zaarafanyia station produced 5 million fry, mainly B. xanthopterus, B. sharpeyi and B. grypus. In the Turkish Euphrates of the same river catchment system, the riverine Barbus esocinus is now a common fish in a large reservoir constructed on this river (Ozdemir, 1987). Although not reported from Iran (Coad ?1981), it appears to have good potential as a reservoir fish and could probably be introduced from Turkey.
Barbus sharpeyi reproduces at the end of the winter (February) in the clean water of rivers with sandy bottoms, at a temperature of 15–16°C. This species is also known from rivers of the Khorramabad areas in the mountainous Lurestan province. There is interest in enhancing the stocks of these local fish species. In the Dez and Karun rivers, Barbus kersin is another popular species, which is known to reach up to 100 kg weight. Liza abu is a mullet frequenting the same rivers. In Lake Assad, a reservoir on the River Euphrates in Syria, Liza abu and Barbus Kersin are among the four (the other two being Varicorhinus trutta and Silurus triostegus) most important commercial fish species (Kolbing and Seifert 1981) and are probably also suitable for Iranian waters, especially reservoirs.
A considerable system of irrigation canals is present throughout Iran but little is known about its use for fishery. It can be said, however, that in common with other countries in the region, Iranian canals are very little used as a medium for fish.
Dez-Karkheh connection is a relatively wide canal which carries water from the Dez to Karkheh when there is a need for irrigation water. The normal rate of flow through the canal is 6 m3/s, and the maximum is 20 m3/s. However, for most of the year the canal is stagnant as there is no irrigation demand. This water body is thus available for some part of the year for fish production. While stocking and harvesting of this canal should not constitute a problem, there are some obstacles to be overcome. During stagnation periods the canal probably develops a relatively high primary production which could sustain fish feeding on planktonic algae. The longer the retention of the water in the canal, the higher the fish yield which could be achieved. A sudden release of water would wash away the accumulated algae and introduce river water poor in organic algal production. This would produce an unfavourable environment for fish. Even if there were barriers in the form of nets or bars to prevent the fish from being washed by the current from the canal into the Karkheh River, they would grow only slowly in the river water entering the canal. One management measure could be the removal of the fish from the canal to another place, perhaps a pond constructed a alongside the canal, where the fish would remain for the required period. By providing feed, the fish could be maintained at high densities, which would reduce the size of pond required. Soon after the canal became stagnant again, the fish could be transferred back. Various stocking rates of a mix of species and their growth rates under different rates of water flow could be investigated in a pilot study in fenced off sections of canals.
Another pilot study, using a similar design, could be undertaken on oxbow lakes. Such oxbow lakes, or temporarily stagnant sections of a river which stops flowing during some months, would require a similar managerial approach if used for fish production. Some of these oxbows and rivers are used for water transfer in the same way as the Dez-Karkheh water canal.
A fifteen Kilometer long stretch of Salman canal, circumventing Ahvaz, is also available for fish production. This is a wide canal, which periodically carries water from the Karun River to marshes in Iraq. Occasionally, the water release through this canal triggers a massive migration of Barbus, and on one occasion not long ago, 100 t of this fish were harvested within a few days. It was not possible to obtain the name of the species so one can only guess the type of migration which took place. It could have been Barbus grypus, which migrates into reed marshes to breed, or B. sharpeyi, which migrates from marshes upstream to breed in clear water of streams. The information provided indicated that strong migratory movements are not a regular annual feature, but take place only once every several years. Stocking of fish in Salman canal would face similar problems as stocking oxbows or canals used for limited periods of time for rapid transfer of a large volume of water, i.e., how to prevent the escape of fish, and how to provide sufficient food for fish during the time when river water of low nutritional value is passing through the canal. The use of intensive or semi-intensive culture in cages could also be experimented with, if fish feed were available.
Doroudzan reservoir on the Kor River, which has its catchment in the Zagroz mountains, provides storage for a system of irrigation canals and water supply for Shiraz. The discharged water temperature is around 13°C throughout the year as the water uptake for irrigation is situated 25 m below the high supply water level. Two cubic meters per second are currently taken from this discharge for the Marvdasht coldwater trout farm near the dam. This farm, established in 1985, at present concentrates on growing fingerlings from eyed eggs purchased from Denmark. It has some broad stock, and it has also started to produce a marketable size trout. The Marvdasht farm, which belongs to Martyrs Foundation, is presently managed by Shilat. The farm consists of an indoor hatchery and outdoor facilities, with large plastic tanks for growing the smallest fingerlings, and rows of raceways of different sizes. As its water uptake from the irrigation system is limited to 2 m3/s, further expansion of the farm is planned to involve the use of the river water for fish ponds to be constructed on river banks.
Downstream of the farm, water in the lined trunk canal gradually warms up to about 16–19°C (in the summer). This water is potentially available for non-abstractive use, such as for raceway fish farming. Techniques and experience for this type is, however, not yet available, and in this respect the situation is the same as in a number of other countries in the region, which have irrigation water systems. The canals downstream of Doroudzan reservoir contain water between March and the end of September. The Ministry of Power, which owns the canals, has offered their use for fishery purposes.
Doroudzan reservoir, about 100 km from Shiraz, has surface area of 58 km2 and is situated at l 676.5 m a.s.l. According to Clay and El-Zarka (1977) the reservoir was thoroughly studied by the Inland Fishery Research Institute at Bandar Anzali. A report produced by Emady in 1977 mentioned two stockings of the reservoir with trout fry 400 000 in 1970 and 2 million in 1972. In 1974, 300 000 rainbow trout imported from Australia were added, and in 1984 and 1985 a further 100 000 each year, supplied by the Kelardasht farm. Experimental fishing in 1976 gave very poor trout return. Bullock and Rolande (1971) suggested that the poor survival of trout in reservoirs with Varicorhinus (two species are present in Doroudzan reservoir, i.e. V. aculeatus and V. bushei) may be due to their competition for space. Another possibility is that trout was decimated by heavy poaching during its migration into the inflowing river. At present, no rainbow trout are captured, but earlier the dam management staff occassionally captured one by rod. During 1985 and 1986 due to drought, the reservoir water level was extremely low, and this could have also had a negative impact on the trout population. During my visit in July, the surface water temperature was about 27°C, and at such temperatures the trout would be expected to descend to deeper water layers. However, deep-water experimental fishing carried out in previous years did not yield any trout either. Trout could also have migrated into the inflowing river and died or been captured there. The lack of monitoring from which one would be able to better judge the fate of the introduced trout fingerlings, makes any suggestions on future introductions difficult. At present it would appear that Doroudzan reservoir is unsuitable for rainbow trout and that any attempts to re-stock this fish again should be abandoned. Effective monitoring and analysis of data are essential for developing correct stocking strategies for reservoirs and lakes.
In 1976 ?Rutilus was stocked and is now well established. The consultant did not see the fish, and therefore its taxonomic status could not be confirmed. It is possible that in some way this fish has competed with trout, perhaps for food. The stocked ?Rutilus grows to a maximum length of about 20 cm, but this size is considered to be too small for this fish to become popular as food. If the reservoir is to be developed for fisheries, this should be preceded by a sound knowledge of the present fish stocks. Such surveys should be conducted by the Fisheries Department, and apart from concentrating on the fish stocks of the reservoir, a study of fish migrations into the inflowing river should also be undertaken. The current fishing pressure should be evaluated, both in the reservoir and in the river. Among other aspects to be scrutinized, are the impacts of: settlements upstream from the reservoir on water quality of the river; water uptake for irrigation ; the agricultural use of pesticides; the discharge of pollutants into the river, etc. Two trout farms are known to exist upstream of Doroudzan reservoir and their impact on water quality should also be assessed.
About 60 km west of Shiraz, at an altitude of some 2 000 m a.s.l., there are seven lakes (Haff Barm) in a hilly area devoid of trees. The catchment is largely used by pastoralists and small areas are under cultivation.
Only three of the seven lakes contain water permanently. The estimated water surface area of these round lakes is between 25 and 100 ha and the lakes differ in aquatic plant cover. While one lake is almost completely covered by Phragmites, Typha, and Scirpus, and has rich meadows of the submersed and floating plants Ceratophyllum, Myriophyllum, Polygonum and Potamogeton, another lake (the smallest one) is virtually free of emergent plants, with only patchy distribution of some submersed plants. The third lake, circled by emergents, appears to be free of aquatic plants in its center. This lake is also the largest and deepest one (max. depth of 6 m). The lakes are an environmentally protected area, for which a warden, living on the shore of one of them, is responsible. The first lake (and probably also the third one) was stocked with pike perch in 1977, while 150 000 common carp and grass carp were stocked in 1984. Gambusia is also present. Experimental fishing carried out before the visit of the consultant resulted in catch of the two local species of Varicorhinus and the stocked common carp, but no grass carp. It is possible that the stocked fry was eaten up by pike perch although there is no evidence to substantiate this assumption.
Angling in these lakes is allowed, and the number of licences and catch are registered with the Office of Environment and Conservation, which is in charge of this protected area.
Over the last several years, the aquatic vegetation, especially the emergent Typha and Phragmites, has become denser, gradually encroaching on the open areas. This might be the result of a temporary climatic change, with less precipitation, which would have lowered the water level or it could also be a result of an accelerated input of soil from the catchment as a result of intensified pastoralism and plant cultivation. Another possibility could be an increased input of organic material leading to eutrophication of the lakes. Perhaps it is a combination of all three factors; however, without having detailed observations little can be said to confirm these suggestions.
A biological method of controlling the submersed weeds by grass carp would seem appropriate. However, the experience with the total loss of stocked fry/fingerlings shows, that larger fingerlings need to be stocked to secure high survival rate by preventing predation of the stocked fish by predatory fish and by birds. As hatcheries in the area do not have facilities for growing large grass carp fingerlings, a pilot approach in using small sized pens directly in these round lakes might be applied to produce the right size of fingerlings for their later release. This should protect fish fry from both fish and bird predations. Such experiments should be approved by the Office of Environment and Conservation responsible for these lakes. The consultant was informed that this Office has already gained some experience from weed control in Lake Parishan, situated some 260 km from Shiraz. This lake, an important bird wintering area, is protected. The management activities on this lake apparently include aquatic weed control using a mechanical weed cutter owned by the Conservation Unit. The cutter could probably also be used on other water bodies facing a weed problem, although because of its large size the self-propelled cutter would be destructive on small water bodies such as the above described round lakes. On these, an integrated approach using a combination of small-scale mechanical cutting, a herbicide harmless to aquatic organisms, and subsequent stocking with grass carp would probably be the best approach for controlling the aquatic weeds.
