The reservoir potential for fisheries development in Iran has been considered by a number of authors. Numann (1969) provided data on the Sefid-Rud, Karaj, Latian and Dez reservoirs: El -Zarka (1973) and Clay and El -Zarka (1977) updated the reservoir lists and discussed their potential for fisheries development, basing their estimates on the use of the morphoedaphic index. For reasons beyond his control, the present consultant was unable to up-date the previously published information except for very few reservoirs, and therefore the strategies for stocking large reservoirs are mentioned here only briefly.
Since the Clay and El -Zarka (1977) FAO Mission, fish stocks in some reservoirs have been boosted by stocking of especially Chinese carps. The results of this new strategy, initiated in the mid-1980s, are not well known, as there has been little monitoring of fish catch. Thus, it is difficult to comment on the accuracy of the potential predicted by the above authors, who suggested that 2 027 t/year of fish could be harvested from the 12 major reservoirs of Iran. The present fishery development strategy continues to concentrate on stocking the reservoirs with Chinese and common carp fingerlings produced in hatcheries.
Currently, fish for stocking of Iranian reservoirs are produced in several hatchery/nursery farms, among which figure prominently the Sameshkandeh (Shahid Rajaee) Warmwater Fish Farm in Sari (Mazandaran Province), Jehad Hatchery (Gilan Province), Agricultural Complex Hatchery/Farm (Gilan Province), and the Sad-e-Sangar (Dr. Beheshti) Fish Farm in Rasht (Gilan Province). The following data provided by the Department of Fisheries on the fingerling production show the rapid growth in carp fingerling production in hatcheries: Chinese carps 12 836 163 (1985), 23 070 000 (1986). Of these, the following were stocked into reservoirs: 8 528 000 (1985), 9 605 000 (1986).
Sameshkandeh (Shahid Rajaee) Warmwater Fish Farm was established in 1977. It covers 80 ha, of which 50 ha are under water. In 1986, 8 million fingerlings of predominantly silver carp (95%) were produced, the rest being grass and bighead carps. In 1987 the hatchery produced approximately 55% silver carp, 10% bighead, 25% common carp and 10% grass carp. The number of broodstock kept in this hatchery is approximately: 300 common carp, 95 silver, 6 bighead and 100 grass carp. In 1987, for the last time, broodstock was imported from Hungary. 30% of these fingerlings are released into reservoirs, 70% are supplied to private sector farms. In 1987 14 million were produced, and it is hoped that production of 20 million fingerlings /year will eventually be achieved. This farm is also responsible for reservoir catch statistics, but no data were available during the present visit.
The reservoirs are classified into three categories:
The stocking of selected reservoirs has been going on since 1982, with the following being stocked: Hamoon (Baluchestan Province). Aras (Azarbayejan Province). Minab (Hormozgan Province).
Fingerlings from the farm are transported in plastic bags injected with oxygen in refrigerated trucks (15°C) to reservoirs. The transport may take up to two and a half days, if the fingerlings are destined for distant reservoirs. The stocking takes place during cool months, and it starts earlier in the climatically cooler regions. The stocking density is 500 to 1 000 fingerlings (average weight 2–3 g) per hectare, depending on the estimates of planktonic productivity. In irrigation reservoirs which dry out completely, sections are fenced off with a fine mesh net to prevent entry of pike and pike perch, and then stocked. Experimental fishing has shown that in permanent reservoirs predators form about 5% of the total fish stocks. The reservoirs are usually harvested in 12 to 18 months, but partial harvesting of some large reservoirs may take place already in 6 to 12 months time. Harvesting takes place in cool months as during the hot months few people eat fish. Some smaller irrigation reservoirs may dry out in July and cannot therefore maintain fish stocks throughout the year.
The consultant was informed that fish stock monitoring (catch data collection) in reservoirs is done by the farm personnel. To place the stocking /harvesting management programme on a more sound basis, collection of more data is needed. This would assist in determining the correct stocking densities, serve to adjust fish species composition and help determine the best harvesting size. Such information should cover basic water quality parameters, fish food (algal and invertebrate) availability and quantity, aquatic macrophytes (species, coverage) and their function in the ecology of fish, competition between the stocked and local fish - especially the predators. The last aspect should assist in determining the minimum stocking size of fingerlings needed to minimize their predation by other fish. This should also reduce the number of fingerlings needed for stocking by giving a higher survival rate.
The Jehad Hatchery produces about 10 million of 2–3 g fingerlings of three species of Chinese carp and the common carp. Their fingerlings are stocked into a great diversity of water bodies, including irrigation and other types of impoundments. Usually, little is known of the productivity of such water bodies, and the only indicator is catch. As the practice of stocking such reservoirs using Jehad fingerlings is very recent, there are no data on the success of this stocking. If the stocking is to be placed on a more rational basis, more has to be learned about these water bodies, the stocked fish growth and mortality rates must be established, and catch data carefully collected.
The Agricultural Complex Hatchery/ Farm has 1 200 ha of ponds plus a hatchery, which produces fingerlings of several species of Chinese carp and the common carp. As the farm was closed during the visit of the consultant, no information was obtained on the quantities of fingerlings produced and on the mode of their distribution.
The current rate of stocking into fresh waters of Iran is largely determined by the availability of fry and fingerlings produced in hatcheries. Although the stocking rate in some reservoirs is said to be 500 to 1 000 fingerlings (2–3 g each) per ha, lower stocking rates are applied in larger reservoirs due to the shortage of fingerlings, which as a matter of priority are supplied to fish farms. If the stocking of water bodies other than fish farm ponds is to be placed on a rational basis, a better knowledge of such water bodies is essential. This would make it possible to group them into fish production potential categories. For such classification, it is necessary to have information on a number of parameters as already discussed under the Section 4.3. Regular monitoring of fish stocks, both indigenous and stocked, through careful and systematic collection of statistics on stocking and commercial/ subsistence catch data, supplemented by experimental netting data, when properly analysed, should contribute the information needed for fine tuning of the reservoir fisheries management towards achieving the maximum sustained yield. The constraints and limitations as discussed in Section 4.3 should also be taken into account.
Broadly speaking, reservoirs within the same category should behave similarly, but each reservoir is usually found to keep its individual character which requires a special managerial approach, e.g., through adjustment of stocking rates and harvesting methodologies. A good knowledge of physico-chemical and biological factors, and careful evaluation of management experience should lead to adjustment of stocking rates for an optimal yield and for maximum economy. Although the existing hatcheries are able to produce large quantities of fry, there will always be a shortage of large-sized fingerlings, as their production requires considerable space. The advantage of the large-sized fingerlings is their low mortality after stocking. Knowledge of predatory fish feeding habits in permanent reservoirs will allow one to select a minimum stocking size of fingerlings, which should be slightly larger than that on which the major predators feed.
To assist in better understanding of the fishery potential of a diversity of Iranian inland water bodies, and to improve the technical level of the personnel currently involved in fish production, a proposal is put forward for a training course in inland fisheries development (Annex 3). This course is oriented towards increasing the level of knowledge of Iranian inland waters with fisheries development potential by explaining the physico-chemical and biological background of fish production, and how to use this knowledge for estimating fish stocking rates for various Iranian waters. The course would also provide training in other approaches for increasing inland water fish production, such as extensive aquaculture.
