H. Abdolhay, H. Bradaran Tahori
Excerpts:
In the Caspian Sea more than 123 species and subspecies of fish are found (Kazanhef, 1992), of which five sturgeon A. persicus, A. gueldenstadti, A. nudiventris, A. stellatus, and H. huso.
The fingerling production of Iran Fisheries Company are A. persicus (88.1%), A. gueldenstadti (5.4%), H. huso (2.7%), A. stellatus (2.5%), A. nudiventris (1.3%), resp. in 1996.
The first Iranian hatchery operation was constructed by Russian experts in 1971 (size: 72 ha pond). The number of fingerlings produced was 1.6 and 5.8 million in 1972 and 1973, resp.
The fingerling production decreased between 1981 and 1986 (less than 2 million). The reason was the production of Chinese carp, the decline of broodstock and the overfishing of sturgeon in the south of the Caspian Sea. The Iranian Fisheries Company increased the area of fingerling production. The fingerling production in Siahcal started in 1988 with 134 ha ponds, the Shahid Marjani farm also started for sturgeon in 1988 with 30 ha and Shahid Rajai farm started with 40 ha in 1995. Another farm of 144 ha ponds is Woshmgear farm started in 1996 with 90 ha ponds and will be ready this year with a total of 144 ha.
Hatchery techniques in Iran:
The season of sturgeon breeding and fingerling production is restricted to the period from March to July for the hatcheries of the south of the Caspian Sea. Hatchery facilities are used at least twice during the breeding and rearing seasons. Most beluga (H. huso) are caught in winter time and the broodstock is kept up to the suitable time for spawning. The beluga migrate to Sefidrud river in early spring. Persian sturgeon and sevrjuga are spawning in late spring and their fingerlings are stocked in May. The other species such as A. stellatus and A. nudiventris migrate to Sefidrud, Tajen, and Gorganrud rivers.
Broodstock are often selected from fisheries stations around the rivers by experienced hatchery staff. Large numbers of animals have to be captured and examined to obtain sufficient numbers of mature fishes that will spawn within a few months of captivity. They are checked by sampling of eggs and control of the GV and if they are not suitable for injection they will return to the fisheries station for processing of caviar.
Sturgeon pituitary glands are used for induction of ovulation and spermiation. Glands are obtained from the commercial sturgeon catch and are stored after dehydration in acetone. Recently also LRH-a synthetic analogues were used to spawn sturgeon. The dose of pituitary and LRH-a injection depends on temperature and species. The collected eggs will be fertilized with semen which is diluted with hatchery water to avoid polyspermia.
The most popular egg incubator in Iran is the Yuschenko's trough which is designed by Russian experts. Recently Iranian experts, trained in Russia, constructed a new incubator system (Asoter).
Fingerlings are produced in tanks with live food up to or beyond metamorphosis, followed by grow-out in pond.
This method is suitable for Iran because of the low production of larvae to overcome the problems associated with the possible high mortality of larvae in the ponds. Between 15000 - 20000 larvae are stocked in each round tank (2 * 0.5 m). Fry is fed white worms, zooplankton (Daphnia) and brine shrimp (Artemia urmiana). After reaching 70 - 80 mg body weight, fry are stocked in fertilized ponds to complete grow out. The survival rate in tanks, incubator and ponds is shown in table 1.
Most ponds have a surface of 1-2 ha. The stocking density is between 70000 - 90000 per ha, which depends on species and fertility of the pond. Stocking density can be increased by using aeration, up to 200000 larvae per ha. The survival rate increased from 50 - 60% to 85 - 90% and the average fingerling production increased from 50000 to 100000 per ha. The average body weight of fingerling at release is about 3 g.
Table 2 shows the sturgeon production (meat and caviar) in Iran. Broodstock is selected from rivers and commercial stations (near the river) and transported to the hatcheries. All fish are slaughtered after spawning. Juvenile fish are released into river deltas or upper estuaries.
The capture fisheries of sturgeon has changed because of increasing fingerling production of A. persicus (table 3).
Sturgeon ranching is considered as highly profitable aquaculture venture by Iran. The value of caviar however is at least 100 times that of flesh and caviar product is the greatest contributor of profit in sturgeon ranching venture.
Table 1: Fingerling production in Iranian farms in 1996
(figures refer to the 3 species A. persicus, A. stellatus, H. huso, resp.)
Broodstock capture (No): 644 - 236 - 17
Injected broodstock (No): 381 - 165 - 10
Spawning rate (%): 86.1 - 54 - 83.3
Total fecundity (No): 256,946 - 138,091 - 240,458
Relative fecundity (%): 7882.7 - 9574 - 2766
Fertilization rate (%): 67.6 - 44.4 - 45
Survival rate in incubator (%): 63.1 - 32.1 - 38.7
Survival rate in veniro (%): 72.1 - 72.6 - 74.7
Stocking density (No/ha): 82,860 - 99,833 - 72,941
Survival rate in pond (%): 58.2 - 54 - 55.6
Fingerling production (No): 10,779,938 - 316,214 - 346,300
(No = number of animals)
Table 2: Total sturgeon production (meat and caviar) in Iran
Production (ton): 1861.2 (year 81-82) - 1659 (82-83) - 1738.3 (83-84) - 1865.3 (84-85) - 2046.9 (85-86) - 1836.1 (86-87) - 2022.4 (87-88) - 2002.9 (88-89) - 2052.7 (89-90) - 2072.9 (90-91) - 1900.7 (91-92) - 1315.9 (92-93) - 1251.8 (93-94) - 1120.2 (94-95)
Table 3: Composition of capture fisheries in sturgeon
(A. persicus, A. gueldenstadti, A. nudiventris, resp.)
1972: 4.2% - 89.6% - 6.2%
1988: 44.2% - 50.2% - 5.6%
1991: 57% - 40% - 3%
1994: 69% - 27% - 4%
Conclusions:
In Iran and the few other sturgeon ranching countries the time from the initial stocking of fingerlings to fishery return is 10 - 20 years longer than in other aquaculture venture known. All commercial fishery for sturgeon in the sea proper has been banned since the 1960's and only Iran catches fish in river deltas by gillnet.
IFC increased fingerling production from 5.9 million in 1994 to more than 20 million in 1997. It is possible to develope fingerling production because of good knowledge, availability of ponds and support of the Iranian government for investment, but cooperation between five countries is necessary to provide rules and regulations for sustainable harvesting fisheries.
(correspondence from Iran Fisheries Company (Shilat), No 45 Mahan Alley, Vesal Shiraz Ave., Teheran, 14168 Iran)