No abstract

Samples were taken in March 1999 at the Aquaculture Center of S. Marjani, southeastern part of the Caspian Sea, Iran. Juveniles were raised for 18 months to sizes ranging between 1,500 g and 2,100 g (mean weight 1,850 g ± 129, n = 60; total length range = 60.4 to 71.6 cm (mean 66.1 ± 2.58, n = 60). Fish were raised in circular fiberglass ponds. After a growing period of over one year, experimentals may have been unintentionally exposed to contaminated feed and were subsequently fed with the presumed infected feed batch for fifteen days. Some changes in swimming behavior, feed uptake, and an overall weakness were observed in the test series similar to what has been identified in the cultured fish. Clinical investigations included hemorrhagy in the head, abdominal placoids and curvature of spinal column as well as yellow spots in the pectoral areas. Therefore, a clinical study was initiated and the aflatoxicosis syndrome was recognized by clinical observations when fish were exposed to contaminated food. Aflatoxicosis caused 8.6 percent mortality, while during a period of 40 days the fish lost 7 percent of weight (AGR = -3.2). Huso huso regained weight after 75 days when feeding the fish with an uncontaminated commercial feed.

The performance of two sturgeon hatcheries handling brood stocks were scored during the spawning season in [2002][2003]. The brood fish were caught from the southern part of the Caspian Sea. In total 158 mature adults were propagated at the S. Rajaei fish farm and 269 at the S. Marjani farms.After checking the developmental stages and egg quality of the females and after hormonal injections of fish, eggs were removed and fertilized by hatchery methods commonly used for acipenserids (Billard, 2000). Incubation temperature ranged between 17 and 22ºC and the incubation period lasted 5to 7 days.About 55 percent of the breeders responded positively to hypophysis injections. The range of numbers of germinal vesicles (GV) of spawned fish varied from 4.4 to 9.9 in the S. Rajaei farm and from 4.7 to 11 in the S. Marjani farm. In immature breeders the value was more than 11. The optimum temperature for spawning ranged from 15.5°C to 18°C and 17-20ºC in S. Rajaei and S. Marjani farms, respectively. The average weights of the breeders were 28.1 kg in S. Rajaei farm and 30.3 kg in S. Marjani farm. The average fork length, GV and fertilization rate that are important performance factors in breeding of acipenserid fish were 170 cm, 7.6 and 75.3% in the Rajaei farm, 159 cm, 7.9 and 64.5% in the Marjani farm, respectively. The performance as identified by these fctors was considered to be significantly different between the two hatcheries (P<0.05).