Iranian Journal of Fisheries Sciences
Volume:2 Issue: 1, Jan 2000

The phylogenetic relationship of five sturgeon species in the South Caspian Sea was investigated using mtDNA molecule. Sequence analysis of mtDNA D-loop region of five sturgeon species [Great sturgeon (Huso huso), Russian sturgeon (Acipenser gueldenstaedtii), Persian sturgeon (Acipenser persicus), Ship sturgeon (Acipenser nudiventris), Stellate sturgeon (Acipenser stellatus)] and DNA sequencing of two Escherichia coli cloned DNA fragments sized 758 bp and 922 bp was carried out. Sequence comparison of the mtDNA D-loop region between the five sturgeon species showed 100 % sequence identity. However comparison between a short (758 bp) and long (922bp) mtDNA D-loop region within Russian sturgeon showed a 5 bp differences. On the contrary a partial sequence of the mtDNA ND5 gene region showed high sequence and organic base variability in the five species. These results indicate that direct sequencing of ND5 gene provide more information for phylogenetic or population level studies in sturgeon species. The present study revealed a distinct classification among the five sturgeon species. On the basis of the phylogeny tree it is clear that a close evolutionary relationship exists between the great sturgeon and ship sturgeon that was verified in five phylogenetic trees. On the other hand a close resemblance was also seen between Persian and Russian sturgeon indicates that these two species have a closer evolutionary relationship. This study also showed a 2.2 % sequence divergence in sequence data for ND5 gene between Persian sturgeon and Russian sturgeon which indicated that these two species diverged from each other approximately one million years ago. However the verification of this calls for DNA sequencing of different genes.

: PCR-based mtDNA analysis (RFLP) was used for the study of population differentiation in the Russian sturgeon (Acipenser gueldenstaedti). The mtDNA ND5/6 gene regions were amplified using PCR techniques followed by RFLP analysis. 39 different composite haplotypes were detected among 62 specimens. 29 haplotypes were rare occuring only once in two regions (west and east areas of the Southern Caspian Sea). The average nucleotide and haplotype diversity within populations were estimated to be 0.0287270.00 and 0.964500042 respectively and divergence between populations to be 0.052%. A highly significant differences were observed in the distribution of haplotypes between the west and east areas.

The study on the ecophysiological impacts of stress in female Persian sturgeon broodfishes revealed that the average cortisol level varried in all broodfish caught at the Sefidrud River (163.3821.2ng mL-1), Sefidrud River estuary (260.2719.7ng mL-1) and Gorganrud River estuary (179.3820.8ng mL-1). The variations in serum glucose levels were 140.6512.05mg dL-1, 144.445.9mg dL-1 and 126.2411mg dL-1, respectively. The maximum level of cortisol (781 ng mL-1) and serum glucose (281 mg dL-1) were observed during the transport of broodfish from the capture stations to the hatcheries and the minimum level of cortisol (25.2 ng mL-1) and serum glucose (33 mg dL-1) were observed during the confinement of broodfishes in the breeding ponds. The rhythmic and significant variations of cortisol level during capture, handling, transport and confinement of female Persian sturgeon broodfish in all three regions can be regarded as a valuable indicator of stress.

: Some haematological variables including Red Blood Cells (RBC), White Blood Cells (WBC) differential counts, Haemoglobin (Hb), Haematorite (HCT), Mean Corpuscular Volume (MCV), Mean Corpuscular Haemoglobin (MCH) and Mean Corpuscular Haemoglobin Concentration (MCHC) were measured in 90 stellate sturgeon juveniles Acipenser stellatus (1-2 years old) and 90 Persian sturgeons Acipenser persicus (1-2 years old) at different water temperature 10-15ºC, 16-20ºC and 21-25ºC. Also these parameters were evaluated in 84 adult including A. persicus (54 samples) and A. stellatus (30 samples) collected from Caspian Sea during spring and autumn 1997. The results have showed that WBC differential counts, Hb, HCT, MCV and MCH were identical for both species at the mentioned water temperatures. However, the values for RBC of A. persicus were generally less than those of A. stellatus. These haematological factors relatively increased with the water temperature increasing. Although RBC and WBC values of A. persicus were less than those of A. stellatus. The rates for HCT, MCV and MCH were higher in A. persicus.

Experimental trials of acclimatization of juvenile Persian sturgeon, Acipenser persicus to different salinites of 0,5,10, 15ppt were studied. The juvenile Persian sturgeons in three weight classes (1.5, 3, 5g) have been transfered from freshwater to different concentrations of saline water. Na, k, Cl- concentrations of blood serum and the changes in the number and size of chloride cells were measured. Na concentration showed an imperceptible trend and K concentration had a decreasing one size of changed chloride cells in different salinities were 8.6-13  0.3 m and their numbers were (25-653) in 5 pairs of fillaments. The results revealed that salinity tolerance was increased with the fish size. According to this study, there is a direct relation between the number and size of chloide cells and salinities and time exposure.

The effects of stocking density of eggs and larvae were studied related to the morphological deformities appearance, percentage of survival, and growth rate, in order to achieve the most suitable stocking density for eggs and larvae in incubators and rearing tanks. The egg stocking densities were 500, 700 and 900 g per incubator for great sturgeon, 500 and 1000g per incubator for Persian sturgeon and 400 and 425g per incubator for stellate sturgeon. Larvae were stocked at densities of 10000, 15000 and 20000 larvae per m3 for great sturgeon, 21660, 41004 and 69000 larvae per m3 for Persian sturgeon and 15770, 23250, 57660 and 62250 larvae per m3for stellate sturgeon.
The results indicate significant differences in percentage of survived in fertilized eggs (P

The present study was conducted to determine the best feeding rates expressed as percent of body weight in Persian sturgeon fingerlings at different body weights. Eighteen fiberglass tanks each holding 30 fingerlings with an average initial body weight of 19.45 ± 0.5 g were used in this experiment. Six different feeding trials (1, 2, 3, 4, 5 and 6 percent of body weight) were employed and each trial was run in three replicates through a period of 60 days (4 periods of 15 days).
The results were analyzed using Statgragh software and compared using Duncan test.
The optimum recommended feeding rate was 4 percent of body weight for an increase of body weight from 19.5 to 31g and 3 percent of body weight for an increase of body weight from 33 to 47g. For an increase in body weight from 47 to 90g the recommended feeding rate was 3 percent of body weight. The recommended doses are subject to alteration with variation in water temperature.