An investigation on the sturgeon stocks in southern Caspian Sea

We launched a summer and winter cruise using two fishing vessels to assess the stocks of the sturgeon fish in the southern coasts of the Caspian Sea in the year 2004-2005. Eighty five random stations were selected and sampled using a 9 meter trawl in waters less than 10 meters and a 24.7 meter trawl for the depths above 10 meters. We caught 170 sturgeons in the summer cruise which comprised 142 Acipenser persicus, 19 Acipenser stellatus, 4 Huso huso, 3 Acipenser nudiventris and 2 Acipenser guldenstadtti. In the winter cruise, 118 sturgeons were caught of which 75 were A. persicus, 41 were A. stellatus, 1 was A. nudiventris and 1 was A. guldenstadtti. Catch per unit effort (CPUE) was calculated as 2 fish for summer cruise with the A. persicus being the most abundant species with 1.67 individuals per trawling while for A. stellatus this was 0.22. For H. huso, the CPUE was 0.05 and for A. nudiventris it was 0.04. For winter cruise, the CPUE was calculated as 1.38 fish, again with the A. persicus as the most abundant with 0.88, while that of the A. stellatus was 0.48. The CPUE for A. guldenstadtti and A. nudiventris was 0.01 in the winter cruise

Poređenje gustine nasda nereis diversicolor u prirodnim i uzgojnim (anzali lagona) uslovima

Nereis diversicolor is regarded as a live food and is significantly effective in increasing stocks, enhancing tolerance in sturgeons and also increasing survival of sturgeon fry. Research conducted indicates that N. diversicolor is more abundant in May as compared to other months of the year. In February, only breeders of this species are found in the environment. N. diversicolor was found in four different weight classes from March 2009 to February 2010. They showed decrease in density with increase in temperature and reached the lowest numbers in February. In years 2009 and 2010, 200 sampling conducted monthly at the point where Caspian Sea mixes with the Anzali lagoon. Sampling was performed by Van Veen sampler with 400 cm2 cross section. Sediments were washed through a sieve with 0.5 mm mesh size. The residue along with Nereis was transferred to a dish, worms separated and transferred to lab. The density of worms per m2 was calculated according to the density formula. Two experiments were conducted to determine the best stocking density for the culture of N. diversicolor. Stocking density of 381-6350 worms m-2 were used in 6 trials initially and best growth was recorded in trial with density of 381 worms m-2. In the second experiment using 381-3175 worms m-2 in 7 trials, trial with 381 worms m-2 again showed better growth as compared to other trials. These results obtained were almost similar to those obtained for N. diversicolor is in its natural environment (447 worms m-2)

Feeding habits of sturgeon fishes in shallow coastal waters of Guilan Province, southern Caspian Sea

We collected sturgeon specimens from seven fishing stations operating 30 to 35 Km away from each other in Guilan province over the years 1999 MD 2000. Trawl nets six meters long were drawn using motorboats at each station, repeated three times for each season. Among the studied premature sturgeons, 121 Acipenser persicus specimens with an average age of less than two years and a length of 10 to 49.9 ± 0.77 cm showed full stomachs (57.17 % fullness). Among the mature specimens with an average age of 11 years and a length range of 90 to 194 cm, only three showed full stomachs (11.54 % fullness). The highest gut index in this study belonged to premature A. persicus. A one-way analysis of variance showed no significant difference in condition factor and gastro-somatic index among the different length groups (P<0.05). We found that the food consumed by premature A. persicus was comprised of eight genera of benthic invertebrates Hypania sp., Hypaniola sp., Pterocuma sp., Stenocuma sp., Abra ovata, Paramysis sp., Gammarus sp. and Nereis sp. Adult sturgeons were found feeding mainly on fish species belonging to Gobidae, Atherinidae and Clupeidae families. The main preys of premature A. persicus were polychaet worms Hypania sp. and Hypaniola sp. belonging to the class Sedantaria. Crustaceans Stenocuma sp. and Pterocuma sp. of the class Cumacea were also seen in the diet of the premature sturgeons. The main preys of adult A. persicus were fishes belonging to the family Gobiidae and secondary prey were fishes of the family Atherinidae

The effects of temperature, salinity and photoperiod on sexual maturity and concomitant reproduction behavior in Nereis diversicolor

Nereis diversicolor worms were collected from the Anzali lagoon during the years 2004-2006 using Van Veen grab sampler with a surface area of 400cm ^(2). Water salinity, temperature and total organic matter (TOM) of sediments in the sampling region was determined. The worms were maintained in 0.5 tons (1x1m ^(2)) tanks until they reached a weight of 200-300mg. Sexual maturity in the samples was attained at 4-6C and spawning occurred at approximately 16°C. The first gametes were observed after the temperature increased from 6 to 16C. Sexual maturity was studied at various salinities (0.5, 5, 12, and 15 ppt). Results indicated that the worm attains sexual maturity at salinity 15ppt in a shorter period as compared to other salinities. No significant differences were observed between sexual maturity attained at salinities 12 and 15ppt (P>0.05). The effect of light and photoperiod in synchronizing reproduction in male and female N. diversicolor was also studied. We observed that reproduction behavior in adult worms increased for a period of one week at the end of each month after they were exposed to a prolonged photoperiod (L:D 16:8) followed by a period of dim light. Mature males crawled around outside the tubes in search of a female. In the presence of a mature female, the males released sperm directly in front of the female tube. Soon after, there was an increase in the activity of the females which showed intense ventilation movements. The female worms with their eggs already released began to carry the sperm into their tube. The ripe females nearby which had not yet laid eggs in their tubes released their gametes a few minutes after the male and began to carry sperm into their tubes. The fertilized eggs remained inside the tube protected by the female. The benthic larvae developed fast, feeding on the mucus and microbial film on the tube wall. After 10 to 14 days, larvae began to leave the tube. A few days later the females died

Efekat tri različite hrane na rast i preživljavanje larvi persijske jesetre (acipenser persicus)

A feeding experiment was conducted to evaluate growth and survival of Persian sturgeon larvae fed with live food (Nereis diversicolor and Daphnia spp.) and artificial diet. Diets were included: Diet 1: Dafnia (Dafnia magna), Diet 2: Nereis diversicolor worm; Diet 3: Mix of Daphnia (Daphnia spp.) (50%) and Nereis diversicolor (50%), Diet 4: Mix of Nereis diversicolor (50%) and concentrate food (50%) and Nereis diversicolor (50%); Diet 5: Mix of Daphnia spp. (33.33%) and Nereis diversicolor (33.33%) and concentrate food (33.33%). Persian sturgeon larvae were distinctly transferred to 15 tanks and fed for 15 days. For each treatment, 60 larvae were stocked into tanks. The total length and body weight of the fish were determined once before initiation of the experiment and at the end of the experimental period to assess their growth performance. Water quality parameters were recorded two times a day. There was significant difference (P0.05) were not found between diets 2 and 3 and also between diets 4 and 5. The value for BWI, PBWI, GR, DGI, SGR was higher in larvae fed mix of Nereis diversicolor and Daphnia spp. (diet 3) (p<0.05) and there was significant difference between all of groups. Except diet 3 there was no significant difference in the CF of fish fed the survey diets

Summer and winter feeding behavior in Acipenser persicus and Acipenser stellatus in the south Caspian Sea

Feeding behavior in Acipenser persicus and Acipenser stellatus in summer and winter was studied from 2004 to 2006 simultaneously with the marine survey for sturgeon stock assessment. Bottom trawls (9m) on board the research vessel Sisara 2 (50 hsp) were used to collect specimens at depth below 10m, while specimens at depths more than 10m were collected using bottom trawls (24.7m) on board the Guilan Research Vessel (1000 hsp). Examination of stomach contents of 135 A. persicus and 80 A. stellatus specimens revealed that the food spectrum was composed of bony fishes (Neogobius sp., Atherina sp., Clupeonella cultriventris), invertebrates belonging to the family Ampharitidae (polychaeta worms including Hypanai sp. and Nereis diversicolor), various crustaceans (Gammarus sp. and Paramysis sp.) and the bivalved mollusc, (Abra ovate). Significant differences were detected in the frequency of prey items in the different seasons studied. Also significant differences (P<0.05)

Study of possibility of reproduction and mass culture of Nereis diversicolor

The present study was firstly conducted to study the rate of sexual maturity in Nereis diversicolor under suitable conditions of temperature and photoperiod. The second objective was to determine the potential of artificial breeding in these worms for mass culture. Nereis diversicolor worms were collected from the Anzali lagoon in 4000 sampling operations during the year’s 2004 to 2006 using Ekman grab with a surface area of 400 cm2. The water salinity, temperature and total organic matter (TOM) of sediments in the sampling region was recorded. The worms were maintained in 0.5 tons (1 x 1 m^2) tanks containing clayey-muddy sediment to a height of 20 cm covered with 10 cm water (5 ‰) until they reached a weight of 200-300 mg. Sexual maturity in this species was attained at 4-6 ºC and spawning occurred at approximately 16 ºC. The first gametes were observed five weeks after the temperature increased from 6 to 16 ºC. Sexual maturity was studied at various salinities (0.5, 5, 12, and 15 ‰). Results indicate that these worms attained earlier sexual maturity at salinity of 15 ‰, compared to other salinities studied. No significant differences (P>0.05) were observed between sexual maturity attained at 12 ‰ and 15 ‰. Stocking density (20, 50, 100, 150 worms) was studied in terms of sex and showed that number of females were higher than males and the ratio was 11:1 (female: male). No significant differences (P>0.05) were observed between the various stocking densities and their replicates. The effect of light and photoperiod in synchronizing reproduction in male and female N. diversicolor was studied. It was evident that reproduction behavior in adult worms increased for a period of one week at the end of each month after they are exposed to a prolonged photoperiod (L:D=16:8) followed by a period of dim light (simulated using 1 W lamps). Feeding trials were carried out with Saccharomyces cerevisiae, formulated fish diets and humus. Results showed that this diet was effective in speeding up sexual maturity in worms and significant effect of treatment was observed (P<0.05) in worms fed a diet of humus alone. Eggs and sperms were fertilized and worms developed from the young monotrochophore with jelly layer to the trochophore larvae

Stock assessment of sturgeon fishes in the southern part of Caspian Sea (Iranian water)

The marine survey for sturgeon stock assessment was conducted in summer, winter and spring in the years 2006 and 2009 to estimate the relative and absolute abundance and percentage composition of each species in the Guilan, Mazandaran and Golestan Provinces. This survey was carried out in the Iranian waters of the Caspian Sea on board the Sisara2 and Guilan vessels using trawl nets at 2-100 m depths. Trawling was carried out in 85 stations that were selected using a stratified random design. The number of stations in each scope was based on the area of the scope in terms of the total area. Trawling and sampling in shallow water up to 10 m were carried out using 9 m trawl nets whereas 24.7 m trawl nets were used for depths more than 10 m. Trawl surveys were carried out in the daytime. Trawling velocity was kept at 2.5-3 kts and trawls lasted half an hour in order to calculate abundance, and biomass of sturgeons using the swept area method. Catch per unit area (CPUA) in the winter 2006 survey was 3853 specimens nm^2 , in the summer and winter 2007 survey was 1854 , 2912 specimens nm^2 at depths less than 10 m respectively . CPUA for sturgeons in spring 2008 survey was 2103 specimens nm2 at depths less than 10 m and 393 specimens nm2 at depths greater than 10 m (10-100 m depth). These values in the winter 2008 survey dropped to 44 specimens nm^2 at depths at depths above 10 m. CPUA for sturgeons in the spring 2009 survey was 300 specimens nm^2 at depths less than 10 m and 307 specimens nm^2 at depths greater than 10 m. In all the surveys conducted CPUA for A. persicus was higher than that for the other sturgeon species. Based on the calculations carried out in the marine survey in winter 2006 the estimated absolute abundance for sturgeons was about 2977.363 thousand. The total biomass of sturgeon was estimated as 131.713 tons. In the summer 2007 survey total abundance was estimated 1432.398 thousand, and total biomass of sturgeons was estimated at about 312.161 tons. In the winter 2007 survey total abundance for sturgeons was estimated at about 2250.105 thousand, and total biomass was estimated 578.08 tons. In the spring 2008 survey total abundance was estimated at about 3002.832 thousand. The total biomass was estimated at about 2533.318 tons .In the winter 2008 survey total abundance was estimated at about 152.722 thousand, and total biomass in winter 2008 was estimated 170.540 tons. Total abundance in spring 2009 survey was 1310.232 thousand and total biomass was estimated at 2019.tons. Investigation of stomach content of sturgeon Acipenser persicus caught under 10m depth in 2006 to 2007 surveys showed that there is significant difference in the consumed food. Polychaeta is the major food consumed and crustacean an the minor one(P>0.05).Also no new types of food( such as bony fishes or benthic) have been observed in food chain of Acipenser persicus only the food consumption rate has been related to the season of year and increases or decreases in warm or cold seasons, respectively For physiological study and determination of sexual maturation stages in sturgeon,119 gonad sampling prepared. The results showed that 63 % of fishes were females and 37 % of them were males. Gill microscopic study shows complications such as hyperplasia, curvature, adhesion, embowed, shorting and lengthen of secondary filaments and fraught bloody. Microscopic study on liver indicates signs of cloudy inflammation, fatty degeneration, dispersion of billed secretions and cell atrophy. The population genetic structure of Persian sturgeon (Acipenser persicus) in Sefidrood and Gorganrood rivers watershed analyzed based on microsatellite markers during sturgeons assessment in 2006-2008. Results showed that Acipenser persicus in two region of south part of Caspian Sea are two independent populations