JOURNAL OF MARINE BIOLOGY
Year:2012 | Volume:4 | Issue:15|Papers Count:12

In this study, investigation was conducted to determine the seasonal species composition and structure of zooplankton population of Caspian Sea at three commercial regions, Amirabad, Nowshar and Anzali harbors in 2010. According to the results a total of 24 species was found to build zooplankton populations. These zooplanktons were include of copepods (4 species), Cladocera (7 species), Rotatoria (9 species), protozoa (2 species) and 2 temporary plankton species (Meroplankton). Maximum species abundance of zooplankton species was recorded in autumn and Winter (21 species) and lowest in summer (15 species). The study showed that the average annual population density and biomass of zooplankton were 3848±1114 /m3 and 35.1±9.6 mg/m3 respectively. Maximum average of annual zooplankton abundance and biomass were belonged to copepods with 3085±810/m3 and 23.9±5.7 mg/m3. Quarterly seasonal review (temporal distribution) of zooplankton abundance and biomass showed that was more in the summer with an average density of 4390±1230 /m3 and 48.9±15.9 mg/m3 in winter, respectively. The aim of this study was to assess the zooplankton population in Anzali, Nowshar and Amirabad harbors which showed the highest density and biomass of zooplankton in Anzali region with 5789±1352 /m3 and 44.7±11.1 mg/m3 respectively and the lowest was in Noshahr with 3142±658/m3 and 32.2±8.0 mg/m3 respectively.

In this investigation effect of fish size on salinity tolerance of two size groups of Caspian sea Zander , Sander lucioperca, fingerlings were investigated. The survival rate and plasma osmotic pressure changes in 0, 6, 24, 72 and 240 h after abrupt transfer to freshwater (0 ppt), 7 ppt and Caspian Sea salinity (12 ppt). Also, Hb, PCV, RBC and MCHC were measured at 240 h. The effect of body weight on plasma osmolarity was significant in both groups. There were not significant changes on plasma osmolarity of both size groups in fresh water. In size group 1, the highest plasma osmolarity value occurred at 72h after transfer to 7 and 12 ppt waters. The same situation was happened in 24 h for size group 2. The plasma osmotic pressure value of both groups reduced in both salinity of 7 and 12 ppt at 240 h and reached to new almost stable status. Hematological parameter values of size group 2 in salinity of 7 and 12 ppt were lower than fresh water at 240 h. Also there was a significant decrease in MCHC value of size group 2 fingerlings after transfer to salinity of 7 ppt at the 240 h. It seems that nevertheless the osmoregulatory mechanisms of size group 2 Zander fingerlings can act better than group 1, but the size group 1 zander fingerlings could tolerate salinity up to 12 ppt during 10 days acclimation period. Therefore we can conclude that zander fingerlings in 1 g body weight can tolerate up to 12 ppt water salinity (Caspian Sea salinity).

One of the important parameter in artificial reproduction of sturgeon is the quality and quantity of male gametes. This study carried out to investigate the quantity of spermatozoa in Persian sturgeon (A. persicus) by determining spermatocrit, counting by hemacitometer and spectrophotometry in 370, 400, 450, 500, 550, 600 and 700 nm wavelengths. The result of morphometric studies in Acipenser  persicus sperm cell was determined. Mean total length of sperm (mm), mean length of sperm tail, mean length of sperm head, mean width of sperm head was 64.69±4.15 (mm), 55.5±4.17 (mm), 9.44±0.48 (mm) and 2.47 ±0.33 (mm) respectively. In this study, the average milt density was 2.047±1.369  109 sperm/ml and spermatocrit percentage was 10.85±6.53%. The results of spectrophotometry showed that the absorption rate decreases due to increase in wavelengths. There was significant correlation between sperm density and absorption rate in all wavelengths. In Persian sturgeon according to correlation coefficient test, 700 nm wavelength shows more correlation compared to other wavelengths. Also, there was no significant difference between spermatocrite percentage and absorption rate and 700 nm wavelength shows more correlation compared to others. The finding shows that there is significant correlation between spermatocrite, density and light absorption in sperm of Persian sturgeon and all of these techniques can used for measuring sperm concentration in Persian sturgeon.

In fish hatcheries, disinfectants are usually used for controlling the infections of body surfaces of the fish and to prevent or eradicate the pathogenic organisms. Copper sulphate (CuSO4, 5H2O) and potassium permanganate (KMnO4) are among the important disinfectants which used in aquaculture facilities. In the present study an attempt was made to determine LC50 in 96 h of these two disinfectants and to study their effects on gills and liver tissues of Acipenser persicus fry in vitro. Persian sturgeon fingerlings with mean weight of 1.57±0.2 mg were maintained in a static system for 96 hours at a water temperature of 23.7±0.38oC, dissolved oxygen concentration of 7.08±0.2 mg/l and a pH of 8.25±0.06. Total hardness of the water was determined as 330 mg/l. Gills and liver tissue of A. persicus fry were examined for microscopic and histopathologcal alterations after 96 h. LC50 in 96 h was determined as 0.15 mg/l and 0.41 mg/l, for CuSO4,5H2O and KMnO4 respectively. Results of histology study showed many lesion including, hyperplasia, secondary lamellae adhesion, thickening of supporting cartilage in gill filaments, elongation of secondary filaments, edema of the lamellae, hyper secretion of mucous in gills, cell atrophy, cell necrosis, cell degeneration of the hepatocytes and intravascular haemolysis in blood vessel of liver. We can conclude that inappropriate use of these disinfectants may result in toxicity of fish and also causes structural changes in fish tissues.

This study was conducted to determine shell selection behavior in five rare hermit crabs in 6 selected stations located in the intertidal zones of Hormuz Island. Seasonal sampling was conducted during the summer 2010 to spring 2011. The samples of hermit crabs from the stations were separately fixed in 70% ethanol and were transported to the laboratory. Hermit crabs were identified with valid key identification at the species level. This identification was verified by comparing the samples with the metatypical hermit crabs samples in the Zoological Museum, University of Tehran. Shells occupied by each of the hermit crabs were identified at the species level. Comparing the samples with the metatypical shells samples in the Conchology Museum, Tokyo University of Science, verified the species. According to our results five hermit crab species (Diogenes planimanus, D. tirmiziae, Coenobita scaevola, Dardanus tinctor and Clibanarius longitarsus) with low abundance were identified in Hormuz Island. These hermit crab species respectively occupied 5, 4, 3, 4, and 2 species of gastropods for protecting their abdominal section. In general, the shell selection behaviors showed that these hermit crabs use the shells of 11 gastropod species and Thais lacera with 19 occurrences (35.8% of all the shells) was the highest frequent occupied shell. Also, the results showed that station 1 (coast of Hormuz Marine Research Center) had the highest abundance of the hermit crabs. 

Many species of Vibrio which is inhibited in warm waters are potentially regarded as food-borne pathogen for human. Aquatic animals and aquatic products can transmit the disease but there is no report about studying the contamination of oysters in Iran. The aim of this research was to study the occurrence of Vibrio species in oysters which caught from the Persian Gulf by using Multiplex PCR methods. In this study for the first time, edible parts of 60 oysters were studied by bacteriologic methods. Standard biochemical tests were done for identification of Vibrio isolates after culture in special mediums. Multiplex-Polymerase chain reaction (PCR) was used to confirm the results. The results showed that 18.3% of the studied samples (11 samples) contain Vibrio and no bacteria were found in 81.7% (49 samples). Among the Vibrio isolates, Vibrio harveyi was the species most frequently detected (10%) and V. parahaemolyticus and V. vulnificus were found in 3.3% and 5% of the samples, respectively. The results indicate that oyster of the Persian Gulf contain Vibrio species which are important for the human health.

In order to evaluating the relationship between osmotic-ionic changes and sexual maturation stages, 30 farmed Acipenser stellatus were selected and were studied for a 1 year period. There was a significant difference in serum osmolarity of males and females at sexual maturation stages in different seasons (P<0.05). Results of ion concentration (sodium, potassium, calcium and magnesium) showed no significance different at early stages (P>0.05), but Ca2+ was decreased significantly (P<0.05) at the stage IV in different seasons with development of sexual maturation and was minimum in spring (8.85±1.49 mEq/L). Concentration of Mg2+ showed a various fluctuation in different seasons with development of sexual maturation and decreased to its minimum concentration in spring (1.66±0.26 mEq/L). In males, besides of Ca2+ and Mg2+, Na+ also showed different fluctuation in different seasons and reached to its minimum concentration in spring (132.66±2.56 mEq/L). According to observed results, there was a direct relationship between osmolarity and sodium ion in males and females. Also, there was a significant difference between calcium ion and sexual maturity development. Therefore it can be concluded that sodium has a major role in osmoregulation and also we give emphasis on calcium ion as major sexual indices in A. stellatus.

In this study the effect of L. acidophillus and its suitable level on survival and growth rate of juvenile Litopenaeus vannamei was investigated during November 2010 to September 2011. L. acidophillus was isolated from shrimp intestine and added to commercial shrimp food. Six formulation diets were prepared by soaking shrimp feed in L. acidophillus solution to achieve 1010, 109, 108, 107 and 106 levels compared with a non-treated diet as control. After 60 days, the shrimp fed diet with 108 bacterial levels, showed a higher mean weight gain (593.45 g) or 170.29% increase in growth rate compared with the control. The mean weight gain showed a decreasing trend as the L. acidophillus level decreased from 108 to 106 and the L. acidophillus level increased from 108 to 1010 in the diets. There was significant difference in weight gain, feed intake, daily growth and feed conversion ratio (FCR) between treated and the control group (P<0.05). There was significant difference between experimental groups and the control in survival rate (P<0.05) but no significant difference in water quality and biochemical composition among treated and control groups (P>0.05). Clearly, treating with L.acidophillus appeared to enhance growth and survival rate of Litopenaeus vannamei. It was concluded that the tested strain may be used as probiotics for Litopenaeus vannamei in aquaculture at a level of 108 L. acidophillus in to the prawn feed.