JOURNAL OF MARINE SCIENCES AND TECHNOLOGY
Year:2009 | Volume:8 | Issue:1-2|Papers Count:9

This study was carried out to investigate the specific activity of amylase, protease and lipase, as a selective criterion of probiotics, in some Bacillus sp. and Lactobacillus sp. isolated from intestinal tract of yellowfin seabream, Acanthopagrus latus. The results showed that all seven Bacillus and three Lactobacillus isolates were able to produce enzymes, although the specific enzyme activity was significantly different between the isolates. The specific activity of enzymes was higher in Bacillus isolates than in Lactobacillus isolates. Maximum and minimum activity of protease was observed in Bacillus BP5 isolates (3.13 IU/mg protein) and Lactobacillus LP1 isolate (1.03 IU/mg protein) respectively (P<0.05). Highest and lowest amylase activity was observed in Bacillus BP6 (3.00 IU/mg protein) and Lactobacillus LP2 (0.04IU/mg protein) respectively. Bacillus BP6 (1.40 IU/mg protein) had maximum lipase activity and was significantly different from other isolates (P<0.05).

An eight week feeding trial was conducted to determine the energy requirement of growth in yellowfin sea bream (Acanthopagrus latus) fed with diet containing three energy levels (20, 22 and 24 kj g-1 crude) and wet diet (Trash fish). Triplicate groups of 20 fish (12±2.1 initial weights) were each stocked in 300-L fiberglass tanks and fed twice a day to apparent satiation. Survival rate and body weight gain (BWG) were independent of the dietary treatments. Formulated diet and wet diet significantly affected condition factor (K) and food conversion ratio (FCR). K increased with the increase of energy from 20 to 24 kJ gr-1 but FCR decreased with increasing energy levels. Viscera somatic index (VSI), hepatosomatic index and intraperitoneal fat ratio (IPF) were highest in formulated diet. Moisture and ash contents decreased with increasing energy levels in diet, but carcass lipid content, gross energy retention (GER), protein retention (PR) increased with increasing dietary energy. GER was significantly affected by diets with high energy (24 and 22 kJ/gr diet) or low energy (20 Kj/gr and wet diet) contents. The liver droplet area (LDA) was the highest in fish fed high energy diet. The results indicated that the optimum dietary energy levels and the best P/E, for the best growth performance of juvenile yellow fin sea bream were 21.9 kJ in gr. diet 25 g kJ-1, respectively.

Effect of different levels of dietary nucleotide was studied on growth indices and proximate analysis of common carp with average weight 7.54±0.2 during 8 weeks. This experiment was carried out in 300 L circular tanks with 20 fish per tank at the Aquaculture unit, School of Natural Resources, TMU. Dietary nucleotide was added to the diet at a rate of 0, 0.2, 0.3, and 0.4 percent. Fish were fed 5 times daily at a rate of 4-7% body weight. After 56 days of feeding, results showed that dietary supplementation of nucleotide had significant effect on condition factor (P<0.05), but not on final weight, feed conversion ratio, weight gain, and survival (P>0.05). Analysis of proximate composition showed no significant differences in ash, moisture, and protein content (P>0.05). The highest fat content was observed in fish fed 0.2% nucleotide (P<0.05). The results of this study showed that supplement of 0.2% of nucleotide has positive effect on growth and proximate composition in this species.

Mercury is a unique element that, unlike many metals, has no essential biological function. Wide variety of physiological, reproductive and biochemical abnormalities have been reported in fish exposed, but relatively little is known about methylmercury (MeHg) bioaccumulation in fishes and how chronic sublethal exposures affect their functioning. Objective of this study was to investigate the assimilation and bioaccumulation of dietary methylmercury (MeHg) in juvenile Beluga, Huso huso, a commercially important endangered species in the Caspian Sea. In this study four groups of Beluga juveniles were exposed to four dietary treatments with MeHg: 1- Control group (0.04 mg/kg) 2- Low dose group (0.76 mg/kg) 3- Medium dose group (7.8 mg/kg) 4- High dose group (16.22 mg/kg) for a period of 70 days. Results showed that MeHg accumulation was linear during 70 days and in muscle (P<0.05) it was significantly higher in the first 35 days. MeHg bioaccumulation in all treatment groups indicated direct relationship with high dependency between dietary MeHg and MeHg accumulation in muscle (R2=0.0973). Percent assimilation was not significant (P>0.05) among the treatment groups during first and second 35 days, but was higher than second 35 days. It was 57-67% during first 35 days and 42-45% during second 35 days. The results suggested that Mercury contamination could have harmful effects on Beluga even in early years as no exit or transportation for the pollutants exists in the Caspian Sea. The pollutants entering the Caspian Sea through the rivers accumulate in the environment, and a higher amount of them would penetrate into the fish body.

This study was carried out to study the breeding success of Whiskered Tern (Chlidonias hybrida) from June to August in Anzali Wetland (Western part of Wetland). The factors affecting breeding success were studied. Reproductive phonology of whiskered tern started in June with nesting behavior and ended with the fledgling stage in late August. Breeding success was 45.15%. Clutch size varied from 1-4 eggs and cohort groups from 1-2 chicks per nest. There were no significant difference between clutch size and cohort group (P>0.05) but the difference in mortality rate between the different stages of reproduction (P<0.001) was significant. The inability of eggs to hatch and human factors were the major causes of mortality. There was no significant correlation between nest size (P=0.829) and breeding success. It was seen that daily survival rate was higher during the growth of chicks than the in the hatching period and increased until post-nestling stage.

Increase of agricultural activity around the wetlands and use of Organochlorine pesticides in fields lead to widespread contamination of the wetlands. Pesticides are lipophilic compounds with high persistence in the environment and are accumulated in food chain. Aquatic organisms especially fishes are one of the important routes for entrance of these compounds to human bodies. Fish is also a suitable indicator for the organic pollution monitoring in aquatic environment. In this research, concentrations of organochlorine pesticides in common carp (Cyprinus carpio) collected in autumn of 1386 from the Shadegan wetland were assessed using gas chromatography (GC). HCHs (5.81 ng/g ww) had the highest and dieldrin (0.24 ng/g ww) had the lowest concentrations among pesticides. Among DDTs metabolites p,p/-DDE (2.59 ng/g ww), among HCHs isomers a-HCH (5.37 ng/g ww) and among Heptachlors isomers Heptachlor (1.40 ng/g ww) had the highest concentrations. The mean concentrations of pesticides in common carp were below the pesticides standard levels determined by various organizations.

In this research, fluctuations of water level at the mouths of Arvandrud and Bahmanshir rivers are studied. COHERENS which is a three-dimensional hydrodynamic model is employed to simulate salinity and temperature in three dimensions. In this model, Cartesian coordinate for the horizontal and sigma coordinate with three layers is used for the vertical profile. At open boundaries variations of salinity, temperature as well as four main tidal constituents (M2, S2, O1, and K1) are applied. Monthly mean atmospheric parameters (speed and wind direction, temperature, rainfall, relative humidity and cloud coverage) are also employed in the model. In this study, uniform grid of 491×690 is used which covers the region of 40×55 square kilometers of both Arvandrud and Bahmanshir estuaries. In order to validate the results of the model, outputs of the model are compared whit confirmed Admirality Tide Tables and found a very good agreement between them. To compare water level fluctuations of Arvandrud River with Bahmanshir River, some stations were selected along rivers with equal distances from the river mouths. Results of this comparison show that, the speed of tidal wave at Arvandrud River is higher than Bahmanshir River. Also tidal range in the Bahmanshir River found lower than Arvandrud River.

In this study, effect of Gonou hurricane on stratification was analyzed by field data on temperature, salinity and density in Chahbahar Bay. Field data was used to describe the effects of western and south-east winds on the distribution of physical parameters. The salinity distribution before the hurricane event showed existence of Oman sea subsurface water (salinity less than 36.5 psu) in deeper areas of the Bay. Salinity fields observed after south-east wind suggested encroachment of low salinity surface water from mouth of Bay into coastal area by Ekman transport phenomena. One week after weakening of hurricane vertical distributions of salinity and density produced strongly stratified conditions on throughout the Bay. Inflow of open and low salinity waters into the coast and the wind related to the hurricane, together produced a vertical gradient of these two parameters perpendicular to the Bay mouth. Correlation between the different parameters was studied using statistical tests. The circulation pattern in the Chahbahar Bay could be studied using these parameters and analyzing their vertical and horizontal distributions.