JOURNAL OF MARINE SCIENCES AND TECHNOLOGY
Year:2005 | Volume:4 | Issue:1-2|Papers Count:10

Heavy mortalities occur during the critical period of early stages of the Persian sturgeon, A. persicus, development. These mortalities may be caused by yolk sac absorption, endogenous feeding change to exogenous, incomplete development of immune system, etc. This study was performed to determine the effects of levamisole as an immunostimulator agent on mortality reduction in the Persian sturgeon fry. The experiment included one control and two treated groups in which 5 and 10 mg/l levamisole were applied on daily bath for 20 min. In order to determine the days of critical period during the early stages of development and to study the levamisole effect on mortality reduction, daily mortality percentage was calculated in treatment and control groups. The results showed that critical period in the Persian sturgeon was on days 11 to 13 after hatching. In this investigation, early mortality rates were 6%, 4% and 3% in the control, 5 and 10 mg/lit levamisole treated groups, respectively. The survival rate was 71.05%, 76% and 87.05% in the control, 5 and 10 mg/lit levamisole treated groups, respectively. The result showed that levamisole was capable to decrease mortality rate and increase survival in fry of sturgeon significantly (p<0.05).

The Possibility of enriching Artemia urmiana with probiotic bacteria by using the blends of five strains of probiotic endospor-forming gram-positive bacillus was evaluated in March 2004. This experiment was done in a completely randomized design and in four treatments of the blends of probiotic bacillus (Aqua 1, 2, 3 and 4) with concentration of 3.18×105 bacteria per ml in suspension of broth. For evaluation of the possible enrichment of Artemia nauplii with each bacterial blend at t0, t0+5, t0+2, t0+4, t0+8, t0+10 and t0+24 hours after the commencement of bioencapsulation, samples were taken by volumetery method from nauplii and after bacterial culture, the number of bacteria from each blend was counted .The results indicated that the incorporated bacteria into nauplii in all the treatments increased with passing time; there was a significant positive correlation (p<0.01) between the encapsulation time and number of bacteries in nauplii, Bacterial blend of Aqua 3 had the highest level of CFU/nauplii (5.36±0.36×103) in 24 hours, which was significantly different from other bacterial blends (p<0.05). The experiment showed that the possibility of enriching A.urmiana with of probiotic bacteries was relatively high and also its behaviour in relation to different bacterial blends was completely different.

Many factors such as wind, tide, density and pressure gradients cause oceanic and marine currents. For the reason that the density of layers are different, therefore the more dense layer moves in direction of the less dense layer and consequently Quasi-Geostrophic currents are formed. In this study, we have considered the northern coasts of the Persian Gulf. In addition, the governing equations have been solved using the method of finite difference and considered stability, boundary and initial conditions appropriately. The components u and v have been obtained using the information of 30 stations and calculating the slope between two layers with considering depth and density variations in direction latitude (26o 25' to 28o 11') and longitude (49o 71' to 52o 34'). The results are in relative good agreement with the results of the other mathematical models that have been already obtained for the Persian Gulf. Based on this study, for the spring season, the maximum of velocitiy is about 0.01 (m/s) and the minimum is 0.0001 (m/s).

The influence of short-term storage (3, 6 and 9 h) of the Persian sturgeon (Acipenser persicus) ova outside of ovarian cavity in coelomic fluid and PSACF media at 4ºC and 18ºC was studied. One mature female and three mature male were selected for this experiment. They were injected and their milt and ova were collected according to common method, then ova filtered and coelomic fluid separated and used for storage purposes. For mimicking of ovarian fluid and designing PSACF media, chemical compositions of ovarian fluid of 26 samples (from 18 females) were analyzed separately. Osmolarity and pH for each sample were determined and PSACF medium formulated.This experiment was performed with 12 treatments in three replicates. For each treatment, 5 cc ova (about 300) were used. After onset of storage (3, 6 and 9 h) ova were fertilized with pooled sperm and then transferred to Yoshchenko incubator and fertilization, hatching and malformed larvae rate were assessed.Results showed that storage period and medium had significant effect on fertilization, hatching and malformed larvae rate (P<0.05). Also ova holding temperature had significant effect on fertilization rate but its effect on hatching and malformed larvae rate was not significant (P≥0.05). Fertilization and hatching rate decreased with time but malformed larvae rate increased comparing whit control. Interaction effects between time and medium and temperature of storage on fertilization, hatching and malformed larvae rate was significant (P<0.05(. In conclusions, results of the optimized treatment showed that using of PSACF media at 18ºc for 3 h in relation to fertilization, hatching and malformed larvae rate were about %80.33, 570.5 and%2.6 respectively.

A 3×2 factorial feeding trial of three dietary protein levels (45, 50 and 55%) and two dietary crude energy levels (4200 and 4600cal/g) with three replications was coducted to investigate the proper dietary protein and energy levels for the growth of fingerling Caspian trout (Salmo trutta caspius). Fingerlings with average weight of 3.8±0.1g were fed the experimental diets for 60 days. Results indicated that weight gain, FCR, SGR and PER were affected significantly by dietary protein and enaegy levels (P<0.05). At the constant protein levels, growth performance of fishes  improved as dietary energy levels increased (P<0.05) and at the constant energy levels, growth indexes at first increased  and then decreased significantly as deitary protein level increased. Growth performance of fish fed diet with 50% protein and 4600cal/g energy significantly (P<0.05) was better than other treatments. Protein content of fish increased when dietary protein increased but there was no significant difference (P>0.05) between 50 and 55% protein. Lipid content of fish fed higher protein levels was significantly (P<0.05) lower than those of fish fed lower protein levels. Moisture and ash contents of fish were not affected by dietary protein levels. Lipid content of fish fed diet with high-energy level was significantly higher than those of fish fed the low dietary energy (P<0.05). This case was converse for body moisture. Protein and ash contents of fish also were not affected by energy levels. It can be suggested that for this size of the Caspian trout, diet with 50% protein and 4600cal/g energy is appropriate.

Length frequency data based on monthly samples were used to estimate growth parameters (K, L¥ (FL)) and mortality rate of Scomberomerus commerson in southeastern Iranian waters (Hormozgan Province) during 2003-2004. The von Bertalanffy growth parameters were estimated as K= 0.42 (year-1) and L∞ (FL)=140 cm, and t0 calculated using Pauly formula as-0.26, which gives Von Bertalanffy growth equation for this species as (Lt=140[1-exp-0.42(t+0.26))]. Total mortality was estimated as 1.47 (year-1) with applying length converted catch curve. Natural mortality was estimated as 0.49 (year-1) using Pauly empirical formula. Fishing mortality was calculated to be 0.98 (year-1). The relationship between weight and fork length can be expressed as W=0.0076FL2.9826. This equation indicates that the Spanish mackerel has isometric growth pattern. Several indicators suggest that stocks of this fish are under intense catch pressure and, therefore, stock management of this species should be implemented rapidly to maintain their sustainability.

In this paper, we attempt to express equations for sound reflection and scattering coefficient from surface and bottom. We used two scales model (TSM) in modeling of the ocean surface scattering coefficient. In this model, the seas spectrum is divided into large scale and small scale parts. The large scale part forms the main lobe of the scattering index. The small scale part forms a halo and defines the backscattering. Hence, equations 12, 14, 15, and 16 will be defining as reflection and scattering coefficients from sea surface and reflection and scattering coefficients from bottom respectively.

The efficiency of several quality evaluation indices was assessed to determine the effect of steam cooking on common Kilka quality. For this purpose, samples were cooked by saturated steam (102-103oC) in a retort with 1.02 atmospherics pressure for 15 minutes. Qualitative characteristics, including total lipid, free fatty acids, tiobarbituric acid contents and the profile of fatty acids in raw and cooked fish were determined and compared with fluorescence contents (aqueous and organic phases) of lipid extract obtained from those samples. Results indicated the fluorescence method as a good technique for degradation quality assessment of cooked product compared with other methods.

Tadpole shrimps are common inhabitants of temporary freshwater ponds. First sample of Triops was collected in spring of 2004 in water bodies of the vernal pools around Urmia Lake. Then morphological characteristics of Triops by low power and compound light microscopes were investigated. The body (Total length=4.4cm) consists of a head and trunk and is mostly covered by the large dorsal carapace (length=1.69cm). The trunk consists of a thorax with segmented appendage but abdomen segments bear no appendages. The oral region of the cephalon possesses specific appendage types including antennules, antennae, maxillae and mandibles that are covered by a labrum and used for food handling. The anterior thorax consists of 11 segments and each bears a pair of appendages (thoracopods). The 11th appendages of females form brood pouches. The many appendages posterior to the 11th move the spent feeding and respiratory current away from the body and are also for respiration. The proximal portion of the abdomen possesses 66 pair of fine, hair-like appendages that beat in rhythmic fashion to assist in movement and food channeling. The distal portion of the abdomen terminates into a prominent telson and subsequently branches into two large caudal furca (length=2.14).