JOURNAL OF MARINE SCIENCES AND TECHNOLOGY
Year:2005 | Volume:3 | Issue:4|Papers Count:9

The natural antioxidants effects of f)-carotene in concentration of 100ppm (BC 100) combined with ascorbic acid as a synergist agent (0.lg) and green tea polyphenols in concentration of 200ppm (pp200) on quality of common kilka (Clupeonella cultriventris caspia) during storage with ice powder were studied. Values of PV and TBA at 14, 38 and 62 hour after fishing was compared with control (sample without any antioxidant). Statistical analysis showed although PV and TBA values increased significantly in all treatments (BCl00, pp200 and C) during storage times, but the antioxidant treated samples showed significantly lower PV and TBA values (P<0.005) than the control for the same time period. Sensory evaluation (color, odor, texture, taste and flavor, off flavor) showed no significant differences between both antioxidants; therefore, it is proposed using both antioxidants in preservation of common kilka.

Growth parameters, mortality and exploitation rates were estimated from monthly length frequency samples for Scomberoides commersonnianus in southeastern Iranian waters. Growth parameters estimated with Shepherd's method; K and L¥ (FL) were estimated 0.37 (yea-1) and 122 (cm), respectively; t0 calculated with Pauly formula as -0.30; Von Bertalanffy growth equation for this species was determined as (Lt=122 [1-exp (-0.37 (t+0.30))]. Total mortality was estimated as 1.49 (year-1) with catch curve while natural mortality was estimated 0.6 (year-1) with Pauly empirical formula. Fishing mortality was calculated 0.89 (year-1); exploitation rate was determined 0.59, indicating no fishing pressure on the stock. Longivity was estimated 7.8 years.

Prematuration growth differences of diploid and triploid rainbow trout in the first year of culture (392 day after first feeding) was investigated, using such parameters as weight gain, specific growth rate, and mortality rate of all-female triploid, all-female diploid, mixed-sex triploid, and mixed-sex diploid. Results showed that mortality rate had no significant differences with treatments (P>0.05). Initial weight was significantly higher in diploid populations (P<0.05), also early growth rate of diploid populations was significantly higher than those of triploids (P<0.05). Later growth rate of triploids led to identical weight as that of diploids. Final weight of diploid and triploid (80gr) showed no significant differences between all-female and mixed-sex populations (P>0.05). Although early growth rate of triploid populations was lower than diploids, but due to rapid compensation, it seemed that growth parameters of all-female and mixed-sex diploid and triploid fishes was totally uniformed in the first year of culture.

Dietary phosphorus requirement of narrow-clawed crayfish, Astacus leptodactylus, was determined using five pelleted diets containing equal levels of energy, protein and lipid. Five experimental diets were prepared using a basal diet containing casein, gelatin, dextrin, starch, fish oil, soya oil, vitamin mixture, and mineral mixture tree of phosphorus. Various concentrations of phosphorus (containing of 0, 0.5, 1, 1.5, 2 percentages) provided through adding sodium monodihydrogen phosphate in the basal diet. Crayfish with initial mean weight of 8.16±1.91g was fed experimental diets for 80 days. The diet with 0% phosphorus supplementation yielded the lowest weight gain (1.06g) and the highest weight gain of 2.34g and 2.52g were achieved in the diets containing 1.5% and 2% phosphorus, respectively. There was significant difference between the dietary levels of phosphorus and weight gain (p<0.05). Moreover, the diets with low phosphorus supplementation levels (0-1%) showed the poorer survival rate. Although the lowest survival rate was observed at the 1% phosphorus level and the highest at 1.5% and 2% phosphorus levels, no significant difference (p>0.05) between survival rates in the trial diets was found.Optimal phosphorus requirement in the diet of narrow-clawed crayfish was estimated with broken line regression analysis to be about 1.3%. From these findings, it may be concluded that a dietary phosphorus supplement is necessary for narrow-clawed crayfish. So, it is recommended to use the dietary hosphorus concentration of 1%-1.5% in applied diets formulation.

The gut contents of 73 rainbow trout samples from Khoramnaz river and 32 samples from Beshar river were analyzed to determine the feeding regime. Maximum and minimum length of fish was 46 and 16cm. The highest percent of food items in trout collected from Khoramnaz River belonged to nymph of Plecoptera (41%), Amphipods (15.38%), larvae of Hydropsyche (Trichoptera) (11.11%), larvae of Diptera (9%), and nymph of Ephemeroptera (5%), and in Beshar river belonged to small fishes (Capoeta sp.) (38.88%), larvae of Hydropsyche (Trichoptera) (22.22%), nymph of Ephemeroptera (13.22%), adult insects (11%), crab (9%) and larvae of Tipula (Diptera) (2.84%). Benthos diversity of Khoramnaz river was higher than that of Beshar river. There was a positive correlation between the food items in fish guts and the food items in Beshar river (P<0.01, R2=0.98) and in Khoramnaz river (P<0.01, R2=0.86).

The toxic effects of heavy metals, lead (Pb), zinc (Zn) and cadmium (Cd) were studied on Acipenser nudiventris fingerlings (1-3g) in spring 2005. The experiments were carried out in aquaria holding 20L water in static systems based on O.E.C.D method, using five treatments, one blank and three replicates. In each aquarium ten individual fingerlings were introduced. The LC50 value for Pb, Zn and Cd in 96 hours were 73.825, 21.58 and 0.083 mg/l; (maximum allowable concentration) values of such toxic elements were determined as 7.382, 2.158 and 0.0083 mg/l, respectively.

The red cysts of the green alga (Hamatococcus pluvialis) were grown in Bold medium under sterile conditions. After conversion of red cysts into vegetative cells, they were treated with different concentrations of certain microelements. After two weeks, the results showed that along with the increment of copper, zinc, manganese and iron concentrations in the medium, the dry weight, chiorophyll and astaxanthin content and the amount of dissolved oxygen were decreased. The results suggested that decrement of alga dry weight, probably was due to decrement of cell division in vegetative cells. Besides, because of the inhibitory effects of these elements on the chlorophyll biosynthesis, the chlorophyll content of cells reduced, resulted in reduction of the content of dissolved oxygen, in turn. Due to the conversation of vegetative cells and reduction of chlorophyll biosynthesis and increasing astaxanthin biosynthesis, the latter in the cells noticeably increased.

This project was carried out with the aim of making a suitable net (mesh size, 1mm; total length of filtration area, 143.3cm including cylindrical and conical parts; and bucket volume, 1.7 liter) for catching M leidyi with the least injury, having efficient filtration and the most catch.For comparing it with plankton nets, some samplings were carried out in the two length groups 4-9mm and 12-25mm at depths of6 and 12m at 1m/s speed. Result revealed no significant difference between percentage of intact and injured samples of two nets in 4-9mm length group (P>0.05), whilst in 12-25mm length group, intact sample percentage in the experimental net was more than conventional plankton net (P<0.05). Some samplings were also done at depth of 12m at 1 and 1.5m/s speeds by the experimental net in order to find the suitable speed of towing. Result showed significant difference between the number of injured samples at two mentioned speeds (P<0.05) and the suitable speed of towing net for catching of this animal was obtained at 1m/s. Filtration efficiency at speed of 1m/s was and at speed of 1.5m/s was 0.95.

The effect of five isonitrogenic purified diets with different lipid levels of 4, 7, 10, 13 and 16 percent on the growth, moltung and survival rates was examined for a period of 8 weeks. After termination of the Experiment, juvenile's crayfish fed the diets with 13% lipid gained more weight. Also, crayfish fed the diets with 4 and 7% lipid had significantly lower weight gains than those fed the other diets. Animals fed with diet 4% oil had the lowest and 13-16% lipid the highest molting frequency among the groups. Survival of juvenile's crayfish ranged: trom45 to 80% for all groups, and animals fed the diet 10% lipid had significantly higher survival rate than those fed the other treatments. In conclusion, a dietary lipid Level ranging from 10-13% appears to meet the lipid requirement for this crayfish species.