JOURNAL OF MARINE SCIENCES AND TECHNOLOGY
Year:2007 | Volume:5 | Issue:3-4|Papers Count:11

The feasibility of dietary protein reduction in one meal of rainbow trout of 45.85g average weight was examined. Two iso-energetic diets containing 41.5% and 36.5% protein were formulated. Considering two morning and evening feeding time and two protein levels, four feeding regimes were designated.Treatment one received 41.5% protein in both morning and evening feeding bouts. Treatment two were fed with 41.5% protein in the morning and 36.5% protein in the evening, whereas treatment three was exactly fed in opposite manner. Treatment four received 36.5% protein in both morning and evening bouts. Treatments were fed ad libitum one hour after lightness (artificial light) and one hour before darkness. Photoperiod was 12L: 12D. Reduction in dietary protein from treatment one to treatment four accompanied by reduction in growth, survival, feed efficiency and feed conversion ratio. From these points of view, treatment two and three were moderate. Protein efficiency and production ratio didn't significantly differ among treatments (p>0.05). All of treatments had higher feed intake and subsequently energy and protein in the mornings (p<0.05). Results indicate the possibility of dietary protein manipulation of meal.

This study was carried out to determine the olfactory preference of the Persian sturgeon, Acipenser persicus, of 7-9g to 20 free amino acids, using one positive control and one negative control, totaling 22 treatments. The trials were done in 10 replicates.In the qualitative evaluation of juvenile responses, alanine and to a lesser extent glycine stimulated the strong and obvious feeding (searching) reaction that was also conformed by quantitative evaluation.The amino acids of leucine, histidine, cysteine, also isoleucine and proline promoted a low positive response. The quantitative evaluation verified the result, except for proline. Aspartic acid, tyrosine, glutamic acid and threonine stimulated negative responses as repelling agents. The result of quantitative assay showed the highest negative effect in the case of glutamic acid (p<0.01). Alanine and glycine could be, therefore, considered as appellants and glutamic acid as a repellent for the Persian sturgeon.

Mercury concentration in the muscle, intestine, kidney and gonad of Chalcalburnus chalcalburnus from Anzali wetland was determined in order to compare with international standard levels and also to determine the influence of weight, age and sex on the accumulation of this element in fish tissues. The tissue sample was separated from 23 specimens. Determination of mercury was done by AMA, 254, LECO (Advanced Mercury Analyzer), Standard Method No. D-6722. The mean concentrations of mercury were 70.73, 119.71, 158.69 and 189.13 ppb dry weight in muscle, intestine, gonad and kidney, respectively.No significant difference between age and mercury values was found (p=0.26 for muscle, p=0.15 for intestine, p=0.39 for kidney and p=0.30 for gonad). The same results were also found between sex, length and mercury concentration, but no significant difference was found between mercury concentration in muscle, kidney and gonad and the variable of weight (p=023 for muscle, p=0.13 for kidney and p=0.72 for gonad). There was, however, a significant difference between mercury values in intestine and the variable of weight at confidence level of 95% (p=0.03). Comparing mercury concentration in muscle (70.73 ppb) with standard threshold levels, it was lower than that of WHO (500 ppb), FAO (500 ppb) and FDA (1000 ppb).

In this study, Population dynamics and biomass of the invasive Polychaete, Streblospio gynobranchiata, in 1, 2 and 3 meter depths of the Gorgan Bay (Bandargaz Coast) was studied in the years 2004-2005.Results indicated increased density and biomass as depths increased. The average density of this worm in 1 and 3 meter depth was 1147±796 /m2 and 2894±1137 /m2, respectively; the average biomass in the respective depths were 0.31 ± 0.15 g/m2 and 0.614±02 g/m2. The highest density and biomass in 1 and 2 meter depths were encountered in autumn; in 3 meter depth, The highest density was observed in summer while the highest biomass was observed in summer and autumn. The lowest density and biomass at all depths observed in winter.

The possibility of wave height prediction in the Anzali coastal area was investigated using the WAM numerical model. Input data ware speed & direction of winds and hydrography of the region which were respectively provided by Anzali Meteorological Station and Gillan Port and Shipping Bureau. The time interval between two wind data was 1 hour and the total time of measurement was 6 months. The model results were validated by comparing them with measured wave height data by an I.R.I navy vessel.The results revealed that wave height forecastings could be fairly performed in the Anzali coastal area, using the nemercial WAM model. However, provision and application of more densely and suitably distributed wind data over the region is necessary to increase the accuracy of predictions. Model errors in the near-shore region were less than the erros in offshore region. Moreover, results revealed that maximum and average wave heights in 6-months prediction period were 2.6 m and 0.65 m, respectively.

Reproduction biology of silver pomfret from Bandar abbas waters during April 2005 to March 2006 illustrated long spawning period from March to September. We seldom observed spawners in that period and most of the females were in stages 2, 3 and 5, indicating the area is not spawning ground for silver pomfret. First length of female maturation (Lm50) was 24.8 cm (F.l). Condition factor was 0.00536 g/cm3 and from February to June it had the best growth rate. Weight-length relationship was w =0.00002× L3.0902 and b doesn’t significantly differ from 3 (P>0.05).

Effects of two protein levels and different carbohydrate to fat ratios on growth factors, feed and protein efficiencies (FE & PER), hepatosomatic index (HSI) and body composition of juvenile beluga (Huso huso) with average weight of 894.4 ± 9.0gr were studied. Juveniles were fed four times a day up to satiation for a period of 16 weeks with 8 different diets containing two levels of protein (40 & 45%) and four ratios of carbohydrate to fat (1.7, 1.4, 1.1 and 0.8).Under the various carbohydrates to fat ratios, increase in protein from 40% to 45% resulted in improved weight gain and FE (P³0.05) and significant increase in PER (P£0.05). Low carbohydrate to fat ratio (0.8) resulted in decreased growth rate (P£0.05) as compared to fish fed with higher or medium ratios (1.7 and 1.1). Analysis of body composition showed that regardless of protein and carbohydrate ratios of diet, fat in the body was directly correlated with the fat content of the diet and reversely correlated with the body moisture (P£0.05). Fat content in fish significantly increased with decrease in carbohydrate to fat ratio (P£0.05). The highest HSI was observed in fish fed with 1.7 carbohydrates to fat ratio. On the basis of growth indices, diets containing 40% protein, 23 to 24 % carbohydrate, 16 to 17% fat and a carbohydrate to fat ratio of 1.4 are preferable for juvenile Huso huso from the weight of 800 to 1900 g in terms of physiology and economy.

Zooplankton distribution and frequency in three earthen ponds of warm water fish were studied for a period of 7 months. Totally 24 genera in 3 phyla of Rotatoria, Arthropoda and Protozoa were identified.Rotatoria with 16 genera dominated the zooplankton diversity (67.7%), while arthropods with 3 genera comprised the lowest diversity (12.5%). Rotatoria comprised the highest density (357 ind L-1 or 71.6%), followed by Protozoa (72 ind L-1 or 14.5%) and Arthropoda (6q ind L-1 or 13.9%). The highest density (622 ind L-1) was encountered in summer. The highest density (885 ind L-1) was encountered in August and the lowest (108 indL-1) in April. No significant difference (p³0.05) in zooplanktonic production among the three ponds was observed. Gut content analysis of 27 fish samples (18 common carp and 9 bighead carp) revealed that Rotatoria was a more preferable zooplankton than the other two phyla.

The reproduction characteristics (spawning season, sex ratio, maturity stages, fecundity and oocyte diameter) of javelin grunt, Pomadasys kaakan, was studied in the Hormuzgan waters of the Persian Gulf by collecting a total of 415 specimens during years 2005-2006. The maturation and spawning behavior were investigated based on macroscopic observations of gonads, histological cross section and determination of GIS and maturity stages. The spawning was found to occur from May to July. The biometric measurements showed that maximum TL was 61 cm and according to the growth curve, this species has an isometric growth. The total sex ratio was calculated as (M) 0.98: 1.0 (F) that was not significantly different from normal ratio of 1:1. The maximum absolute fecundity and oocyte diameter were calculated 1874814, and 0.61mm (stage 5), while the minimum fecundity and oocyte diameter of 268296 and 0.04mm were found in stage 2 respectively. As a conclusion, Pomadasys kaakan is a partial synchronist and total spawner.