JOURNAL OF MARINE SCIENCES AND TECHNOLOGY
Year:2004 | Volume:3 | Issue:2-3|Papers Count:11

The effects of four phytoplanktonic diets including Isochrysis galbana, Chaetoceros sp., Tetraselmis sp. And a mixed diet of them on feeding and reproduction of the copepod, Acartia clausi, under laboratory conditions were investigated using parameters such as egg and faecal pellet production rates, and hatching success as indicators. Egg production rate per female per day varied with diet type, being highest when fed with the mixed, and lowest with Tetraselmis sp. No significant differences (p≥0/05) were found between I galbana and Chaetoceros sp. diets in egg production rate. Hatching success rate was not found so different when copepod was fed with the individual diets, but significantly different (P≤0/05) when fed with the mixed diet.As for the faecal pellet production rate, no significant difference among the four types of diets was found (P≥0/05), indicating all the diets were accepted by the copepod. There was a close relationship between egg and faecal pellet production rates. Food type had effects on female longevity and also fecundity. It could be concluded that mixed diet was the more suitable food among the four types fed to the copepod; individual diets, I. galbana and Chaetoceros sp. were found to be important in feeding of copepod, but not the Tetraselmis sp. for this purposes.

We studied the effect of permeability on wave reflection by Mansard method with 3 wave height meter sensors applied in wave flume. By increasing of fluid head, some of it penetrates into bed which called suction. In this case streamlines are close to bed and velocity near bed increases that result in bed stress increases by factor 2.5. On the other hand, by decreasing the fluid head, it leaks out of bed, called injection, which results in -decreased mean velocity near bed and 70% decrease in stress. Reflection factor of waves decreases at coasts for the same permeability by increasing wave steepness. By increasing of wave breaking similarity parameter, the wave reflection parameter increases about 2 times. We conclude that the reflection parameter reduced by increasing permeability . We used 7 regular waves with range of steepness from 0.02 to 0.04 in deep water to study effects of permeability on wave reflection as well. As for the bed currents, by increasing its slope to (1:3), for very low, low, middle, and high permeabilities, results are in agreement with the previous studies, but there is a slight difference in current shape.  

We have compared and used long duration data for temperature, precipitation and evaporation in the northern stations of the Persian Gulf to assess their effect on currents and climate of this region. Based on our result, the average annual temperature has increased about one degree in recent years. This would have caused variations in evaporation, precipitation and wind speed that, in turn, would have clearly affected the Persian Gulf currents. These variations are clearly observational on Persian Gulf currents.

An 8-week feeding trial on the effect of supplementary optimun at 0.15%,0.25% and 0.35% of feed was evaluated on the growth and survival rates of beluga juvenile, Huso huso, in Shahid Marjani Sturgeon Hatchery (Agh-ghala, Golestan province).The trial was carried out in 500 liter PVC. tanks, filled with about 350 liter of water. Twenty-five juvenile beluga (average weight 21.2±1.04g) were stocked in each tank and fed five meals a day. Growth and survival index were analyzed at the end of trial period. The results showed that the addition of optimun led to improved body weight (BW), weight increase percentage (BWI), specific growth rate (SGR), condition factor (CF), survival rate(SR), price index (PI) and decrease of food conversion ratio (FCR) as compared with control treatment. The best value of growth improvement index was achieved at dietary level 0.25% optimun.  

Food interaction of waders and aquatic organisms including species composition, food structure and preference as well as benthic macrofauna composition, substrate structure, TOM, biotic indices and interaction of macrofauna food constituents and waders were investigated in Khur-e-Musa from Dec. 1999 to Aug. 2000 (8 months). In this study 99 birds belonging to 5 families, 10 genera and 14 species were hunted from Dawragh and Zangee creeks. The highest abundance of waders belonged to dunlin, ringed plover and red shank. Analysis of gut contents revealed that the highest abundance of food item belonged to Eurycarcinus sp. gastropods, beetles and diptera. Birds composition revealed that the highest number in Dawragh and Zangee creeks belonged to dunlin, ringed plover, red shank (categorized as winter wading species) and little ringed plover (categorized as spring species index in breeding season). The highest abundance of macrofauna belonged to Eurycarcinus sp., gastropods, amphipods, polychaetes and bivalves. The bottom of estuaries was silty. Shannon index (1<H'<3) indicated the studied area was intermediately polluted. Species richness for birds and macrofauna in Zangee creek was higher than Dawragh creek. There was a positive correlation between bird's diversity and food items and this correlation in.Zangee creek was more than Dawragh creek.

To identify dominant bacterial genera of invading comb-jelly (Mnemiopsis leidyi), samples were collected in triplicates from 5, 10 and 20 meter depths of the Caspian Sea. Samples were first homogenized in sterile normal saline and, then, were inoculated on tryptic soya agar at 30˚C for 72 hours. The morphological, physiological and biochemical characteristics of the grown bacteria from the second passages on tryptic soya agar were studied using standard bacteriological examinations. Genera of Corynobacter spp., Enterobacter spp., Vibrio spp., Psedotubercolosis spp., Listeria spp. and Yersinia spp. in samples from 5 meter depth, and Micrococcus spp., Enterobater spp., Listeria spp., Actinobacillus spp., Vibrio spp. and Morganella spp. were identified in samples from 10 meter depth. In addition, genera of Vibrio spp., Enterobacter, Aeromonas spp., Micrococcus spp., and Morgunella spp., were characterized in samples from 20 meter depth.Results showed that Vibrio spp. and Enterobacter spp. were dominant bacterial genera in samples from 5 meter depth, while Listeria spp. Vibrio spp. and Enterobacter spp. were dominant in 10 meter depth; Vibrio spp. and Enterobacter spp. were dominant bacterial genera in samples obtained from 20 meter depth.

The effect of exogenous hormones of HCG, LRH-A2 and CPH on the plasma steroids level and the oocytes maturation in grey mullet, Mugil cephalus, was examined in vivo, using saline solution as control. Sexually mature female grey mullets were captured from pond and injected with saline solution, HCG, LRH-A2 and CPH. Blood samples were taken from 12 females after 48 hours from the first injection of a two-injection protocol. During hormonally induced spawning, mullet exhibited an initial increase in serum testosterone and estradiol-17β compared to saline-injected controls. In spawned and unspawned mullets both steroids fell 24 and 30 hrs after the first injection, respectively. Peak levels of l7α -hydroxyprogesterone in spawned fishes occurred 30 hrs after the first injection. These changes coincided with ovulation. The plasma 17α-hydroxyprogesterone level in unspawned mullets increased to the end of experiment. No change in 17α- hydroxyprogesterone was observed in saline-injected controls. This suggests that this steroid is one of the maturation-inducing substances for this teleost.

Effects of probiotic protexin at 4 doses of 0.15, 0.5,1 and 1.5 g/ kg food on the survival and growth of rainbow trout larvae was investigated, using diet with no protoxin as control. Each treatment tray, with dimensions of 42.5x42.5 cm, was stocked with 265 trout larvae of 90±0.2mg average weight. The experiment was carried out in four replicates. Feeding percentage was ranged between 4%-7% of larval body weight.After 60 days feeding trial, it was found that larvae fed with 0.15g protexin/kg food had better growth performance than control (P<0.05). Also survival in larvae fed with 0.15g and 1g protexin /kg food was significantly higher than the with control (P<0.05).

The role of the Caspian Sea in precipitation in the southern coasts along Iran was investigated, using meterological data and analysis of synoptic maps. Results show that three kinds of air mass and pressure system affect precipitation in the southern coasts: Siberia High Pressure, Low-Pressure Systems and Emigrant Anticyclones. The most frequent precipitation originates from SHP while the highest and strongest precipitation originates from EA. Evaporation from the Caspian Sea provide moisture for precipitation that originated from SHP, while moisture for LPS and part of moisture for EA is provided by the Black and Mediterranean Seas and Atlantic Ocean. The necessary condition for intensive precipitation to take place in the area is when the high pressure ridge on the earth surface and trough in the middle and upper level of atmosphere are provailed. It should be pointed out that cold air, transferred from high latitude to the south shores of Caspian Sea, brings about increase in air pressure in the area. With due attention to season and high temperature of sea water, when cold air passes over sea, the lower part of it becomes warmer and more humid and consequently become unstable. This humid and unstable air will be driven to the south coasts of sea by an anticyclone air stream. Trough in the upper level supports climbing streams, so the higher pressure in the earth surface and deeper trough in upper level, the more intensive precipitation is expected.