Iranian Scientific Fisheries Journal
Year:2003 | Volume:12 | Issue:3|Papers Count:18

This study was carried out from August to November 2002 in the Iranian coastal waters of the Caspian Sea (Guilan province). The results showed that gut contents of Mnemiopsis leidyi included a wide variety of prey including 84% of zooplanktons and 16% of phytoplanktons. The most abundance of intaked foods was Acartia (belongs to Copepoda) with 34% frequency and the least was podon (belongs to Cladocera) with 0.74% frequency. Also 3.0% of fish eggs and 4.2% of molluscs were found among stomach contents. Maximum and minimum fed phytoplanktons were Chrysophyta (67.0%) and Pyrrophyta (3.7%), respectively. The young specimen consumed more zooplanktons and phytoplanktons comparing to adult ones. According to laboratory observations, this ctenophore cannot digest phytoplanktons.

The effect of different bycatch reduction devices in decreasing bycatch of commercial fish species with the length of less than LM50 (the length from which, 50% of them are matured) in shrimp trawlers were examined. The experiments were conducted in Persian Gulf (Bushehr and Hormuzgan provinces) during the shrimp season, years 2000-2001.In this study four types of bycatch reduction devices (Grid, Nafted, Fish eye and Square mesh window) were used. Double rig trawl was used, one of them as an experimental trawl and the other as the control.Different treatments like one device or two devices were installed on experimental shrimp net. After hauling the trawl, frquency of different commercial species with length less than LM50 was determined in both nets, and the results were tested with Paired Willcoxon test. The results have shown that although all the devices have a reductional effect on bycatch of the young and juveniles of commercial species, but the amount of reduction with setting Nafted and Grid, either single or combined with another BRD was significantly higher than the control one (P ≤ 0/05). The amount of by catch reduction devices with different treatment (different devices either single or paired) according to the season of the experiment were also tested with Kruskal- Wallis test, which shows significant differences (P≤0.05) between the frquency of young and juvenile individuals of some species during different experimental seasons.According to this study, by using Nafted and Grid devices in the trawl nets of all shrimp vessels during its season, about 400 to 500 thousand of juveniles and young individuals can escape from the nets.

In this study, the fluctuation of two parameters of blood glucose and cortisol hormone were investigated in different salinities in Cyprinus carpio.Seven tanks with 100 lit. volume were used and different salinities of 0, 3, 6, 12, 15 and 18 ppm were choosen as treatments. Then, 16 specimen of common carps (each 50-90 g weight) were added to the tanks.In periBds of 12 up to 96 hours, the blood sample was taken from each fish for further measurment of parameters.The results showed that all fishes died at 18 ppm salinity within less than 12 hours. The blood glucose indicated high sensitivity to the higher salinity.In this research, blood glucose had a reange of 13.5 to 321.0 mg/dc.lit and also, cortisol showed a fluctuation from 10 up to 70 µg/dc. lit and its concentration had a direct relationship with increasing the salinity.

The brown algae of Sargassum glaucescens is found all along the coastal waters of Sistan and Balouchestan province in the Oman Sea. This species as a raw material can be used in different industries and is considered as an economical marine resources.In order to determine the distribution pattern and biomass of this species eleven growing regions were surveyed from Gwatr area in east and Miedany in west. The sampling were carried out monthly in inter-tidal zone and seasonally in subtidal zone. After sampling, the wet-and dry weight, mean length of taIls and number of branches were measured. Also, some physical and chemical parameters were measured.The results showed that brown algae is distributed all along the studied area in the second half of the year, meanwhile in the Gwatr area is found all seasons. The mean biomass of S. glaucescen,y in Gwatr, Chabahar, Tang and Galak was estimated 629.9, 235.5,314.4 and 127.5 g/m2, respectively.

Jajroud river is one of the most important aquatic ecosystem in Iran (east of Tehran) and consist of variety of different aquatics, of which is a freshwater crab. The crab sample were collected from 5 stations of Taraghion, Khojeer, Latian, Daroee plants and Mamloo dam.The collected samples were studied from point of reproduction and feeding behaviour; and also, carapace length, carapace width and body weight were measured.The most important objective of this survey was to find out the precise species identification. In this regard, sample were transported to the Natural History Museum in Netherland and ultimately, it was certified that all specimens belong to Potamidae family and species of Potamon persicum.

The alien ctenophore Mnemiopsis leidyi which was transported from the Black Sea into the Caspian Sea at the end of 1990s has been negatively affecting ecosystem in this new environment. In this study, spatial and temporal distribution of M.leidyi were studied from a total of stations located along three transects (Amirabad, Babolsar and Nowshar) in the Eeastern Iranian coasts of the Caspian Sea (Mazandaran province) during July 2001 to November 2002.M. leidyi acheived maximum biomass 1024.5 g/m2 in August-October 2002. Minimum biomass (1.5 g/m2 of ctenophore were measured in December-Jaunuary 2001. The highest biomass was at the stations with 10m bottom depth (570.7 g/m2 in autumn and lowest biomass (75.9 g/m2) was obtained at a station with a 50 m bottom depth in winter. The highest average biomass (641.2 g/m2) were measured in ~irabad region and the lowest biomass (207.5 g/m2) observed in Nowshar region.The young specimens (<5 mm) contributed about 90% to the total abundance of the population. The maximum length was 51-55mm which was measured in August. The factors affecting the distribution of M. leidyi in the study area were discussed.

The zooplanktons were studied in spring, autumn and winter in the southern Caspian Sea in 1996. Sampling carried out in four season. In each season, 180 specimens were identified and their frequency calculated per m3. 55 species of zooplanktons were identified including 55% Cladocera, 15% Copepoda and 11 % Rotatoria, 9% other groups such as meroplanktons. The maximum species diversity was observed for Cladocera and the maximum frequency were observed for Copepoda. The Copepoda affected on abundance of zooplanktons as this frequency included in spring, summer, autumn and winter that were 38% to 97%, 22% to 92%, 71 % to 99% and 31 % to 92%, respectively. In summer, the Copepoda and lamellibranchiata larvae had main role in formation of zooplankton population in western region of the southern Caspian Sea, but in autumn, 70% of zooplankton population were copepods. The frequency of zooplanktons in spring, summer, autumn and winter were calculated 4081 to 20143; 7812 to 65741; 10850 to 34406 and 4510 to 20576 ind./m3, respectively. The maximum biomass was observed during summer with 200 mg/m3.

The Anchovy kilka, (Clupeonella engrauliformis) is the most commercially important of the caspian kilka. The poor quality of many processed products is due to poor quality of raw material in which the quality of fat is a contributing factor of great importance. In this study, samples from fishing vessels were transported and stored under two metods of Chilled Sea Water (CSW) and Boxed with ice powder. In Chilled Sea Water method, containers were filled with ratio of 60, 25 and 15 percent of fish and ice and sea water, respectively. Then their qualitative characteristics such as moisture content, total lipid, phospholipid and neutral lipids, peroixids value, free fatty acids, heme iron and tiobarbituric acid content, organic phase fluorescense. Statistical analysis of results showed that CSW was a better method for maintaining the quality.

Samplings were carried out weekly in coastal waters of the Guilan province (Caspian Sea) by a hand net with 0.5mm mesh size during 1996-1997.The results of one year sampling showed that the mean total length(T.L.) of this shrimp (pooled data of females and males) was 28.58±5.58mm (x±SD), and were 26.46±4.30 and 30.01±6.30mm in males and females, respectively. For ovigorus females, mean T.L was 36.16±3.13mm, also the minimum and maximum T.L of the males were 12.6 and 41.1mm, respectively. In females these figures were found 10.7 and 43.4mm, respectively.The length-weight relationship for the males and females were determined as W=0.0002 TL2.97 (R2=92.13) and W=0.00002 TL2.98 (R2=92.84), respectively. Spawning season was determined from May to September. The average absolute fecundity was 796±320, with a range of 360 and 1660. There is a direct retationship between fecundity and T.L.Females provided 59.42% and males 40.56% of the population, the sex ratio deviated from 1:1 (P<0.05).The growth coefficient of Loa for females, males and pooled data based on powell-wetheral methods were 42.6, 34.4 and 42.5, respectively. The growth coefficient of K based on Shepherd method were 2.1, 2.3 and 2.5 for females, males and pooled data, respectively. Natural mortality rate (M) calculated as 2.29, 2.29 and 2.28 per year for females, males and pooled da1a, respectively. Total mortality rate was calculated as 2.38, 2.50 and 2.61 per year for females, males and pooled data, respectively.

The coastal zone of the Oman Sea (Sistan and Baluchestan province) with 300 Km length is a rich habitat of different species of seaweeds. In order to determine the species identification and distribution of seaweeds, 11 stations were selected and samplings were carried out seasonally by scuba-diving method.During this study, 42 species of seaweeds were identified consist of: 3 species of green algae, 17 species of brown algae and 22 species of red algae. The dominant species of brown algae were: Stoechospermum marginatum, Padina australis, Dictyota sp., Sargassum glaucescens and Cystoseira indica.Some important and commercial species of red algae are: Gracilaria corticata, Gelidiella acerosa, Gelidium micropterum, Hypnea musciformis. The green algae were found only in Passabandar and Chabaharegions with the main species of Ulva fasciata.Along with sampling, some environmental factors were measured including: sea and ambient temperature, salinity, pH, growing depth, D.O., substrate structures and slope and transparency. The maximum and minimum growing depth of seaweeds were found in Tang and Gwatr areas, respectively.

In this study, immunoglobulins from serum of Persian sturgeon (Acipenser persicus) were purified and partially characterized. Immunoglobulins were purified from the pooled sera by a combination of salt precipitation, Ion-exchange chromatography and gel filtration methods. DEAE sepharosefast flow and sepharose CL-6B columns were used for Ion exchange-chromatography, and gel filtration, respectively. The purity, molecular weight and molecular distribution of the immunoglobulin preparations was determined by gel electrophoresis (SDS-P AGE) in reducing and non-reducing situations.In gel filtrated immunoglobulins two distinct peaks, high molecular weight (HMW Ig) and low molecular weight (LMW Ig) were obtained. Both HMW Ig and LMW Ig had identical heavy and light chains of 72-75 KDa and 27-29 KDa, respectively, in reducing SDS-P AGE. HMW Ig contained a group of bands, including two major bands in non-reducing SDS-PAGE, In contrast LMW Ig contain more than half of the total immunoglobulin, was 190 KDa. In ion exchange chromatography, immunoglobulins were eluted in three peaks. The first was exclusively monomer and others were mixture of monomer and polymers. This is the first report on persian sturgeon immunoglobulins. Results of this investigation showed that persian sturgeon immunoglobulins was not homogenous in respect of molecular distribution, PI and the type of light chain. The presence of more than one genes for light and\or heavy chains or post transcriptional and\or post modifications may be responsible for these variations.

The objective of this study was to evaluate the seasonal fluctuation of density and biomass of cyanophyta in different water temperatures in the southern Caspian Sea in 1996 and 1999-2000.432 samples of phytoplanktons were collected from 18 stations in coastal zone (depth less than 10 m).As a result, 11.1% (9 species from 81) and 15.6% (25 species from 160) of total phytoplanktons were cyanophyta in years 1996 and 1999-2000, respectively. The maximum density and biomass (1.65x106/m3 , 4.09 mg/m3) of Cyanophyta were found in the western region and in warm seasons (spring and summer). On the other hand, in cold seasons (autumn and winter), the maximum density and biomass (1.5x105fm3, 3.36 mg/m3) were found in the eastern part of the Caspian Sea. In years 1999-2000, the maximum biomass and density of Cyanophyta were found in eastern, central and western parts of the Caspian Sea in spring and summer, meanwhile in autumn and winter, they were found with maximum density and biomass in the eastern part.In all seasons, the minimum and maximum water temparture were measured in the western part and eastern part of the southern Caspian Sea, respectively.The results showed that the most density of cyanophyta were measured in summer that can be related to the increase of temperature and daylight. The non-parametric statiscal analysis indicated that there were no significant difference between biomass and density of cyanophyta in years 1996 and 1999-2000. As a conculsion, the population dynamic of cyanophyta were mostly affected by combination of enviromental factors than effect of a single factors sperately (such as temperature).

Studies showed that Thyroxine can play an important role on fish growth, osmoregulation system, and other physiological activities. Since the direct effect of thyroxine on growth and metamorphose of bony fish larvae has not been yet approved, therefore, present study were carried out in Shahid Ansary propagation and cultivation farm in order to find out the way of effect of this hormone on the survirval rate and early growth stage of silver carp (Hypophthalmichthys molitrix) fertiled eggs that were bathed in thyroxin with concentrations of 0.1, 0.5 and 1.0 ppm (each one, replicates) for 6 hours. Then they were transfered into large incubators (zoog) with running water. After hatching all larvae were placed in mentioned thyroxin concentration bath for another 6 hours before being transfered into large incubators.Larvae stayed inzoogs until the yolk-sac was absorbed. Finally, live silver carp larvae were counted in separated plates. Results of present study indicated that the ra tio of hatched eggs in 0.5 ppm of thyroxin concentration was higher than other treatment.

Management of commercial catch of the spiny lobster, Panulirus homarus Linnaeus, 1758; was studied in fishing season, from September to November 2001. P. homarus specimens were captured from different fishing sites of Ramin, Chabahar, Konarak, Puzm and west of Puzm. Carapace length and sex of specimens and presence of eggs and pleopods of females were considered. The latter factor was noticed to check of the eggs removed from pleopods. Fishing season takes about one and the half months. The maximum and minimum carapace length were observed in west of Puzm (80.04 + 9.02 mm) and puzm (76.46 6.66 mm), respectively. Minimum size limit specimens at different fishing sites were not significantly different, but frequency of them were more than years of 1999 and 2000, although fewer ovigerous females were caught.A better management of the lobster resources needs the collaboration on fishing, fisheries and research within the Iranian authorities, and also fisheries cooperation of the two neighboring countries.

About 125 young Huso huso specimens in the +1 year class with a mean weight of 761.5±2.7 g were selected for this study. The speciemens were studied in four experimental groups and three replicates were run for each group. In the first group one barbel on the right was clipped, in the second group two barbels on the right were clipped, in the third group 3 barbels on the right and one barbel on the left were clipped and the forth group were considered as the control group without any ablading of barbels. Fishes under this study were fed with diets composed of kilka and formulated diets. Growth conditions in the fishes were studied through the six weeks experimental period. On the basis of results obtained no significant differences were observed among the different treatment.