مجله علمی شیلات ایران
سال شانزدهم شماره 2 (پیاپی 59، تابستان 1386)

Brachionus calyciflorus is a freshwater rotifer that is used as a live food for intensive production of freshwater fish larvae. In this research, the possibility of isolating, purifying and semi-intensive production of freshwater rotifer was investigated in laboratory condition. Sampling was done at Anzali Lagoon in autumn 2005 and the species was identified and isolated using invert microscope. For culture of the rotifer, EPA medium was used together with freshwater chlorella sp. at 1*106 cells/ml density. Rotifers were produced as batch culture. Primary density of rotifers in 11 balloons was considered to be 30 ind/mL Results showed that the maximum density of rotifer reached 453±43 ind/mlin the seventh day and mean growth rate per day was 0.50. The average of the lorica length and width was 204 and 167 microns and the average of the egg length and width was 121 and 95 microns, respectively. This experiment indicated that freshwater rotifer attains suitable growth parameters in laboratory condition in a relatively short time. Also, we successfully determined the protocol for semi-intensive artificial production of the species.

The relationship between morphometric characteristics, motile spermatozoan percentage and sperm motility duration among male breeders of Rutilus frisii kutum in four different rivers (Shirud, Khoshkrud, Sefidrud and Chalevand) of the southwestern part of the Caspian Sea and water osmolarity, pH and temperature in four region of each river (estuary, river entrance to sea, artificial reproduction site and upstream) were considered. The mean motility duration time was 37.2±4.2, 41.4±3.9, 52.9±2.1 and 47.8±3.4 in the four rivers respectively. Also, the percentage of motile cells was found to be 49±4.1, 58.2±6.8, 74±4.8 and 68.1±5.9% for the rivers respectively. The mean osmolarity, temperature and pH were 71.7±66, 62.5±85.5, 40.2±34.2,36.7±34.4 mOsml/l, 14, 15, 13.6±0.2,14oC and 7.6±0.1, 7.2±0.1, 7.4±0.1 and 7.2±0.1 respectively. Our findings showed that there is a positive relationship between motile spermatozoan percentage and duration of motility. With the decrease in river water osmolarity from estuaries up to the river upstream, the motile spermatozoan. percentage and their duration increased. According to anadromous behaviour of the fish, with increasing distance from artificial breeding sites toward river upstream, quantity of spermatozoa and spermatozoan activity increased enhancing success in fertilization attempts.

We selected five sampling sites to identify Goby species in the southern Caspian Sea (Guilan province). Bottom trawling was used for the sampling from September 1999 to August 2000. Results showed that the Goby specimens in this area belong to the genus Neogobius and Benthophilus. Identification of the species was carried out by Dr. Coad of the Natural History Museum of Canada. Four species from the Neogobius were identified which were as follows: N. caspius, N.fluviatilis, N. melanostomus and N. kessleri. Two species from the genus Benthophilus were identified as B. stellatus and B. ctenolepidus., As for the biological characteristics of the N. caspius, we found that the average total length (TL) of N. caspius samples was 112.98±19.87mm and their average total weight (TW) was 16.39±6.21 grams. Age composition of the samples showed the fish were in age groups 1-3 years old with the two years old fish being dominant. Average absolute fecundity was 1031.91±598 eggs. Food items of the species based on the gut content were from Carididae, Mysidae, Cumacae, Hypaniula, Chironomidae, Nematoda, Abra, Gammaridae, Mytilaster, Bivalves and fish. Evidence of carnivore behavior was observed in some specimens. The most frequent food items were Cumacae, Abra, and Gammaridae respectively. The Cumacae was mostly observed in the gut of 1 and 2 years old specimens while Abra was observed mostly in the gut content of 3 years old specimens. Condition factor and feeding rate were highest in the 1 year old class. We found that with increase in fish age, these parameters declined. However, again at the age of 3, the parameters showed a slight increase. Relative gut length also increased from 0.97 in the age class 0+ to 1.38 in the age class 3+.

We launched a summer and winter cruise using two fishing vessels to assess the stocks of the sturgeon fish in the southern coasts of the Caspian Sea in the year 2004-2005. Eighty five random stations were selected and sampled using a 9 meter trawl in waters less than 10 meters and a 24.7 meter trawl for the depths above 10 meters. We caught 170 sturgeons in the summer cruise which comprised 142 Acipenser persicus, 19Acipenser stellatus, 4 Huso huso, 3 Acipenser nudiventris and 2 Acipenser guldenstadtti. In the winter cruise, 118 sturgeons were caught of which 75 were Acipenser persicus, 41 were Acipenser stellatus, 1 was Acipenser nudiventris and 1 was Acipenser guldenstadtti.
Catch per unit effort (CPUE) was calculated as 2 fish for summer cruise with the Acipenser persicus being the most abundant species with 1.67 individuals per trawling while for Acipenser stellatus this was 0.22. For Huso huso, the CPUE was 0.05 and for Acipenser nudiventris it was 0.04. For winter cruise, the CPUE was calculated as 1.38 fish, again with the Acipenser persicus as the most abundant with 0.88, while that of the Acipenser stellatus was 0.48. The CPUE for Acipenser guldenstadtti and Acipenser nudiventris was 0.01 in the winter cruise.

Pike (Esox lucius) of Chamkhaleh River in Langrood was studied from winter 2003 to autumn 2004. We collected 123 specimens of the fish and sent them live to the lab for examinations. Biometrical measurements, age and sex determination were conducted on the samples. The eye, skin, gill, digestive system, muscle and other organs of the specimens were examined for parasite infestation. Seven parasites: Raphidascaris acus, Cam, allanuslacustris, Diplostomum spathaceum, Tetraonchus monenteron, Triaenophorus Crassus, Corynosoma strumosoum, Lernaea sp. were found in the pikes of the Chamkhaleh River. The most prevalent parasite was R. acus (37.39%) and the least were C. strumosum and Lernaea sp. (0.81% each). The highest mean intensity of the parasites was related to T crassus (8.45 specimens) and the lowest was detected for Lernaea sp. (0.01). The highest range in parasite infection was seen for R. acus (1-45) and the lowest for Lernaea sp. with only one individual parasite. We observed seasonal, age and sex differences in infection rate with the parasites. This is the first time report of the pike as a host for C. strumosum.

Gills of catfish Silurus glanis (300g weight) of Mahabad Dam were examined for structural attributes in 2004. Immediately after catch, gills were removed and placed in Bouin and Glutaraldehyde for structural and microscopic examinations. For classical histological assessment, samples were stained with Hematoxylin and Eosin and examined under light microscope. For electron microscopy, cuts 90 nanometers each were prepared and stainted with Uranyl Acetate and Lead Citrate, covered with silver, examined and photographed.
We found the gill cells being composed of ionocyte a,b, accessory, mucous, pillar and mosaiccells. The ionocytes were located at the base of the gill rakers and intra-raker spaces. Thesestructural attributes of ionocyte cells demonstrate their active role in osmotic regulation of catfish.

In the years 2001 and 2002, two great floods occurred in the Madarsoo River in Golestan National Park, north-east of Iran. To study the effects of these floods, we assessed the age, growth and reproduction of Capoeta capoeta gracilis (Keyserlhng, 1861) in the river from November 2003 to December 2004. Fishes were caught by electroshocker and 1025 specimenswere randomly selected from the catch. Growth in length was expressed for both sexes with Von Bertalanffy equation. Growth parameters were estimated as L¥=249mm, K=0.22 per year and t0=-0.30 year for males and L¥=306mm, K=0.21 per year and 10=-0.38 year for females.
The length-weight relationships were described for males as ln W= -4.48 + 3.03 lnTL and as lnW= -4.59+3.0551 lnTL for females which shows a good feeding condition and a positive-isometric growth. Difference of length distribution between males and females is significant and males have lower lengths because this sex matures sooner so its growth is lower than females. Difference of fish length distribution between this study and previous studies on the c.capoeta gracilis of the river is significant and Lenkoran's length shows great decrease in this study as compared to previous studies. Age of the fishes ranged from 1+ to 5+ formales and 2+ to 8+ for females, the dominant age was 2+ and the mean age was calculated as 2.009±0.034.We found that C.c. gracilis population had become younger in this study, so we concluded that the floods had made great changes in age and length structure of the fish. Male to feplale ratio was 1.5±1.0 (P<0.01), the mean fecundity was 3116±l387 ova per female and maximum gonadosomatic index for both sexes occurred in June. We found no significant difference in the reproductive characteristics of the fish as compared with studies conducted before the floods.

Influence of phytase enzyme and replacement of fishmeal protein by soybean meal protein on growth and body composition of rainbow trout (Oncorhynchus mykiss) specimens each with a mean weight of 121.75±5.95 gwere studied. Experimental diets by factorial method 3 * 3, containingthree levels of replacement (0.0, 35 and 70%) and three levels of microbialphytase (0.0, 1000, 2000 units/kg diet) were formulated and prepared. Nine treatments and three replicates of random groups of 20 fish per each 2 cubic meter (2´2´0.5m) tank were used in the study. All diets contained 36-38% protein and about 4000 cal/g energy. During the 9 weeks period of the study, fish were fed to satiation level, three times daily. Statistical results indicated that the increase of replacement level to 35%had no significant effect on growth index (P2£0.05). Effect of replacement on body composition was not significant, except for crude energy which decreased in 70% level (p£0.05). Effect of phytase enzyme on growth index was positive and 2000 units/kg diet of phytase showed the best result (p£0.05), but phytase levels had no significant effect on body composition. Result also showed that there was a significant interactionbetween phytase enzyme and meal replacement (p£0.05). We suggest using 2000 units/kg diets of phytase with at least 35% replacement of fish meal protein by soybean meal protein as a suitable formula for growing rainbow trout.

Silver pomfert (Pampus argenteus) belongs to Stromatidae family and is considered an important commercial fish found in some major fishing grounds of the Hormozgan province waters. The stomach contents of 853 collected specimens were investigated from June 2001 to November 2002. The change in stomach content relative to the length classes and gonad stages, vacuity index, gastro-somatic index and frequency percentage of different food items were also studied. The diet consisted of a broad spectrum of food types, but crustaceans (especiallycopepods) were dominant. The next major food group was Bacillarlphyceae (16 genera), followed by Cyanophyceae (6 genera) and mollusks. Other major groups were Nematodeworms, Foraminifera and Dinophyceae (6 genera). Copepods were the primary and main food items with the Bacillarlophyceae being the second most important prey. Therelationship between stomach contents and maturity stages in females showed that the food take up increased during adult stages and then decreased during spawning periods. The vacuityindex (CV) was calculated as 14.49, indicating the voracity of Pampus argenteus. The gastro-somaticindex was estimated to be 4.5 based on monthly and maximum values during February.

The processing and comparison of quality of meat in farmed Acipenser persicus using two methods of dry and mix salting was carried out to provide a new formula for processing new sturgeon products. Ten fish specimens with a mean weight and length of 2 kilograms and 60cmthat were farmed for two years were used in this study. The meat of the specimens was processed using pure salt and a mixture of salt and one percent madder. Two replicates were used for each method. In the first method, dry sodium chloride was used at a rate of 250g of sodium chloride per kilogram body weight of fish (dry salting). In the second method, about 109 of madder was added to the 250g of sodium chloride (mix salting). Microbial examinations included total bacterial counts, Staphylococcus and Coli form bacteria assessment and chemical examinations included salt, protein and fat absorption, TVN, peroxide, and pH tests. Sensory tests as well as microbial and chemical experiments were carried out for the quality control of the processed samples for a period of three months. 
According to the results, Iranian National Standard and pure plate culture method (10-1,10-2 and 10-3) Coliform counts in the two different meat samples was lower than 10 per gram of meat. The total bacterial count and the Staphylococcus bacteria count was higher in the meat samples processed with dry salting. Besides, the rate of salt absorption and peroxide was lower in these samples. The protein, fat, pH and humidity were higher in the samples treated with dry salting. However, taste, flavor and color of the meat processed with a mixture of sodium chloride and madder was higher quality than that processed with dry sodium chloride. 
No significant differences were observed in chemical factors such as TVN and salt absorption for the two processing methods. This was also the case for microbial analysis including bacterial counts such as Staphylococcus and total bacterial count.

We studied production costs, factor costs and profitability of shrimp farming in the four southerncoastal provinces of Iran during the year 2000. A comprehensive questionnaire was used for data collection. A number of 144 farms were randomly selected, classified and analyzed. An expert team comprising an economist, statistician and shrimp aqua-culturist completed the questionnaire, while referring to all selected farms. Results showed that shrimp. larvae stocking density averaged 224966 per hectares and the shrimp production averaged 169kglha. On average, food, PL and labour costs per hectare were found to be Rials 10000, 6000 and 2000 respectively. In the year 2000, the average profit for the four provinces of shrimp farming was Rials 9555 per kg. of cultured shrimp. Hormozgan province had the highest profit with Rials 20092 per kg and Khouzestan province had the lowest with Rials 4576 perkg of the cultured shrimp.

To understand the change in fish consumption behavior of Tehran citizens, in the year 2005, an investigation was conducted using questionnaire. Using independent random method, 316 families covering all 22 districts of Tehran were selected. The results were combined with that acquired in the year 2001 to develop marketing programs. We used Fridman, K2 tests for nonparametric statistics and Z (normal distribution) and Phi Cramer index for analysis. The results showed that the quality and freshness of the products and the hygienic state of the distributing places had the highest effects on purchase. Also, the price and packaging had the same priority as in the year 2001. No significant relationship was found between income level of the families and their fish consuming tendency. Comparing the two years of study, we found that 16.6% more people preferred packed food in the year 2005 while per capita consumption had increased from 2.8 to 3.46kg.Withthe information on production date and health license already available on the products, the consumers demanded dietary contents. Considering the increase in marine fishery products, the families tended to consume more of the farmed aquatics with the live selling of rainbow trout being preferred the most. The behavior of consumers and their decisions to purchase fishery products in this period depended on production directions and economic development strategies which indicated positive aquaculture development programs in the country. We recommend continuing current policies regarding marketing factors. The results also showed that uncertainly about freshness and health of the products is the main reason for purchase from the representative fishery stores. The results shows more research and advertisement can improve awareness about packing advantages and its role in decreasing wastes and creating more added values.

We evaluated Zeolite efficiency in absorbtion of ammonia from sea water. Three phases including ammonia movement through Zeolite column, application of Zeolite powder and granule in closed containers filled with ammonia solution and dispersion of Zeolite in shrimp culture tanks were implemented in the study. For the first phase, ammonia solution in two concentrations (4.8 and 2.42mg/lit) and a water salinity of 42 ppt (sea water) was passed through the Zeolite column (400g of granule Clinoptilolite) in three replications.
Concentration of ammonia in outlet solution was between 0.2-5.4mg/lit in the first replication and 0.0 to 5.5, 0.0 to 2.6mg/lit in the 2nd and 3rd replication, respectively. At the second phase, volume and levels of ammonia concentration left in the closed jug of ammonia solution was different. The concentration of ammonia was measured at various time periods in four replications. The results showed that ion exchange in seawater is not a one way process, so that ammonia concentrations in the jugs with Zeolite fluctuated with time, contrary to its stable concentration in control treatments. At the third phase, Zeolite in granule and powder forms was added to culture tanks of shrimp juveniles (Penaeus indicus) weighting on average 0.2g each for 79 days of culture period and a stoking density of 16 individuals per square meter. Thus, we provided three treatments, using Zeolite granules, powder and one control. A Duncan's test of the growth and survival rate of the cultured shrimps showed no significant difference among the treatments (P>0.01).

Pikeperch (Sander lucioperca) is one of the economic fish species in the Caspian Sea, with no official report on its chromosome preparation and karyotype formula. For the metaphase preparation, 29 fry specimens of the fish weighting 10-25geach were used. Colchicine 0.01% at 0.7ml/100g of fish weight was injected in the muscular tissues. After 180 minutes, kidney and gill tissues were removed and hypotonized in KCL 0.075 M for 40 minutes, fixed with Carnoy mixture for 18-20 hours, homogenized and dropped on the slides, and stained with Giemsa 20% for 30 minutes. The prepared slides were swept by objective X100 light photomicroscope. The results showed that the chromosome number of this species is 2n = 48 and the chromosome arms is NF = 76. The karyotype formula of the species was found to be 2n = 1m + 13sm + 4st + 6a. Comparing the results of the study with those of other researchers showed that the Pikeperch chromosome number in the South Caspian Sea is similar to the fish in other parts of the world but the type of chromosomes and karyotype formula is different.

In this study, Freund's incomplete adjuvant (FIA) was used for emulsifying and sustained releasing of gonadotropin releasing hormone agonist (GnRHa) in Rainbow trout (Oncorhynchus mykiss).The hormone [D-Ala6,des GlylO] m GnRHa was diluted in 0.25 ml physiological saline and mixed with equal volume of FIA (GnRHa-FIA). A group of Rainbow trout brood stock were injected with GnRHa-FIA and compared with those receiving the treatment in two steps or one acute GnRHa injection. All of the fish that received GnRHa in emulsified form or in two steps injection ovulated in 10 and 11 days after injection respectively. In contrast, only 75% of the control fish and 60% of the fish with an acute injection ovulated up to 36 days after injection. Results showed that GnRHa-FIA injection as two steps injection protocol was effective in advancing the onset of ovulation, synchronizing the ovulation of treated fish relative to controlor acute GnRHa injected groups (P<0.05). GnRHa-FIA neither affected egg quality (P<0.05) nor did it cause any mortality in the treated fish.

A survey on the qanat fishes of the Markazi and Sirjan basins of Iran was carried out in the year 2001. Using electroshocker, cast net and river seine, we collected 767 specimens from73 qanats in the study area. We also measured pH, water temperature, air temperature, oxygen and other important attributes of the environment. The fish specimens belonged to 2 orders, 3 families and 3 species. Of the order Cypriniformes, the family Cyprinidae was present with one species Capoeta damascina (Valenciennes, 1849) and the family Balitoridae was represented with one species Nemachilus sargadensis (Nikolskii, 1900). Of the order Cyprinodontiformes, the family Poecilidae was represented with the species Gambusia affinis (Baird & Girard, 1853)

Persian Gulf is semi-closed water with high salinity and temperature and high evaporation rate and low water exchange with Oman Sea. Operation of oil wells in the area contributes to the water pollution in this intricate ecosystem. We selected nine stations in Shahid Rajaii harbour and one out of the area where samples of water and sediments were taken for assessment of density of total hydrocarbons and heavy metals using spectrophotometric (FTIR) and atomic absorption (AAS) methods, respectively. The results showed that in Shahid Rajaii harbour, the concentration of these pollutants are significantly higher than waters out of the harbour (P<0.05). Also, the correlation coefficients showed that the origin of mercury is different from other metals. Mercury has a biogenic origin, while other metals have lithogenic origin particularlyin Shahid Rajaii harbour.