مجله علمی شیلات ایران
سال یازدهم شماره 2 (پیاپی 39، تابستان 1381)

This project was conducted to determine the effect of Pseudomonas fluorescence bacteria on increasing the growth rates of some species of algae namely Chaetoceros Sp. , Skeletonema sp. , Tetraselmis sp. , Chlorella sp.  
In this order, the mentioned bacteria were extracted by separator and Zobell 16E media from prawn broodstock ponds, then purified and mass cultured. The algae selected mass, were cultured in Conway media and then these bacteria were investigated at the blooming phase in the several experiments of various treatments in combined culture method. The results revealed that the mentioned bacteria could apply as a partial substitution body of aglae media and it could be used as a new media in various percentages. The results indicated, the very positive effect of bacteria on cultured algae. Therefore, Pseudomonas fluorescense can be used in algae cultured in 50-150 mglit density as a new method for algae culture. This bacterium Could be a new media for Chaetoceros sp. , and Tetraselmis sp. , but for Skeletonema sp. , other percentages of media should be used.

The reproduction biology of A. sexfasciatus, one of the main and important ornamental fishes in the Persian Gulfwere studied during 1997-98.  
For sampling, Larak island sited on south-eastern of Bandar-Abbas was chosen. The main fishing gear was hook for collecting samples. During this investigation, weight, length (FL & T. L), GSI, HSI, Kf, sex ratio, LM50 and sexual overlap zone were measured or calculated. Also, the histological studies were done on gonads. The results showed that this species is a protogenous hermaphrodite. A. sexfasciatus has an allometric growth and the results of GSI, HSI and Kf indicated that the spawning season occured in spring as a total spawner species. The sex ratio was found M: F=1. 00:1. 24 without any significant difference. The overlap zone was recongnized 30mm (with a range of 125-155mm). The LM50 was calculated 130-140mm for females and 160-170mm for males. The size at first maturity for females and males were determined 105 and 120mm, respectively.

This research project was carried out in Gulian Fisheries Research Center in 1998. For this purpose, two ponds were selected: Pond No. 1 with 450m2 area and pond No. 2 with 250m2 area and then 3500 pieces/hectar of hybrids with 5-7g weight were added to the ponds.  
In order to determine their main food, they were fed by pelletes and grass according to their mean weight. Meanwhile, by adding mineral and organic fertilizers to the water, a suitable media including phytoplanktons, zooplanktons and benthoses were prepared for feeding of fishes.  
The stomach contents observations of 160 specimen of hybrids showed that this hybrid is a herbivorous fish and macrophytes were their main diet; and phytoplanktons could be considered as the secondary random food.

The indian white prawn (Penaeus indicus), as one of the commercially important and dominant species along the East coast of Hormozgan province, is a very potential and prospective candidate species for shrimp farming. Since, there wasn't well enough information about biology of this species from Iranian wateres, therefore. some biological aspects such as growth rate, reproduction behaviour distribution pattern and feeding habits were studied from March 1997 to March 1998.  
Monthly sampling were carried out from the fishing grounds and estuaries of Jask area in the Oman Sea by small trawlers and beach seines gears. Initial growth 01 male was faster than female, with calculated K=l. 5 for male and K=1. 3 for female. Isometric growth trend was observed in both sexes. Sexual maturity attained within the first 12 months. Spawners were occured abundantly during post-winter, spring and beginning of summer. Postlarvae and sub-adults were found in the esturies with 25-100 mm length, and high densities were observed around the mangrove's roots. They spend at least 3 to 5 months of their life span in the esturies. Analysis of stomach contents revealed that this species is an omnivore with indicative contents of detritus, polychaetes, crustaceane, bivalves, algae and sand particles, with preponderance of vegetable constituents in the sub-adults and of detritus in adults.

 The bivalvia of Abra ovata belongs to SEMELIDAE family inhabits in Black Sea and Azov Sea; and was introduced to the Caspian Sea in 1939. This species has a significant role on sturgeons' feeding.  
384 specimen of this species were studid to determine the growth rate and age composition. The results indicated that the mean length of this bivalve was measured 9. 33±2. 26 mm with minimum and maximum length of 3. 40 and 15. 0mm, respectively. There was found a significant difference between the samples of two different depths of 10 and 20m. The dominant length groups for different seasons were as follow:  
spring: 3-5mm, summer: 5-7mm, autumn and winter: 9-11mm.  
By using Bhattacharya method, 3 individual Cohorts was determined. The length- weight relationship was W=0. 0008L2. 97  (R2=88. 35, n=383). This species has an allometric growth and the Von- Bertalanfy growth equation was calculated L (t) = 14. 5 [1 - exp-1. 5  (t + 1. 89) ].  
The natural mortality coefficient and relative condition factor were estimated 1. 56 per year and 1. 053, respectively.

In this study some cysts of Artemia were collected from Incheh lake in Golestan province and then were incubated to obtain nauplii.
These hatched nauplii were fed by Chlorella sp., and synechococcus sp., in three different treatments and three replicates with densities of 20, 40 and 60 specimen/lit and were reared up to adult stage. The period of rearing for above mentioned densities of two different algae were 15, 17 and 20 days; and in 16, 19 and, 23 days respectively.
The average fecundity and mean length of Artemia fed on Chlorella sp. were 83.E 69.8 and 34.5 cysts/individual and 104, 10.1, and 9.1mm length; and for the Artemia fed on Synechococcus sp. were 54.1, 36.8 and 19.3, cysts per individual and 10.0, 9.0 and 8.8mm length, respectively. There were significant difference in growth rate and fecundity among the traetments of each group of Artemia (P<0.05).

During a protozoological study on the fishes of West-Azarbayejan province (Northwest of Iran) in 1998, three different protozoans were revealed. Myxobolus musayevi from Capoeta capoeta, Myxobolus dispar from Aspius aspius taeniatus and Goussia carpelli from Cyprinus carpio.  
Altogether 13 different fish specimen were examined. The fishes including: Aspius aspius taeniatus (2), Rutilus ruti/us (3), Capoeta cpoeta (2) and Cyprinus carpio (6). They were caugth from Aras and Mahabad Dams and transported alive to the laboratory where they were wieghted and measured. Then, they were examined for protozoan infections when their spinal cord was cut.  
Myxobolus musayevi had already reported from Capoeta capoeta from Taj an in Mazandaran province. This is the first record of Myxobolus dispar from Aspius aspius taeniatus from Iranian freshwaters. Goussia carpelli also had already recorded (unpublished) from the Cyprinus carpio from Sepeedroud River in Guilan province.  
In this study, three of C. carpio which were caught from Aras Dam had been infected by the oocyst of the Goussia carpelli in the mocus of the intestine.