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The effects of environmental factors and season on agar extraction from Gracilaria corticata were investigated for the period 19931094 in the coastal areas of Persian Gulf. Water temperature, water salinity and ammonia and phosphate ions were measured monthly. Mean temperature was found to be 27.8 centigrade, mean salinity was 36.38 PPT., mean amonnia ions was 0.154mgi1 and mean phosphate ions was 0.029mgi1 . After harvesting, Gracilaria were dried and weighed and subjected to the alkali agar extraction method. Maximum and minimum agar yield were obtained in August and December with 10.01% and 5.44% respectively. There was a significant correlation between agar yield, biomass and ammonium fertility. Results showed that the maximum agar yield from Gracilaria was obtained in March and August......

Biological study on Gorganrood River was performed from November 1990 until October 1991. Fourteen sampling Stations along the 200km distance from Chai Qushan to estuary. Fish distribution was not similar in all parts and was more dense in lower parts. Density Of common carp, roach and white fish were more considerable particularly in spawning season. Density of benthic organism was very low and blood worms (Chironomidae) and shells of dead mollusca were obtained. Frequency of phytoplankton maximum in September and minimum in January. Bacilliarophyceae, Chlorophyceae and Mynophyceae had more biomass during studying period. Zooplankton had maximum biomass in September and minimum in February and March. Among zooplankton, Protozoa and Rotatoria had maximum biomass.

According to recognition and abundance of larve of commercial fish, caught during shrimp fishing season in eastern Chahbahar in the period of 7 to 27, November 1999, sampling was conducted from catch component during this time. Randome sampling was done 3 days a week for 3 weeks. Catch composition in this research divided to six groups, Osteal fish with 92.88% and Echinoidae with 0.12% has maximum and minimum frequency respectively. In catch composition 45 different marine species were identified and between commercial fish, 8 species were studied, but more study was done on Pampus argenteus, which has the most aboundance. It has the maximum frequencyin length 8 and 10cm. The minimum and maximum size of this species was 3 and and 19.5 cm, respectively. Besides this research was determined all commercial fish catched in larvale and juvenile stage.

In this study 401 specimens of Gattan (Barbus xanthopterus) caught by drifting and set gillnets, cast nets and forks were studied. Samples were collected monthly (October 1996 to September 1997) from Hamidieh Dam to Hour-Al-Azim Lagoon. Morphometric and meristic parameters and biological characteristics were studied in the laboratory. The Highest frequency of Gattan in the river was in March and in Hour-Al-Azim was in December. The length range of the fish in the river was broader than in the hour, and fishes with lengths more than 700mm were only observed in the river. Sharp decrease in GSI in May and occurence of spawning in May and June showed that reproduction of this species occurs in spring (in a two month period) and is relativery short. Minimum and maximum ova diameter were 0.01mm and 2.25mmin stages II and IV of gonad maturity respectively. An increasing trend in ova diameter up to April and decreasing in June showed one time spawning of this species. Surface water temperature in the spawning season was between 25.5oc and 28.65oc and turbidity was in its lowest level in this period. Sex maturation in males occurred in length of 151-200mm (one year old), and in females in 501-550mm (3 years old). Average sex ratio (male to female) was 1:1.31 which is not significantly different from 1:1 (95% confidence limit).

Otolithes luber is one of the valuable commercial fishes in thc South coasts of Iran and has been classified at the top level of commercial categorisation, so owing to its economic importance, its biological charactristics were studied in Sistan & Baluchestan coasts in 1995. Three landing called Pozm, Bris and Remin were choosen for commercial catch sampling in this respect and I I I male fish and 149 female ones were outopside within 7 months 01' evaluation. In feeding evaluation through numerical method, Squilla with 42.8% and Engraulidae with 1.4% consisted maximum and minimum percent of male fish stomach contents, respectively, and for female maximum and Illiniruum percent of stomach contents were unidentified bony fishes with 35.7% and polynemidae family with 7%. The results showed that male fishes mature prior tofemales as they are smaller than females and no importante difference was seen in sexual ratios in various month except March. Spawning was from December to the end of April and an outstanding spawning surge was observed from March to April. However, there was a light surge in November. The least coefficients of fatness in terms of male and female were 0.9 and 1 in April respectively and the most ones were 1.33 for male and 1.20 for female in Januray.

In September 1990 during a 19 days study, Mugil sp was cought in Babolsar fishing area to determine various ovulation phases. It was found that up to day 7 from study onset, nearly 60 percent of the fishes were in the 4th gravidity phase after which the fishes in the 5th gravidity phase were dominant in the catch prolonging up to day 15. Concurrently, the fishes in the 4th gravidity phase decreased. From day 15th on, spawned fishes showed a maximum along with a decreased percent of fishes in the 4th and 5th gravidity phases. The results of this study can be usefully employed in the management of fishing of the species......