Feeding habits of yellow fin tuna were studied in the Oman Sea in 1998-99. 546 stomach contents with fork length frequency 38-173 cm were studied and classified as full, semifull and empty. Occurance of empty stomachs were high (63.10%) in males and 59.37% in females) in the specimens which indicated daily feeding of yellowfin tuna. Purpleback flying squid (Sthenoteuthis oualaniensis) was the most dominant prey species observed in this study (60% in males and 57% in females), occurance of teleost fishes were found to be the second (38% in males and 42% in females). Furthermore, crabs were also identified as a part of stomach contents with a low frequency (1-2%).

Some aspects of reproductive biology of yellowfin Seabream, Acanthopagrus latus, in coastal waters of Bushehr was investigated from Mar-Apr 1997 to Mar-Apr 1998 (1 year). Sampling was conducted monthly and a total of 182 samples were examined to determine sex, sex ratio, gonad weight, gonadal maturation index, fecundity, and also length weight relationship. According to result, average sex ratio (male to female) was 1:1. Spawning peak was found to occur in Jan-Feb. The average absolute fecundity was 1842700, and was found to have correlation with length-weight relationship.

In the present research which was done during the period of July 1997 to June 1998, histological studies on maturation stages of 40 yellowfin tuna specimen (Thunnus albacares) were conducted.It was concluded that the ovaries of this fish had the following characteristics; Germination disk were not persent. There were no difference among anterior, posterior and middle parts of maturity stage of ovaries. All observed ovaries were asynchronous. The ovaries had five maturity stages which were as follow:a) Immature      b) maturing       c) Rippening      d) Ripe             e) SpentAvarage dimension of oocyte in different stage are as follow: Immature (<20µ); maturing (>40µ); Rippening (<60µ) and Ripe (<120µ).

In this research, five species of genus Polystichum, belong to Aspidiaceae, namely, P. lonchitis, P. woronowii, P. setiferum, P. braunii and P. aculeatum, gathered from Gilan and Mazandaran Provinces were anatomically studied. To distinguish anatomical character of different growing organs such as pinnules, rachis, rhizumes and roots, the cross section was prepared. Based on these researches, identification key was made and the results were shown with most differences in shape and size of xylem in rachis sections.

In recent years significant losses in mariculture have occurred due to parasitic infections such as Lepeophtheirus sp. and Caligus sp. The parasitic investigations are mainly restricted to salmonid hosts although it was found to be problematic in other cultured marine fish species. Acanthopagrus latus and Acanthopagrus bifasciatus are two commercially important fishes of Persian Gulf and Oman Sea and there is an intention to be used as cultured species in Persian Gulf. Despite the importance of these fishes, there is no comprehensive report about parasitic fauna of these fishes. The aim of this study was to determine the prevalence of infestation of these two fishes to metazoan parasites. For this purpose, 40 fresh, dead individuals of Acanthopagrus latus and also 40 individuals of Aconthopagrus bifasciatus were caught from Ahvaz fish market from October 2005 to May 2006. After the initial biometry, different organs of fishes were examined for parasitic helminthes and arthropods by standard parasitological methods. According to the obtained results, Acanthopagrus bifasciatus had higher prevalence of helminthes infestation (97.5%). The prevalences of trematoda, nematoda and crustaceans infestation in this fish were 95%, 55% and 32.5% respectively. The parasites that have been recognized in this fish species were: trematoda, including Polylabroides sp., Lamel/odiscus sp., Syncolium sp., Asymphylodora sp.; nematoda, including Capillospirura sp., Capillaria sp., Contoracaecam sp., Gnathostoma sp., Raphidascaris sp., and crustaceans including Caligzts sp. And Lepeophtherius sp. The prevalences of trematoda, nematoda and crustaceans in Acanthopagrus latus were 37.5%, 45% and 55% respectively. The parasites that have been recognized in this fish species were: trematoda, including Polylabroides sp. and Asymphylodora sp.; nematode, including Contoracaecam sp., Gnathostoma sp., Anisakis sp. larvae, and crustaceans, including Caligus sp., Lepeophtherius sp. and Actheres sp.

Embryonic and larval development stages of yellow fin seabream (Acanthopagrus latus) were studied in two average temperatures (21 and 24°C) in Marine Fish Research Center in Emam Khomeini Port. Egg diameter in initiation of fertilization was 739.35±0.0081m and during final hatching it was 792.36±0.0095m. The average egg diameter from fertilization until final hatching was 763.49±0.0016m. The average egg diameter was 751.81±0.0064m inmurola stage, 767.55±0.0074m in nurula stage, 779.97±0.0084m in appearance of heart stage and 780.84±0.0086 in the increasing of pigmentation stage. Duration of egg incubation and embryo development of yellow fin seabream (Acanthopagrus latus) was 31 hours and 15 minutes at 20±1oC and 26 hours and 15 minutes at 23±1oC. In this study, 20 stages of embryo development of yellow fin seabream were identified through incubation period from fertilization to final hatching.It seems that water temperature can be an effective environmental factor in the fish embryo development, so that hatching at 20±1oC occurred in 5 hours later than when at 20±1oC. Temperature change had no effect on the number of larvae and characteristics of embryo development. The information gathered through this study is useful when planning for artificial reproduction of this commercial species and can improve the propagation process.

We examined the possibility of replacement of the live food (rotifer) with a vmicroencapsulated diet (MED) from first feeding in yellow fin seabream larvae by utilizing compound feeding technique during the first two weeks of larval life. The experiment consisted of five treatments and a control group (100% rotifer), which was fed live food during experimental period (regime A), three experimental treatments which received MED supplementing with reduced rations of rotifer including 75, 50 and 25 percent of rotifer in the control treatment (regimes B, C and D, respectively), and finally a treatment received exclusively MED throughout the experiment (regime E). At the end of the experiment results indicated that the regimes A, Band C did not differ significantly for total lengths, final survival and stress test resistance (P>0.05). In terms of dry weight, there was no significant difference between 100% live food treatment (A) and that received 75% live food in control treatment (B) (P>0.05). The solely MED treatment showed significantly lower growth and survival than other treatments receiving rotifer (P<0.05). The results revealed that complete replacement of live food with MED are still not possible in Acanthopagrus lotus larval rearing. Nevertheless, a substantial 50% reduction in the daily supply of live food can be achieved with a combination of microencapsulated diet and live food.

This study was carried out to investigate the specific activity of amylase, protease and lipase, as a selective criterion of probiotics, in some Bacillus sp. and Lactobacillus sp. isolated from intestinal tract of yellowfin seabream, Acanthopagrus latus. The results showed that all seven Bacillus and three Lactobacillus isolates were able to produce enzymes, although the specific enzyme activity was significantly different between the isolates. The specific activity of enzymes was higher in Bacillus isolates than in Lactobacillus isolates. Maximum and minimum activity of protease was observed in Bacillus BP5 isolates (3.13 IU/mg protein) and Lactobacillus LP1 isolate (1.03 IU/mg protein) respectively (P<0.05). Highest and lowest amylase activity was observed in Bacillus BP6 (3.00 IU/mg protein) and Lactobacillus LP2 (0.04IU/mg protein) respectively. Bacillus BP6 (1.40 IU/mg protein) had maximum lipase activity and was significantly different from other isolates (P<0.05).