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Japanese threadfin bream (Nemipterus japonicus) is one of the most important commercial species of fishes in the Persian Gulf. The purpose of this research was to elucidate some features of the sexual cycle and nutritional traits of fish caught in the Persian Gulf (Bushehr province) from September 2012 to September 2013. The total number of 315 fish was studied. The number of male and female fish was 101 and 184 respectively and the sex of 30 of them was not recognizable due to fish prematurity. Total length (TL) ranged from 20 to 36 cm with a mean (±SD) of 28.15±2.9 cm for females, whereas for males it ranged from 20.6 to 40 cm with a mean (±SD) of 31.48±4.1 cm. Moreover the minimum and maximum measured lengths were 20 cm (found in females) and 40 cm (found in males), respectively. The weight of female fish ranged from 98 to 303 g with a mean (±SD) of 172.06±3.8 g, whereas for males it ranged from 100 to 380 g with a mean (±SD) of 242.21±7.76 g. The average amounts of condition factor were 1.8±0.07 and 1.86±0.09 for males and females, respectively. The average amount of intestine relative length mean was 0.91 for all samples. Vacuity index was calculated in different months for evaluating the severity of feeding. The maximum and minimum amounts of filled stomachs were observed with 85% and 28.12% of filled stomachs in August and April, respectively. From 315 examined stomachs, 122 were empty and the others were full. The predominant food in the full stomachs was crab (56%) followed by fish (27%), shrimp (17 %), polycheat (8%), squid (4%), lobster (2%) and octopus (1%). The trend of GSI changes in females from February to April was upward and after that it became downward. Hepatosomatic index (HSI) fluctuations in males and females were similar to each other and conformed to GSI changes. The results showed that this fish was relatively gluttonous and crustacean was their main source of food, whereas fish and mollusks were their secondary source of food.
 
 

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Rainbow trout (Oncorhynchus mykiss) is an exotic fish in the inland waters of Iran and little is known about this species in Iranian natural waters. In this study, some biological characteristics of rainbow trout such as GSI and absolute and relative fecundity were examined in 355 specimens collected monthly from Beheshtabad River of Chaharmahal and Bakhtiari Province during April 2013 to March 2014. Total length of females and males ranged from 17.1 to 40.2 cm (26.05±4.54 SD) and from 15.5 to 40.3 cm (24.9±5.93), respectively. The age of male and female rainbow trout ranged between 1⁺ to 4⁺ and 2⁺ to 5⁺ years, respectively. The most frequent age groups were 1⁺ and 2⁺ in males and females, respectively. Sex ratio was 1M:1.3F. Based on macroscopic gonad observation, maturation cycle consisted of five stages; immature, developing, spawning, regressing and regeneration phases. The gonadosomatic index indicated that reproduction of rainbow trout in the Beheshtabad River occurred in October and Junary for males and in September and Jaunary for the females, with the highest  mean value of 3.28 and 4 in November and Jaunary for males and 4.22 and 3.48 in September and Jaunary for females. Oocyte diameters ranged from 0.125 to 3.5 mm. Absolute fecundity ranged between 680 and 3890 (1860±170) eggs. Relative fecundity ranged between 1900 and 9000 (4600±360) eggs/Kg body weight. It seems that this species has been able to adopt very well to the river conditions.
 

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In order to increase the knowledge of the probiotic effects on reproductive indices of fish, this study was conducted to investigate the effects of different levels­ of probiotic Lactobacillus plantarum on gonadal development and sexual maturation in zebrafish (Danio rerio). Some 720 zebrafish were fed the experimental diets in four treatments such as: 0%, 0.5%, 1.5% and 3% probiotic diets for 40 days. Based on the measurement of reproductive indices in this species, the maximum absolute fecundity was observed in the diet containing 3% probiotic, which was significantly different from the control treatment and the diet containing 0.5% probiotic. Based on relative fecundity index, the control treatment showed the lowest fecundity rate compared to the other treatments. The gonadosomatic index data showed the utmost gonadal index in the diet containing 3% probiotic compared to the other treatments, which was significantly higher than the control and 0.5% probiotic treated diets, but it did not show any significant difference with the diet fed 1.5% probiotic. Histological examination of gonads in males and females showed gonads development and complete sexual maturity in treatments fed 3% and 1.5% probiotic levels. The present study indicates that probiotic Lactobacillus plantarum at 3% level will have the best effect on reproductive and gonadal development parameters in zebrafish.  

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This study was carried out to investigate some reproductive traits of Periophthalmus waltoni in the coast of Sirik city. Overall, 496 samples were collected during a year that 291 samples (58.67%) were male and 205 samples (41.33) were female. The sex ratio (M/F) was calculated as 1.41:1 (p<0.05). The smallest captured fish was male (4.8 cm) and the largest captured fish was female (15.5 cm). Based on the results, the average total length and body weight of males were significantly more than females (p<0.05). The male and female showed negative allometric growth. Also, b value of the male (2.65) was more than the female (2.63) (p>0.05). Absolut fecundity and relative fecundity were counted as 5216±2098 and 368±136 eggs, respectively. The results showed a direct relationship between the egg number and total length. According to the results, spawning period was recorded from January to May with two peaks in April and January, which was associated with a maximum mean of total length in this time. On the other hand, the results showed that there is an inverse relationship between temperature and gonadosomatic index.

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In this study, some aspects of the reproductive biology of Caspian Roach caught by beach seining were investigated along the southeast coats of the Caspian Sea in the period of 2019-2021. From a total of 317 samples of caught fish (144 males and 173 females), the sex ratio of male to female was 1:1/2, which was not statistically significant with the expected ratio of 1:1 (p>0.05). The average fork length (± standard deviation) was 15.6 ± 2.63 cm (with a range of 10.6-25.5 cm) for males and 18.7 ± 3.70 cm (with a range of 11.3-32-5 cm) for females. The range and average weight for males were 18-214 g and 60.7 ± 36.20 g, respectively, and 22-502 g and 120.5 ± 74.76 g for females, respectively. The minimum, maximum, and average absolute fecundity of R. caspicus were estimated as 6707, 51438 and 18773 ± 9800 eggs, respectively. The mean relative fecundity was estimated to be 152 ± 33 eggs/g and 967 ± 367 eggs/cm in relation to the total weight and fork length, respectively. The absolute fecundity of the species increased with an increase in the length and weight of fish with coefficients of determination of R²= 0.62 and 0.68, respectively, so that the range of fecundity in the length range of 14.5-15.5 cm is equal to 6707-11807 eggs and in the length range of 27-32 cm was estimated as 35813-42693 eggs. According to the results, sexual maturity at stages IV and V is present in all sampling months for females of R. caspicus. The mean length (fork length) at first maturity (Lm50%) of females R. caspicus was 13.8 cm. The highest value of Gonadosomatic index (GSI) for males was observed in February with a value of 7.08, and for females in March with a value of 16.06 which decreased to 15.96 in April. Considering that the peak value of GSI and the high percentage of V maturity stage of R. caspicus is observed in March and April; it can be prohibited to catch this species in this time.