Psettodes erumei is the sole fish species belonging to Psettodidae family that lives in the Oman Sea. The species has a flat body and is thicker than other flat fishes. It has a large mouth with strong teeth and gray-brown color on body surface; and is mostly found in muddy-sandy substrates up to 25m depths. The species is carnivorous and feeds on prey fishes. The common trawl and gillnet are commonly used for catching the fish. This study was carried out in the Oman Sea in 2002 covering 86 trawling stations. After each haul, the trawl was emptied on board for separation, identification and weight measurement of the catch items. The CPUA was calculated by Swept Area method and used as an index for distribution analysis of the fish species. The maximum snout-length was found to be 66cm for the study area and the length-weight relationship was calculated as W= 0.0294 TL 2.7973

In this study, Total number of 181 Rudd (75 male and 106 female) using gill net were caught in the Anzali wetland from April 2008 to March 2009. Fishes were measured using biometry board and caliper. To measure fork length of small samples, it was utilized regular or digital calipers and digital scale with precision 0.01 g was used to weight samples. The age range of samples was between 0+ to 2+ years. SPSS, One Way ANOVA and regression were used to analyze data and Excel was utilized to draw curves. Average fork length and weight of samples were determined 133.99±20.5 mm and 46.02±23.4 g, respectively. Tukey's test showed significant difference in fork length in both sexes. The fork length-total weight relationship and correlations were determined W=0.0000087 FL3.145 and r2=96% respectively.Regression equation in male was W=0.00000979 FL3.119 with r2=97.2% while in females, it was W=0.00000655 FL3.205 with r2=94.1%.

The freshwater spiny eel, Macrognathus pancalus is an inland water teleost fish commonly known as barred or striped spiny eel found in Asia. The sampling areas were selected which are spatially and geographically different and characterized by different environmental conditions in order to elucidation of ecotype. A total 345 specimens were collected from the sampling sites during January 2008 to December 2010. The weight of M. pancalus in the present study nearly the cube of its length in all cases as the values of regression coefficient „b‟ were found to be close to 3. The length weight relationship indicated the isometric growth in all the samples of striped spiny eel collected from different environmental condition. The coefficient of regression „b‟ were more in the riverine population (3.17±0.08) as compared to the populations of a large lake i.e. Beel (2.85±0.13). The coefficient of determination, (r2) in all the cases was highly significant (p<0.001). The relative condition factor (Kn) were also calculated and the average of condition factor in riverine and beel populations of spiny eel were found to be 0.50±0.09, and 0.47±0.05, respectively. The length-length relationship was highly correlated (r2= 0.99 at P<0.0001) for all the individuals of both habitats. A significant size difference was also noted between the river basin populations of M.pancalus. In the present study the length-weight, length-length relationship of M.pancalus in two different river basins was compared.

The age and growth parameters of the brond-snout, Chondrostoma regium in Beheshtabad River of Chaharmahal & Bakhtiari Province were investigated during April 2013 to April 2014. The males ranged between 8. 04-22. 10cm and 5. 20-105. 00g. The females ranged between 7. 84-23. 15cm and 8. 70-155. 00g. Males were categorized in age classes 1+-5+ and females in age classes 1+-6+. The age class 3+ was the dominant one in the whole samples. The length-weight relationship for males, females and all individuals was as W=0. 0089L3. 045 (r2=0. 95), W=0. 0082L3. 109 (r2=0. 85) and W=0. 0107L3. 000 (r2=0. 92), respectively, indicating a positive allometric growth pattern for the females and an isometric growth for the males and all fish. The age-length and age-weight relationships in males and females were estimated as Lt=26. 23[1-e-0. 267(t+0. 483)], Wt=160. 77[1-e-0. 267(t+0. 483)]3. 045 and Lt=31. 89[1-e-0. 148(t+2. 067)], Wt=266. 11[1-e-0. 148(t+2. 067)]3. 109, respectively. The growth performance index (Ф ') value was 3. 84 in males and 2. 18 in females, indicating a faster growth rate in males. The mean condition factor was 1. 02± 0. 01 for males and 1. 14± 0. 02 for females. The relative length of gut was 1. 18± 0. 05 for all fish, indicating a herbivorous habit for this fish. The highest mean feeding intensity of males was in July and the lowest in March and April. In the female, the highest was in January and the lowest in June. The highest mean value of Gut vacuity index of males and females was in the spring and the lowest in summer. About 55% of the studied stomachs were full. The highest number of empty stomachs was in May (80%) and the lowest in July (32%). Based on the mean Gut vacuity index (48%), this fish is considered a medium feeding fish (40

The length-length (LLRs), length-weight (LWR) relationships and relative condition factor (Kn) of 505 specimens of pike, (Esox lucius Linnaeus, 1798) from Anzali Wetland, southwest of the Caspian Sea, were studied from April 2012 through March 2013. The length-length relationships among total length (TL), fork length (FL) and standard length (SL) for pike were found to be highly significant (r2>0.986, P<0.001).The values of b in length-weight relationship in males (3.1495), females (3.1843) and for all specimens (3.2137) indicated isometric growth. Mean relative condition factor for male, female and all specimens were 1.003, 1.004 and 1.008 respectively. The result of LWR could be used for fishery managers to approve appropriate regulations for sustainable fishery management. Few studies have been conducted on these parameters of pike and this is the first report on LLRs, LWR and Kn of pike from Iranian waters.

This study aimed to achieve length frequency, condition factor and length-weight relationship of the rock oyster, Saccostrea cucullata in the coastal waters of Persian Gulf. Sampling was carried out by 0. 25 m2 quadrat through intertidal zone from winter 2015 to autumn 2016. According to the results, length-weight relationship calculated as W=0. 000004L2. 79 for both sexes. In addition, coefficient of determination (R2) value was determined as 0. 94. Furthermore, b value was significantly different from 3. Condition factor was estimated as 14. 36, 16. 87, 20. 85 and 20. 76 for autumn, winter, spring and summer, respectively. Mean length and weight were 34. 4± 4. 96, 36. 8± 8. 46, 30. 25± 7. 1 and 33. 31± 4. 31 cm and 8. 9± 7. 57, 10. 4± 9. 8, 10. 9± 6. 11 and 7. 8± 4. 19 g in spring, summer, autumn and winter, respectively. Maximum and minimum length were 97mm and 2 mm in spring and autumn, respectively. Maximum dry weight was found in winter (2. 21g) and the minimum was determined in autumn (0. 009 g). Maximum length frequency was observed in the 35-45 mm range class in all seasons. However, range class of 40-45 mm was also frequent in the spring. According to the nMDS results based on length and weight ordination, autumn was distinct from all seasons probably due to the juvenile recruitments in this season.

In order to investigation of growth pattern and body weight-length relationship of narrow clawed crayfish, Astacus leptodactylus in different stages of its life, approximately 10000 newborn crayfish were released in earthen pond. This pond had the similar condition to their habitat. Sampling was done during four stages of their life, under 2 months and 4, 6, 15 months among crayfish population. After separating the samples as sexes, some indices such as total length, total weight, claw weight and abdomen meat weight were measured. The results of this study showed, there is a power relation between length and weight indices in different parts of crayfish body for male and female. The growth pattern in experimental crayfish was isometric while the claw growth pattern was observed as allometric in male according to this relationships and regressions analysis.

This research was conducted to study length frequency distribution, length-weight relationship (LWR) and condition factor of 10 cichlid fishes, viz. Coptodon guineensis, Coptodon zillii, Coptodon dageti, Pelmatolapia mariae, Hemichromis fasciatus, Pelvicachromis taeniatus, Chomidotilapia guntheri, Tylochromis sudanensis, Sarotherodon galilaeus and Sarotherodon melanotheron from New Calabar River. Samples were collected on monthly basis during February to July, 2017. A total of 1073 specimens ranging from 13. 12± 0. 82 to 17. 07± 0. 94cm in total length and 45. 00± 8. 00 to 103. 01± 25. 81g in total weight were collected. The LWR regressions showed that the exponent b value ranged from 2. 38 (Coptodon guineensis) to 3. 00 (Sarotherodon galilaeus). The coefficients of determination (r2) of the LWR regressions ranged between 0. 82 for Coptodon guineensis and 0. 98 for Sarotherodon galilaeus indicating strong LWR relationships. The Fulton condition factor ranged from 1. 95± 0. 06 (Pelvicachromis taeniatus) to 2. 22± 0. 11 (Pelmatolapia mariae), indicating good conditions for the studied species.