The size frequency distribution for age structure, lengthweight (LWR) and length-length (LLR) relationships of six populations of Platycephalus indicus along the Persian Gulf coastal waters in Iran are reported. A total of 180 P. indicus specimens were studied from six localities including Charak, Bandar-Abbas, Shif, Motaf, Khur-Musa and Bahrekan. The maximum standard length recorded for the studied populations ranged between 300 to 510 mm and the b values of the length-weight relationships ranged between 3.0 and 3.2. The obtained results indicated isometric growth patterns for all these populations with the exception of the Bahrekan population which showed a positive allometric growth pattern. The LLR between the total and standard lengths in these populations were found to be highly significant. The results would be useful for further studies on population assessment and sustainable conservation of the fish along the Persian Gulf coastal waters.

Background: Morphological studies on fishes are important from various viewpoints. Studies carried out on the Caspian Sea fishes show that many species possess speciation and population formation microprocess running. Morphological characteristics of the native endangered Caspian lamprey, Caspiomyzon wagneri Kessler 1870, from migrating stocks of two major rivers in the southern Caspian Sea were analyzed to investigate the hypothesis population structure and morphologic sexual dimorphism. Results: Univariate analysis of variance of 180 adult specimens showed significant differences between the means of the two studied groups for 15 standardized morphometric measurements out of 31 (P < 0.05). In morphometric trait linear discriminant function analysis, the overall assignments of individuals into their original groups in male and female specimens were 77.1 and 84.0 %, respectively. The discriminant analysis showed a morphological segregation of the studied populations based on the characters predorsal length, interdorsal, interorbital distance, tail length, and first dorsal fin length. The principal component analysis, scatter plot of individual component score between PC1 and PC2, showed the specimens grouped into two areas but with high and moderate overlap between two localities in males and females, respectively. Conclusions: The present study indicated that there are at least two types of morphological forms of Caspian lamprey that had high morphometric differentiation in the rivers across the southern Caspian Sea, which can be considered in conservational policy of this valuable species.

Summary Length–weight (LWR) and length–length (LLR) relationships were estimated for four shad species of the genus Alosa, reported from along the southern Caspian Sea coast, north of Iran in a study from March 2014. Two of these species are endemic to the Caspian Sea. The length–weight parameter b for these species ranged from 2.99 to 3.24, with regression coefficients (r2) ranging from 0.91 to 0.99. All LLRs were highly significant (r2 > 0.96).

Summary The present study describes the length–weight relationships (LWRs) and condition factors (K) of Alburnoides samiii and Ponticola iranicus in the Sefidroud River from the southern Caspian Sea basin, September 2013 to August 2014. This study presents the first known reference in the FishBase database regarding the LWRs and condition factors for these two indigenous species.

Summary The present study provides the length–weight (LW) and length–length (LL) relationships for two goby species, Neogobius caspius and Proterorhinus nasalis, which were captured in the southern Caspian Sea. Total length (TL) and standard length (SL) were determined as well as weight. Specimens were collected monthly from September 2014 to August 2015 by beach seine (mesh size 10 mm). The LW parameter b for these species was 3.17 and 2.99, respectively, with a high coefficient of determination (r2 > .95). All LLRs were highly correlated (r2 > .97). Both species had no previous LWR and LLR estimates in FishBase.