The study of some biological characteristics of Pipe fish Syngnathus caspius Eichwald, 1831 in the Caspian Sea (Gorgan Bay)

So far, the Caspian black-striped pipefish (S. caspius) is the only recorded species of the Syngnathidae in Caspian Sea. In this research, 50 specimens of pipefish were collected from brackish water of Gorgan Bay, and the basic information related to 21 morphometric and 6 meristic characteristics and population dynamic parameters including L-infinity, t-zero , instant growth rate, and condition factor were estimated. Results show the existence of two distinct populations with significant differences in some morphological parameters, especially in eye diameter, snout length, anal and pectoral fins height and mouth height in pipefish inhabiting southeast Caspian Sea. However, there was no significant difference between the two populations in meristic characteristics. Aging using opercula revealed 5 age groups (0+4). The maximum total length was observed 144 cm (3 years) and 149 cm (4 years) in male and female genus, respectively. Von Bertalanffy model was Lt=177.94 (1-e0.3(t.56)) and Lt=153.69 (1-e0.3(t.07)) for Caspian population and semi-Black Sea population, respectively. Growth pattern was reported as negative allometric model in two populations. Separation of the studied populations in Gorgan Bay were proved via investigating some biometric parameters of Caspian pipefish using multivariate statistical methods of PCA and DFA. Final identification of species or subspecies needs genetic studies.
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