چكيده انگليسي :
in this research, the potential use of five hard parts (otolith, scale, eye lens, dorsal spine, vertebral bone) of Rutilus kutum for stocks discrimination and biomonitoring as well as their usability as biological archive in the southern Caspian Sea was investigated. Two soft tissues (muscle and liver) were also analyzed for assessment of the possible risk of consumption and use as biomonitoring tool, respectively. A total of 60 specimens were collected using beach seine from three sampling sites (adjacent to the estuaries of the rivers Sefidrud, Tajan and Grorganrud, respectively) in the Southern Caspian Sea in May 2016. In total, the levels of 13 major and trace elements in the samples (the seven soft and hard tissues) was measured using PIXE (Proton Induced X-ray Emission) and µ-PIXE methods.Generally, the pattern of elements occurrence in the eye lens was considerably different compared to the other hard parts. The orders of element occurrence in the two soft tissues were largely similar, but Sr was not detectable in muscle. Ca, Fe, S, Cl and K could be detected in all the selected tissues, while Br was detectable only in otolith.Minor similarities among the tissues were observed in the case of eye lens (for P, S and Zn) and liver (for Cl, Fe and K). Whereas, in the case of Sr and Ca, otolith shows the maximum distance. On the other side, in the case of K, the soft and hard parts could be categorized into two completely separate groups.Generally, vertebral bone and liver showed the highest and lowest number of the correlation pairs, respectively. In case of all the hard parts, very strong correlations were found between S and Cl. Among them, all the correlations, except for eye lens, were positive. There were no significant relationships between the elements and biological characteristics (weight, total length and standard length).Based on the results, it seems that all the studied hard parts, except for eye lens, may offer alternatives for biomonitoring of Ca, Cl, Fe, K and S in the southern Caspian Sea. The scales and spines represent a potential non-lethal alternative to the other hard parts. However, since fish physiology regulates the uptake and incorporation of some elements, it is not clear that levels of all of the mentioned elements reflect their variability in the environment. Considering Sr level in otolith, no significant differences could be found between the sampling sites 2 and 3. So it can be concluded that the specimens collected from the two sites are probably from the same population. Similar results were also obtained based on the results concerning K accumulation in scale. It can be concluded that scales may provide an alternative structure to otolith for stock discrimination of R. kutum in the southern Caspian Sea.Considering the µ-PIXE elemental distribution maps and their comparison with the annual growth increments on the five hard parts, no clear patterns could be detected. In other words, the used the method seems to be not sensitive enough to characterize of the elements concentrations based on the growth patterns. Therefore, the capability of other analytical methods (with higher resolution) in clear differentiation of the growth patterns should be evaluated in future investigations.Among the 10 elements that were detectable in the muscle using the PIXE method, only in the case of four of them (i.e. Zn, Cu, Fe and Mn) maximum allowable concentrations for human consumption have been defined, which in all the cases the mean concentrations in the present study were far below the recommended limits and accordingly it seems that in this regard there is no risk for human consumption of flesh of the fishes.
كليدواژه :
درياي خزر , ماهي سفيد , آرشيو زيستي , انگشت نگاري عنصري , ميكروپيكسي
