جستجوی مقالات مرتبط با کلیدواژه « حوضه جنوبی دریای خزر » در نشریات گروه « محیط زیست »

This study was designed to determine the probable effect of rainbow trout cage culture on the biodiversity indicators in the Abbas Abad area, southern basin of the Caspian Sea. For this purpose, biological samples (benthic macro invertebrates, phytoplankton and zooplankton) were collected at distance of 5, 50, 100 and 1000 m from the cages in December 2014 (before the culture period), March and April (production period) and August 2015 (after the culture period). In this study, 9 taxa of benthic macro invertebrates (with the dominance of polychaetes; Streblospio gynobranchiata and Hypaniola kowalewskii) and 42 species of phytoplankton belonging to five phyla (with the dominance of Bacillariophyta) were identified. A total of 10 taxa of zooplanktons were identified with the copepod; Acartia tonsa being the dominant taxa as well. The results showed that the distribution and abundance of biological community were significantly affected by the seasons (p < 0.05) where as it was not affected by the distance from the cages (P>0.05) and in most cases, changes of biodiversity indicators were not affected by cage culture activity. It seems that the rainbow trout cage culture in the Abbas Abad region no remarkable effect on the biodiversity indicators in the vicinity of small scale fish cages due to short duration of cage culture and strong water currents, so that observed changes were more associated with seasonal fluctuant.

Habitat loss is one of the most serious threats to the recovery of fish stocks and can jeopardize the ability of marine coastal areas to support artisanal fisheries. On the other hand, habitat species modeling is a practicable solution for conservation and protection of marine ecosystems and habitats. In the present study, species suitability modeling was applied to determine habitat of Caspian kutum in southern Caspian Sea that five environmental variables include depth, chlorophyll a, photosynthetically active radiation, sea level anomaly and sea surface temperature were used. The results show that the most habitat suitability of Caspian kutum was in southwest Caspian Sea (include 8c, 25 and 15b indices) and depth and chlorophyll a are the most important environmental variables for the Caspian kutum to modeling its habitats. The results of accuracy assessment for weighted scenarios show that best scenario considering the AUC ROCs of 0.69. According to suggests that output of present study used a criteria for identifying marine protected areas, site selection of aquaculture and others Ecosystem Services Models in southern Caspian Sea.

In the present study the morphologic traits of Leuciscus orientalis (Nordmann, 1840) populations were examined in the Doogh River, Siahroud River and the Sefidroud River in the Southern Caspian Sea basin. A total of 190 fish specimens were collected and 25 morphometrics, 5 proportional morphometrics and 9 meristic characters were recorded. Existence of sexual dimorphism was confirmed in all populations by t test analysis on morphometric features. Pupil diameter, postdorsal distance, length of anal fin base, interorbital distance and head width were significant different between male and female specimens (p<0.05). Despite of similar meristic characters among populations, Doogh population has more connection to Siahroud population based on taxonomic distance of morphometric traits rather than Sefidroud population. PCA revealed that first and second componants cause 69.77% of total variance of differences. In order to show clear relation of populations CVA/MANOVA analysis has been applied. The results showed that all populations separate significantly (Wilk̍s lambda= 0.052, p<0.05), first and second canonical includes 66.8% of total variance. Coudal peduncle width, pectoral fin base and eye diameter were loaded on first canonical and inter-orbital distance, pupil diameter and length of anal fine base were loade on second canonical.