فهرست مطالب r. pourgholam

A new non-native ctenophore species, Beroe ovata, was recorded for the first time in the southern Caspian Sea on 13 November 2019 during a regular plankton sampling program. Considerable aggregations (1-5 individuals/m3) of B. ovata were found near an aquaculture site for fish cage, about 8.5 km offshore. The arrival of B. ovata, a non-native ctenophore predator for the Caspian Sea, has been much anticipated since the arrival of its prey, another aggressive ctenophore Mnemiopsis leidyi in the late 1990’s. The adverse impact of M. leidyi has been devastating since its appearance on the Caspian Sea, causing unprecedented decreases in mesozooplankton biodiversity and biomass, resulting in a collapse of fisheries on small pelagics. The occurrence of B. ovata in the Caspian Sea is of significant interest for scientists, environmental managers and other stakeholders like fishermen since this new invader had already shown its ability to help in recovery of the fish stocks and ecosystem in whole in the Black Sea. Based on the outcomes of intensive field and laboratory studies in these neighbouring seas, we could suggest that the arrival of B. ovata also will result in the recovery of the Caspian Sea ecosystem.

Recently, the ecology of the Caspian Sea has undergone with increasing development of human activities and industrial wastewater discharges. Heavy metal compounds are undegredable pollutants and are able to accumulate in the environment. They can affect the food chain and biological individuals such as fish species. 40 and 22 samples of Rutilus frisii kutum and Liza saliens were collected in central and eastern parts of southern Caspian Sea in 2008, respectively. All samples were analyzed based on standard methods using Atomic Absorption instrument (Thermo, M5 model). Results of this study showed that the amount of Zn in fish muscle of L. saliens was maximum (415.3±196.3 µg/g. dw). The concentrations of Cu, Ni, Pb, Cd and Hg in fish muscle of L. saliens were 10.85 ±11.02, 0.41 ±0.84, 2.63 ±2.67, 0.63 ±1.07 and 1.30 ±0.16 µg/g. dw, respectively. The concentrations of Cu, Ni, Pb, Cd and Hg in fish muscle of R. frisii kutum were 0.40 ±0.46, 0.0132 ±0.007 and 1.26 ±0.75 µg/g. dw, respectively. 7 heavy metals were below the established limits of different countries. The pearson correlation analysis showed that between Zn and Hg there were a significant negative correlation indicating a decrease of Hg toxcicity with increasing Zn concentration. THQs for individual metals were lower than USEPA guidelines value of 1 in young and adults human. Thus, consumption of 6 kg R. frisii kutum and/or L. saliens per capita cannot be risky for young and adults consumers.

Reproduction period, spawning peak and sexual maturity in anchovy kilka were investigated during the year 2006 for sustainable yield assessment in Iranian waters of the Caspian Sea. The mean fork length, total weight and age were 118±5.9mm, 11±1.7g and 4.6±1.2 year, respectively. Mean (±SD) absolute fecundity was 12625±5533 ovules. More than 50 percent of the fish specimens matured when their length exceeded 92.5mm. The results showed that reproduction of anchovy kilka occurred in autumn, and spawning occurred throughout the year and especially in winter. The length and age ranges were found to be shortened compared to the past years with many older fish and less younger ones (< 2 years) in the catch which sharply decreased recruitment. This phenomenon is thought to be due to overfishing synchronized with invasion of M. leidyi pushing kilka to spawn in winter, which all cause collapse of anchovy kilka stocks in the Caspian Sea. We postulate that anchovy kilka has adopted the strategy of spawning year round to mitigate the negative effects of overfishing and invasion of M. leidyi.

In this study, shelf life of brined vacuum-packed (VP) Golden Mullet (Liza aurata) of Caspian Sea was assessed, considering its protein and lipid deterioration with effect of microbial population during 90 days of storage at 4ºC. Total Volatile Nitrogen (TVN) was measured to determine protein deterioration, Peroxide Value (PV) was analysed to determine lipid deterioration. Total Count (TC), Halophilic Bacterial Count (HBC) and possibility of Clostridium botulinum existence were measured to determine microbial population. TVN increased from 14.5 to 30.80 mg/100g, PV increased from 3.89 to 28.86(meqo2/kg), TC increased from  log 4.40 CFU/gr to log 5.70 CFU/gr and HBC increased from  log 4.75 CFU/gr to log 6.30 CFU/gr. Increasing in some of parameters, was found to be statistically significant in the VP brined golden mullet through out storage (P<0.05). No trace of Clostridium botulinum existence was detected during the period of storage. The results from this study clearly suggested that a combination of brining, vacuum packaging and storage at refrigerated temperature prolongs the shelf life of golden mullet. Based on data the best shelf life was found 30 days for VP brined golden mullet stored at 4ºC.

The effect of different sublethal concentrations of diazinon at 1, 2 and 4 mg/L on some hematological and biochemical parameters of grass carp (Ctenopharyngodon idella) weighing 850±155g was studied after 1, 7, 15, 30 and 45 days post exposure to the toxicant as a bath for 12 hours at 18-22 ºC. In one day exposure fish to the toxicant, the values of neutrophiles exposed to 2 and 4mg/L were significantly higher than control fish, while lymphocyte and monocyte counts in fish exposed to 2 and 1mg/L were significantly lower than control one (P0.05). Seven day after exposing fish to the toxicant, values of WBC in all experimental fish were significantly higher than control fish, while level of neutrophiles in fish exposed to 1mg/L and values of lymphocytes in fish exposed to 2 and 4mg/L were significantly higher and lower than control fish, respectively. Also, values of ALT, AST and ALP in all experimental fish were significantly lower, higher and lower than control fish, respectively (P0.05). Forty five days post-exposing fish to the toxicant, the values of WBC and heterocytes in all experimental fish were significantly higher than control one, while levels of lymphocytes, ALT and ALP were lower than control fish (P