پژوهش های ماهی شناسی کاربردی
سال:1399 | دوره: | شماره: |تعداد مقالات:10

This study was conducted to determine the effects of some environmental parameters (sea surface temperature SST, sea level SL and Volga river water volume VRWV) on biomass of golden grey mullet Chelon aurata in Iranian coastlines of the Caspian Sea. In the study, the catch and population parameters of golden grey mullet during the years 1991-2017 used as input data. In these years, the catch of golden grey mullet ranged from 1425 to 6600 mt. The total biomass increased from 10870 mt in 1991-92 to 20950 mt in 2000-01 and then declined to less than 8800 mt in 2017-18. Also, the biomass of 2 years (as recruitment R) increased from 1757 mt 1991-92 to 2617 mt in 2001-02, then declined to 387 mt in 2016-17. There is a significant negative relationship between R-SST (p<0. 017), and a positive relationship between R-VRWN (p<0. 024) and R-SL (p<0. 002). By using stepwise regression, among three environmental parameters, only SL had significant effects on R biomass (R2 = 0. 339). It seems that the SL has the main role in the biomass of golden grey mullet in the Caspian Sea. Therefore, an ecosystem-based approach to Management is required to sustainably exploit of golden grey mullet stocks in the Caspian Sea.

The present study aimed to describe the otolitxsh morphology of the Caspian kutum (R. kutum) in the southern coasts of the Caspian Sea. The current knowledge on the stock structure is scarce for the management and protection purposes of this valuable species. This study was carried out using sagitta otolith as an effective tool for identification of the Caspian kutum population structure. A total of 153 individuals fish were collected from ten beach seine of bony fish cooperatives in the southern coasts of the Caspian Sea (Astara, Bandar-e Anzali, Rudsar, Tonekabon, Nowshahr, Babolsar, Sari, Miankaleh (Golestan Province), Khajeh Nafas, and Gomishan) from 2016 to 2017. Otolith shape indices were analyzed using univariate and multivariate statistics. Otolith shape analyses showed some regional differences. The rate of reclassification of sampled fish were around 40-60% at the sampling stations which indicating no single population. However, using differential analysis and MANOVA/CVA showed that there were four distinct spatial groups including the first group from Gomishan, the second group from Khajeh Nafas, Miankaleh, Sari, Babolsar, the third group from Nowshahr, Tonekabon, Rudsar and the fourth group from Bandar-e Anzali and Astara. Consequently, data showed the complex spatial dynamics of the Caspian kutum.

To study the effect of Shahid Rajai Dam construction on population dynamics of P. cyrius in downstream of the dam, monthly sampling was carried out using electrofishing from April 2012 to March 2013. A total of 564, 219, and 263 specimens were examined from the first, second, and third station, respectively. The sex ratio of male to female was 1: 1. 42, 1: 1. 2, and 1: 0. 91 in the first, second, and third stations, respectively. Only the first station showed a significant difference with the standard ratio of 1: 1. At the first station, four groups of age composition (0+ to 3+ years) were found, while at the other stations, only three age groups (0+ to 2+ years) were found. A positive allometric growth pattern was found at all stations for both sexes. The relationship between length and weight showed a high correlation (more than 0. 97). Bertalanffy growth equation was calculated for males at the three stations were 134. 73(1 )  1. 067(  0. 689)   t t L e, 144. 39(1 )  0. 803(  0. 832)   t t L e and 187. 07(1 )  0. 483(  0. 896)   t t L e for females, it was 130. 54(1 )  0. 82(  0. 73)   t t L e, 145. 07(1 )  0. 59(  0. 931)   t t L e and 157. 6(1 )  0. 42(  1. 46)   t t L e. The absolute fecundity at the first, second, and third stations was 570. 87, 330, and 303. 5, respectively. The above-mentioned parameters show a significant difference in water temperature among the stations (more than 2º C), which increase the abundance, longevity, and fecundity of P. cyrius. Therefore, it could provide a suitable habitat for P. cyrius.

Despite increasing usage of metal nanoparticles and their applications in various industries, few in vivo studies have examined the side effects of these materials on aquatic animals. Therefore, the present study was carried out to investigate the effect of iron and zinc oxide nanoparticles on histopathological changes in the brain and intestinal of common carp (C. carpio). Four hundred and twenty of common carp (average initial weight; 45± 3. 2 g) were provided and then after disinfection, fish were adapted to laboratory conditions for a week. Samples were randomly divided into seven groups. The first group was the control group and the other groups received 10, 50, and 100 μ g nanoparticle/g dry feed for 60 days. Histopathological studies of intestine showed that dietary iron and zinc oxide nanoparticles caused an increase in muscle layers depending on the exposure time and concentration. Also, iron and zinc oxide nanoparticles caused an increase in neuronal size without any histological changes. It can be concluded that dietary zinc and iron nanoparticles (even in small amounts) affect the histology of different tissues of common carp.

In this study body composition and digestive enzymes activity were assessed in rainbow trout (O. mykiss) fry (weight 2. 51 ± 0. 55 g) fed with bacterial single-cell (BSC) as a dietary protein source replaced with fish meal in a completely randomized design with three replications for each treatment for 6 weeks. Experimental diets were prepared in 5 treatments as isonitrogenous with different levels of fish meal and BSC (100% fish meal (A), 75% fish meal and 25% BSC (B), 50% fish meal and 50% BSC (C), 25% fish meal and 75% BSC (D), and 100% BSC (E)). The body composition findings showed that the highest lipid and protein and the lowest moisture and ash was revealed in fish fed with diet C while the lowest lipid and protein and the highest moisture and ash was observed in fish fed with diet E. Enzymatic assessment from pyloric caeca and intestine showed that trypsin and α-amylase were increased significantly in fish fed with diet C. Moreover, alkaline phosphatase activity in fish fed with diet D was higher than those in diet E. Based on the results of this study, it is recommended that BSC could be properly replaced up to 50 % with fish meal in the diet of rainbow trout fry.

To survey the effects of dietary thyme extract on common carp (C. carpio), 180 fish (average weight; 10. 84± 0. 063) were divided into four groups with triplicates (each replicate with 15 fish) and fed with different levels of dietary thyme extract including 0, 0. 5, 1, and 2 % for 70 days. At the end of the rearing period, 30 fish from each group were exposed to 13 ppt salinity for 12 h and were studied for hematological parameters. Blood samples were withdrawn from caudal peduncles before and after 6, 24, and 72 h salinity stress. In the present study, thyme extract supplementation in diet had no effect on growth performance. Hematology investigation after salinity stress revealed an increment in hematocrit level in the 0. 5 % treatment compared to the control group. Also, the hematocrit level was significantly different in 1% and 2% treatments compared with the control after 72 h salinity stress. Hemoglobin levels were significantly increased in treated groups after 6 h salinity stress. White blood cells (WBC) number, red blood cell (RBC) number, and hematological parameters (MCV, MCH, MCHC value) didn’ t show significant differences among all studied treatments. Consequently, 0. 5, 1, and 2 % of dietary thyme extract had no effect on growth performances and hematological parameters in common carp during salinity stress conditions.

This study carried out to investigate the live food selectivity of Persian sturgeon (A. persicus) fry in six treatments in four earthen ponds during spring 2013 for 40 days. For this purpose, sampling was performed from zooplankton and benthos of earthen ponds and stomach content of 240 fry. In order to determine the electivity index for each prey item, the abundance of prey in the stomach and earthen ponds was investigated. The range of electivity was from-1 to 1, where 1 indicates positive selection for prey items and-1 indicates avoidance of prey items and zero shows random selection. The frequency of rotifer and daphnia were 172. 6 and 123. 8, respectively, and they were dominant among the six aquatic animals at treatment 6. The chironomid larvae (Chironomus sp. ) had the highest frequency of 40. 25 in the third sampling. Although the content of the stomach was daphnia, diaptomus, chironomid larvae (Chironomus sp. ), daphnia, and chironomid larvae were the dominant organisms. The highest positive electivity of daphnia (0. 83) was observed in treatment 3, while, the highest frequency of chironomid (0. 59) was detected in treatment 6. After 30 days, a strong positive selection for chironomid and weak positive selection was observed for daphnia.

The present study examined the effects of various concentrations (0. 1, 0. 3, 0. 5, 0. 7, 0. 9, and 1. 1 ml L-1) of 2-phenoxyethanol as an anesthetic agent on stress responses, hematological parameters, and hepatic enzymes in Siberian sturgeon (A. baerii). The results showed that exposing Siberian sturgeon to low concentrations of 2-phenoxyethanol prolonged deep anesthesia compared to higher concentrations, although the recovery time was significantly decreased. Furthermore, cortisol levels significantly increased at low (0. 1-0. 5 ml L-1) and decreased at high (0. 9 and 1. 1 mg L-1) concentrations compared to the control group. Different concentrations of 2-phenoxyethanol had no effect on the levels of WBC, while significant increments were observed in the levels of RBC, hemoglobin, and hematocrit at 0. 1 and 0. 3 ml L-1 concentrations. No changes were observed in the blood minerals as well as MCV, MCH, and MCHC. Higher ALP and AST were detected in the low concentrations (0. 1 and 0. 3 ml L-1) compared to those in the control and high concentrations groups. In conclusion, these findings showed that 2-phenoxyethanol at 0. 9 and 1. 1 ml L-1 concentrations could be more suitable to use as an anesthetic agent in Siberian sturgeon, characterized by the least impacts on the physiological conditions.

In the present study, the effects of intraperitoneal injection of Carthamus tinctorius extract on the non-specific immune system and some serological parameters of rainbow trout (O. mykiss) were investigated. Fish (average weight of 100± 10 g) were intraperitoneally injected by different levels of safflower extract. In this regard, fish were divided into five different groups including two control groups: one negative control group (no injection) and the other positive control group (injection of 0. 2 ml physiologic solution). The other three groups received 50, 100, and 200 mg/kg of C. tinctorius extract, respectively. Blood samples were taken on the third, seventh, and tenth days after injection and then total protein, total immunoglobulin, lysozyme activity, complement, and glucose levels were determined. The results showed that safflower extract injection led to a significant decrease in the number of white blood cells on the third, seventh, and tenth days. Moreover, glucose, lysozyme activity, total immunoglobulin, and total protein levels significantly decreased. There was no significant change in complement activity among all groups. According to the results, the utilization of safflower extract can decrease the non-specific immune system activities in rainbow trout.

Zrebar Lake is one of the most important natural freshwater lakes in Kurdistan Province in the west of Iran. Since December 2019, there have been reports on an unusual fish species sighting in the Zrebar Lake. So, efforts were made to set traps, capture, and identify the species as Northern pike (E. Lucius). The preliminary results showed that the captured fish (E. lucius) was recorded with an average body weight of 630. 3± 182. 1 g, a total length of 418. 4± 41. 3 mm, and at the age of 2. 7± 0. 5 years. The mean number of eggs per gram in females was 171. 9± 26. 3 and the stage of female sexual maturation was determined to be 5. 13± 0. 35 years (the lowest stage at age of 5 and the most stage at age of 6 years) and the stage of male sexual maturation was 2. 5± 0. 57 years (the lowest stage at age of 2 and the most stage at age of 3 years). Based on the RLG index (0. 98± 0. 12), the Northern pike was categorized as a carnivorous species characterized by their type of prey: Carassius auratus (Carucian Carp), Squalius cephalus (Common Chub), Alburnus sp. (Bleaks), and frogs (adult) in the gastrointestinal tract. Based on the feeding habit study, the Northern pike can be classified as an invasive fish species by their directly or indirectly impacts on the population of a variety of aquatic species in particular fish and amphibians. The first observation of the reproductive organs of both sexes showed that they are considered mature sexually. Suggesting that the accidental introduction of Northern pike can cause serious threats to the population of native fish species and this freshwater ecosystem.