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The study on the ecophysiological impacts of stress in female Persian sturgeon broodfishes revealed that the average cortisol level varried in all broodfish caught at the Sefidrud River (163.38±21.2ng mL^-1), Sefidrud River estuary (260.27±19.7ng mL^-1) and Gorganrud River estuary (179.38±20.8ng mL^-1). The variations in serum glucose levels were 140.65±12.05mg dL^-1, 144.44±5.9mg dL^-1 and 126.24±11mg dL^-1, respectively. The maximum level of cortisol  (781 ng mL^-1) and serum glucose (281 mg dL^-1) were observed during the transport of broodfish from the capture stations to the hatcheries and the minimum level of cortisol (25.2 ng mL^-1) and serum glucose (33 mg dL^-1) were observed during the confinement of broodfishes in the breeding ponds. The rhythmic and significant variations of cortisol level during capture, handling, transport and confinement of female Persian sturgeon broodfish in all three regions can be regarded as a valuable indicator of stress

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Apoptosis is a programmed cell death that has been attributed to the action of stress hormones, such as cortisol. We investigated the in vitro effect of cortisol in goldfish (Carassius auratus) mature (GSI: 2.75-4.65) or immature (GSI: 1.94-2.4) testes. Testes were taken out and transferred into culture medium (M 199), cut into 20 mm thick slices and supplemented with fetal bovine serum (FBS), added different doses of cortisol (0, 50, 100, 200, 400, 750 and 800 ng/ml) and incubated for 24h, 48h or 72h at 18°C. Samples were rinsed and homogenized with phosphate buffered saline (PBS) after incubation period. Duplicates or triplicates processed for caspase-3 activity. The results showed a significant increase in caspase-3 activity in immature testes after 72h treatment with 750ng/ml of cortisol (P<0.05), and also at 400ng/ml (P<0.05). In contrast, no significant differences were observed between non-treated and cortisol-treated samples from mature goldfish testes. In this study we have demonstrated, for the first time that the stress hormone cortisol induces apoptosis in the goldfish testis in a stage-specific manner (immature testis).

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The salinity tolerance and hydromineral regulation capabilities of juvenile great sturgeon, Huso huso, of different age and size groups (1: 35 days, BW: 0.60±0.02g &TL; 4.80±0.13clp; II: 35 days, BW: 2.23±0.20 g & TL: 7.19±0.17cm; III: 35 days, BW: 9.91±0.23g& TL: 11.86±0.24cm; IV: 50 days, BW: 3.97±0.25 g & TL: 9.34±0.18cm; V:50 days, BW:22.27±1.9g & TL: 17.25±0.35cm; VI: 65 days, BW: 6.3±0.67g& TL: 11.37cm ; n=90 for each group) in freshwater (FW:0.5% 0), estuary water (EW:9.5 %0)'and the Caspian Sea water (C_sW:12.5% 0) were investigated. The fishes are directly transferred from FW to EW and C_sW. The possible repercussions of osmoregulatory processes on some indicators of classical were examined at the end of 168 hours fish acclimation. Mortality was observed (higher than 50% after 72 hours) only in 1stgroup in EW and C_sW. Some haematological parameters, namely haematocrit (Hct), red and white blood cells count (RBC, WBC), mean cell volume (MCV), hemoglobin concentration (Hb), mean cell hemoglobin concentration (MCHC), the amount of haemoglobin per erythrocyte (MCH), levels of cortisol, osmolarity and ion concentration (Na⁺, K⁺, .16 S.M. Farabi et ai., Ca⁺² and Mg⁺²) in the plasma were determined. The functional levels of the mechanism of osmotic and ionic homeostasis were similar in different groups (II to VI) but differed in experimental media (p<0.05). Significant differences were observed between the levels of serum Na⁺ concentration in different groups in EW and C_sW media (p<0.05). Serum Na⁺ and Ca⁺² concentrations were higher than those of FW and EW media, but lower than in C_sW media. The Hct, MCV and MCH decreased with increase in fish age, and decreased from FW media to CsW media with increasing salinity; RBC, WBC and MCHC did not change. The trend of increasing levels of cortisol were observed at higher salinity in each group (p<0.05). However, Hct, MCV, MCHC, cortisol, osmolarity and ion concentration values did not return to initial values (P<0.05), showing that osmoregulatory processes caused major physiological changes in this species.

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  Gravid wild kutum broodstock, Rutilus frisii kutum, on their upstream migration to Valiabad River (northern Iran) were kept in captivity to allow them to ovulate (captive ripe). Then the impact of captivity on some reproductive and physiological parameters (i.e., plasma cortisol and glucose levels, fertilization percentage, gonadosomatic index and fecundity) were assessed and results were compared with those obtained from naturally ovulated broodstock (ripe). Plasma cortisol level was not significantly different between gravid and captive ripe broodstock but was significantly higher (P<0.05) than that in ripe group. Glucose level was significantly higher (P<0.05) in captive ripe compared to that in ripe or gravid groups. Mean gonadosomatic index, fecundity, and fertilization rate did not affect as a result of stress by captivity. Inverse relationship between plasma cortisol levels and fertilization rate was observed.

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  The salinity tolerance, hematological and hydromineral regulation capabilities of juvenile Russian sturgeon (Acipenser gueldenstaedtii) were investigated in different ages and sizes in freshwater (FW: <0.5‰), estuary water (EW: 9.5‰) and Caspian Sea water (C_SW: 12.5‰). The fish were directly transferred from FW to EW and C_SW. The possible repercussions of ion-osmoregulatory processes on some classical indicators were examined at the end of 168 hours fish salinity tolerance. The mortality was not more than 35% in EW and C_SW in both groups. The survival percent and salinity tolerance were increased with increment of age and size of fish. The functional mechanism of osmotic and ionic homeostasis were similar in all groups (p>0.05) but differed in experimental media (p<0.05). Signifi cant differences were observed between the levels of plasma ion concentrations in different media (p<0.01). Plasma Na⁺, K⁺ and Ca⁺² concentrations were higher than those of FW media, but lower than in C_SW media (p<0.05). Plasma Mg⁺² concentrations were lower than those of FW and C_SW media, but near to EW media (p<0.05). The hematocrit mean cell volume decreased but mean cell hemoglobin concentration, osmolarity and levels of plasma cortisol were increased from FW media to C_SW media (p<0. 05). The hemoglobin concentration (Hb), the amount of hemoglobin per erythrocyte, red and white blood cells count did not change (p>0.05). However, the results showed that the above parameters in fish fingerlings did not return to initial values in the new environment and then physiological changes happened.

  

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Osmoregulation capabilities of two size groups (1 and 2g) of zander , Sander lucioperca, fingerlings were investigated survival rate, plasma osmolarity, sodium (Na+), chloride (Cl-) ion concentrations and cortisol level within 0, 6, 24, 72 and 240 h after abrupt transfer from freshwater to 7 and 12‰ salinity. Also, some hematological parameters were measured at 240h. The plasma osmolarity and ion concentrations (Na+, Cl-) increased immediately after the transference to 7 and 12‰ salinity, reaching maximum at 72h in 1g and at 24 h in 2g fingerlings, and significantly decreased at 240 h, while the freshwater control group maintained almost constant during 10 days which showed lower than the salinity groups. The pattern of cortisol level changes was similar in two size groups after exposure to different salinities and it reflected stress of handling. There were no significant differences between hematological values of two salinity treatment groups than the freshwater control at 240h. The result showed, not only 2g zander fingerlings acted better than 1g in faced with salinity but also the fingerlings weighing 1g could survived and tolerate Caspian Sea water salinity up to 12‰. It is suggested that the release of zander weighing from 1g would help to restocking management of this species in the southern Caspian Sea.

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The present exposition was designed to evaluate blood serum changes in tiger grouper, Epinephelus fuscoguttatus in response to changes in water temperature and salinity. Uniformly sized fingerlings were randomly distributed into different groups at fifteen fish per tank, in two replicates. Each group represented experimental fishes subjected to water temperatures of 18, 24, 28 and 30°C (control), and salinity of 10, 20 and 30 (control) ppt respectively. Replicate groups of fishes in each tank were exposed to these physiological stressors for 4 and 36 hours. At the end of experiment, blood samples were collected via caudal vein. The collected blood was centrifuged to obtain serum, andanalyzed for cortisol and glucose concentrations, using ELISA method. Results showed that decrease (to 28, 24 and 18°C) in water temperature from the control (30°C) and salinity from 30 ppt to 20 and 10 ppt for 4 and 36 hours influenced changes in the physical appearances (skin coloration) and behaviors (swimming vigor, opercula movement and schooling) of fish, to suggest responses to stress. Further, analyses of serum cortisol revealed consistently higher concentrations at the lower temperatures tested (to 28, 24 and 18°C), than the optimum tolerated by the species. Interestingly, fish maintained at 28°C for 36 hours contained lower serum cortisol concentrations compared to control groups. Meanwhile, the increment of the serum cortisol concentration occurs at decreased water salinity from 30 ppt to 20 and 10 ppt for 4 and 36 hours. It is concluded that: 1) water temperature and salinity are important physiological stressors; 2) sudden alteration of these factors leads to stress, and should therefore be avoided or minimized; 3) results of the present trial suggest that the blood serum factors are reliable parameters for evaluating the level of stress in fish.

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Caspian kutum fish (Rutilus frisii) wild broodstocks were caught by gillnet during their upstream migration and subjected to short-time confinement stress and their physiological responses have been examined. Thirty fish (average weight of 1217.6 g) were divided into three experimental groups CO (control), OV (ovaprim) and CO+OV (cortisol+ovaprim) and placed into rearing tanks (10 fish tank^-1; 2 m³ each) and kept for 10 days. Fish in CO+OV group received a single cortisol injection (20 µg kg^-1 B.W.) before being transferred in tank. After 10 days of confinement, all fish in OV and CO+OV groups  were injected by ovaprim (20 µg kg^-1 B.W.) to induce maturation and ovulation. Plasma cortisol in CO+OV fish have showed a gradual decrease during confinement and reached to the lowest level after maturation (ovulation) while the highest values for glucose has been found in OV group (p<0.05). Testosterone and 17β-estradiol levels declined significantly in all experimental groups following cortisol treatment and maturation, while no significant difference had been found in the content of plasma progesterone among brood-stocks (p<0.05).The concentration of oocyte cortisol in CO+OV was 2-fold higher than that of CO and OV after maturation. These results indicated that cortisol treatment with subsequent ovaprim injection decreased plasma sex steroids and increased oocyte cortisol content in confined broodstocks but had no effect on oocyte histological characteristics.

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The experiment was conducted to determine the effect of salinity and dietary protein levels on  physiological and haematological changes as well as growth of the juveniles of hybrid tilapia (Oreochromis mossambicus×Oreochromis niloticus). Fish were stocked at 20 fish 50L^-1. The initial average weight of the juveniles was 2.1±0.02 g and they were kept in salinities 0, 10, 20 and 35 ppt (S1, S2, S3 and S4, respectively) and fed with 30% (P1) and 40% (P2) dietary protein levels for 45 days. The harvesting weight and SGR were not significantly (p>0.05) different between S2 and S3 treatments for 30% to 40% protein levels varied in connecting S2-S3 with P1diets or in between S2-S3 with P2 diets. The food consumption significantly (p<0.05) increased with decreasing protein levels (40% to 30%) in diets at 10-20 ppt salinities. The survival rates were not significantly (p>0.05) different between 10-20 ppt salinities with P1 and P2 diets. The lowest FCR and highest muscular hydration were achieved at intermediate salinities with low protein diets. No obvious changes occurred in Hct%, Hb, plasma protein, muscles and liver protein levels in all treatments. Furthermore, the plasma cortisol and glucose levels tended to increase at higher salinities but were not significantly (p>0.05) different among all treatments. The physico-chemical parameters of water (i.e. dissolved oxygen: DO, temperature, ammonia etc.) were at a normal range throughout the study. Results showed that environmental salinity (0-35 ppt) had no adverse effects on growth and biochemical changes and also no required high protein levels in diets at any salinity.

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The aim of this research was to evaluate the effects of dietary nucleotides on performance, immune system and salinity resistance of kutum fingerlings during migration to the sea. Five experimental diets were prepared by addition of Hilyses (0.75 and 1.5%) and/or Augic¹⁵ (0.3 and 0.6%) to a control diet. After eight weeks adding nucleotide diets, fish were exposed to saline water for 48h. Supplementation of both nucleotide sources improved fish growth parameters (p<0.05). Fish mortality was also decreased by the additives in both fresh and sea water. Glucose and cortisol levels significantly decreased with the administration of both nucleotide sources (62 to 69 versus 75 mg dL^-1 for glucose and 6 to 8.5 versus 9.8 mg dL^-1 for cortisol (p<0.05). Supplementation of Hilyses and /or Augic¹⁵ increased lysozyme activity in the blood (p<0.05) and maximum activity has observed in fish fed at high doses of Hilyses and Augic¹⁵diets. In conclusion, an improved performance of R. kutum fingerlings fed on or with both nucleotide sources may suggest that kutum fingerlings require a larger dietary nucleotide at early life stage to control stress related parameters such as cortisol and glucose.

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The present study was conducted to determine the appropriate weight to release the hatchery produced fingerling of stellate sturgeon, Acipenser stellatus, into its natural habitat. For this purpose, prolactin and cortisol hormones, plasma electrolytes and osmolality as well as histological changes in the gill and kidney of stellate sturgeon transferred from fresh to brackish water at different weight (0.5, 1, 2, and 3 g) were assessed during a one-week time course. A total of 2400 fingerlings with different weights (0.5, 1, 2, and 3 g) were equally assigned into 24 aquariums, each one containing 200 L of freshwater or brackish water. After 24 hours, prolactin showed the highest concentration in 0.5 and 3 g fish groups kept in both experimental waters. Cortisol exhibited a time-dependent increase in the 0.5 g group in both experimental waters as well as the 2 g larvae kept in the brackish water. Generally, lower levels of Mg²⁺, Ca⁺²; K⁺, Na⁺, and Cl^- were measured in the fish kept in freshwater aquariums. The lowest levels of osmolarity were found in the 0.5 g fingerling, especially those kept in the freshwater aquariums, whereas the highest levels were observed in 3 g groups in both experimental waters. Histological assessments illustrated that the volume of chloride cells in freshwater increased with increasing fish weight, whereas the cell count decreased. The same held true for glomerular capillary network size. Taken together, the evidence from this study suggests that stellate sturgeon fingerling less than 2 g are almost incapable to be transferred to brackish and saline environment, due to lack of kidney and gill development.