Production of all-female rainbow trout (Oncorhynchus mykiss) using sex-reversed males and investigation of their growth parameters in the first year of culture

Possibility of producing all-female rainbow trout (Oncorhynchus mykiss) using neomale stock were investigated in Kelardasht hatchery. To do this, we compared the fertilization, hatching rate and growth parameters of progeny in the first year of culture. Histological studies of gonads showed that progenies produced by mating sex-reversed males and normal females were totally female. Eyed-stage egg, hatching and early survival rate in all of female population were 90:69 %, 97.36 %, 91.49 % and in mix sex population were 7024 %, 98.22 %, 90.73 %, respectively, showing no significant differences (P>0.05). Lack of maturation in the first year cultured fish led to the identical growth parameters in mix sex and all-female groups (P>0.05). Results showed that use of sex-reversed males can be one of the best and successful methods of producing all-female populations

Blood serum osmotic and ionic regulation of wild adults and reared juvenile Persian sturgeon, Acipenser persicus

The osmoregulatory system was studied in wild adult and reared juvenile Persian sturgeon, Acipenser persicus. The mean osmolarity in blood serum of specimens from the Caspian Sea, estuary, the Kouraneski pools and the rearing tanks were 305.3±14.3, 308.7±25.8, 265.0±19.1 and 259.3±8.8 mosmol/L, respectively; the mean concentrations of Na+ were 151.2±6.3, 152.2±8.4, 142.5±5.9 and 131.4±4.1 meq/L whereas mean concentrations of K+ were 2.7±0.9, 3.6±0.9, 3.1±0.5 and 2.6±0.5meq/L, respectively. The concentrations for Mg++ ion in fish of the same four origins were 1.5±0.2; 1.5±0.3, 0.8±0.2 and 0.7±0.2 meq/L, and those of Ca++ were 2.31±0.51, 2.61±0.51, 1.85±0.58 and 1.46±0.43, respectively. The Pearson's correlation coefficient and regression equation indicated that Mg++(r =0.38) and Na+ (r=0.41) were effective ions for determination of blood serum osmotic pressure in A. persicus in brackish water and freshwater. This study also showed that blood serum osmotic pressure was independent of sex

Comparing sex hormones levels in Acipenser persicus at the onset of autumnal migration

Levels of two main steroid hormones in gonads, 17-B Stradiol (E2) and testosterone (T) were compared in males and females of Persian sturgeon at the start of autumnal migration to spawning rivers. Hormone levels were also studied for likely relationship with different stages of sexual maturity. The results showed that levels of T and E2 in females at the stage four of sexual maturity is significantly higher than the individuals with immature gonads (ovary in stages 2 and 3). We measured 11.81±2.86Omg/ml and 7±1.15mg/ml of T and E2 in mature females compared to 0.2±0.09mg/ml and 0.736±0.161mg/ml of T and E2 in immature females. Levels of the two hormones in males at different stages of sexual maturity showed that only testosterone was significantly different in mature and immature sturgeons (0.50±0.144 mg/ml and al 4.3 I 25±3.121mg/ml in mature and immature males, respectively) (P=0.04). In males and females with higher sexual maturity, differences between the two hormones were significant (T and E2 levels in females and males were 11.81±2.860mg/ml, 7±1.15mg/ml and 0.50±0.144mg/ml, 0.7023±0/212ng/ml, respectively). However, in immature fish of both sexes, only males showed significantly higher T levels (14.312513.121mg/ml in comparison with 0.2±0.09mg/ml). Disregarding the sexual maturity stages, we found significantly different levels of E2 in both sexes (4.779±1.827mg/ml in females and 0.709±0.121mg/ml in males) (P=0.00). Statistical analyses indicated no correlation between fish age and levels of steroid hormones of the fish (at 90% confidence level)

Determination of sex and sexual maturation stages in cultured Acipenser nudiventris using biopsy method

Sturgeon fish take long time to mature sexually and determination of sex and sexual maturity stages is important in artificial rearing of the fish. Sex determination by macroscopic method has thus far been impossible for the fish at juvenile stages. Gonad biopsy and its histological examination is one way for detecting male and female sturgeon fishes. To do so, we collected gonad samples from 13 five year old and 17 six year old specimens of the cultured Acipenser nudiventris. Samples were studied by light microscope after fixing and histological practices. Of the 13 five years old specimens, only 3 (23.1%) were male and 10 (76.9 %) were females. From 17 six years old fish, 10 (58.8%) were males and 7 (41.2%) were females. Histological studies showed that all male fish were at stage IV, but 5.8 % of all females were at stage I, 41.2 % were at stage II and 53 % were at stage II-III of sexual maturation. We also showed that in the studies sample, males reached maturity sooner than females

Biotechnic of brood stocking, artificial propagation and some physiological indices in farmed Acipenser nudiventris

This study was conducted on farmed Acipenser nudiventris at the International Sturgeon Research Institute from the winter of 2007 till summer 2010. A total of 11 farmed A. nudiventris specimens (7 male and 4 female) were stocked in groups of 4 fish in eight fiberglass tanks (4 tons capacity) on the basis of their sex. Males were fed with a diet with no soybean but containing vitamins. Females were fed with a diet containing soybean and vitamins with 38-40% protein, 13-15% fat, 19.5-20Mj/kg energy, respectively. GnRH was used for artificial propagation of Acipenser nudiventris brood stocks twice for females (dose 10µg/kg with 80:20 ration) and during one occasion for males with a dose of 20 µg/kg. The results of the study indicated that food composition (soybean and vitamins C and E) played a significant and positive role in the reproduction system for females. No significant effect of treatment was observed in Testosterone levels between mature (Mean ±SD: 60.6±8.07ng/ml) and immature (24.42±4.87ng/ml) males, Likewise, no significant differences were found in17α-Hydroxy Progestrone for female (Mean ±SD: 0.106±0.019ng/ml) and for immature fishes (0.031±0.006ng/ml) significant differences was detected in the concentration of Albomine (1.54±0.05mg/dl for females and 1.35±0.07mg/dl for immature females), but there were no significant differences in other biochemical parameters including Glocose, Cortisol, Chlosterole and Triglisride in males and females. There were no significant differences in total weight and length, WBC, RBC, Hb, Hct, MCH, MCHC and MCV parameters in males and females. This study is a step forward towards the development of artificial breeding and rearing sturgeon fish in the country

Effects of different dietary levels of AFB1 on survival rate and growth factors of Beluga (Huso huso)

In the present study, the impacts of various concentrations of Aflatoxin B1 (AFB1) on Beluga, Huso huso, under controlled conditions were investigated. Belugas (120±10g) were fed on diets containing 0, 25, 50, 75, and 100 ppb AFB1/kg of diet for 3 months. Results showed various levels of AFB1 do not significantly affect the specific growth ratio (SGR) (P<0.05) of fish in different treatments. However, weight gain and food conversion ratio (FCR) were varied significantly (P<0.05 between control and treatments with diets contaminated with 75 and 100 ppb AFB1/kg after 90 days). The increase AFB1 level of did not affect on the percent of survival rate (SR) and no mortality was observed in treatments (SR=100%) suggesting that various AFB1 levels under experimental conditions of the present study affect some growth factors, such as, weight gain and FCR but have no significant impact on SR and SGR. Histopathological studies showed that different level of AFB1 can cause broad range of change in liver tissue, including progressive fat deposition, hepatocyte degeneration and necrosis, particularly at concentration of 75 and 100 ppb AFB1/kg of diets after 60 days

Determination of lethal range and median lethal concentration (LC50 96h) values of diazinon on Caspian Sea common bream (Abramis brama)

Pesticides are environmental contaminants which normally enter to aquatic ecosystems after being used in aquaculture. In this research, acute toxicity of diazinon was studied on Caspian Sea common bream (Abramis brama). This pesticide may enter in aquatic food chain and cause serious problems for aquatic organisms as well as human. The acute toxicity test was performed during 96h in static renewal system based on the standard method proposed by OECD. A range finding test was carried out in aquariums containing 10L of test solution to determine the lethal range of diazinon on fish. The acute toxicity test was then preformed in 5 treatments and 3 triplicates for each treatment. Obtained data were analyzed using probit analysis with %5 confidence limit. According to the results, LC_50 24h, LC_50 48h, LC_50 72h and LC_50 96h of diazinon on Caspian Sea common bream was 10.974, 10.391, 9.134 and 7.316 respectively. The maximum acceptable toxicant concentration (MATC) of diazinon on Caspian Sea common bream was 0.073 mg/l and the lowest observed effect concentration which is equal to LC_50 96h was 2.63 mg/l. According to the results and comparing with other studies, it can be discussed that Caspian Sea common bream is more resistant against diazinon rather than other fish species. In addition, lethal toxicity of diazinon takes place in a moderate range of toxicant concentrations

Study of kidney and gill function in Salmo trutta caspius fingerlings after move to the Caspian Sea

Caspian trout (Salmo trutta caspius) is an anadromous and valuable fish species in the Caspian Sea. Electrolytes concentration (Mg2+ and Ca2+) and kidney and gill development trend were studied in different weight groups. Specimens in 4 weight groups 5, 10, 15 and 20g. Each trial was done in 3 replicates. The observation of kidney glomeruli in histological sections showed that the diameter of glomeruli in all weight groups in Caspian water decreased after 72h adaptation period (P0.05), although in other groups (10, 15 and 20g) a significant increase in chloride cell's number and size was detected. The number of chloride cells on gill's secondary lamellas varied between 3 to 7 (in two gills lamellas)

Determination of optional weight and length of Persian sturgeon's fingerling Acipenser persicus on the salinity index in the southern part of Caspian Sea

The Persian Sturgeon, Acipenser persicus is the most important sturgeon species in the southern part of the Caspian Sea and it provides 51% of Iran's caviar production. We were used five different age groups of the larvae (7, 17, 22, 28 and 33 days after yolk absorption) in 3 replicates. The larvae were all transferred at the same time to 27 liter aquarium holding 15 liter of water at different salinities (0.5, 7 and 9 ppt) and were provided with continuous aeration. Analysis of data showed that during early stages of life, age is an important factor for development of osmoregulatory organs. However, in later stages, weight and length play a vital role in this regard. The present study reveals that during post hatch and active feeding, in favorable environmental and rearing condition A. persicus fingerlings could be released into rivers and estuaries in Guilan province at an age of 33-35 days after yolk sac absorption and when they attain weight of 1.8-2.4g and length of 6.2-7.5cm

The study of skin lesions in beluga (Huso huso) fed with different dietary levels of Aflatoxin B1

In this study, 180 Beluga (Huso huso) weighing 120110g each with a stocking density of 12 fish per tank were adapted with synthetic diet and then fed with different levels of AFBI (0, 25, 50,75 & 100pplpikg of diets) under controlled conditions (T=1 8±2°C, DO=7.3ppm). The fish were fed 3% of their body weight four times a day for three months. Prevalence of skin lesions evaluated through clinical observations monthly. With regard to toxin concentration and time of exposure to AFBi in experimental fish, different degree of skin lesions (simple hemorrhage to progressive wounds) were observed in different parts of body especially in vent, caudal peduncle, fins, and head. "Yellow sores" on head and trunk regions were considerable and led to deterioration of appearance. Prevalence of skin lesion in different treatments was 8•m53.3%. After feeding with toxic diets was stopped, 16.w24% healing was obsenTed in the fish