Effects of different carbon sources on water quality, growth performance and survival of western white shrimp (Litopenaeus vannamei Boone, 1931) in zero-water exchange system

Effect of different dietary carbon sources on water quality, growth performance and survival of western white shrimp Litopenaeus vannamei post larvae was investigated in zero-water exchange system. Shrimp postlarvae with mean weight of 98.47±8.60 mg and mean length of 22.39± 1.70 mm were fed for 32 days in fiberglass containers with 130 liters volume of water and density of 1 individual per liter in five treatments including one control with water exchange and four biofloc treatments with adding different carbon sources including molasses, starch, wheat flour and mixture of them at equal weight ratios with 15% to 9% of body weight. In the values of water quality parameters including temperature, salinity, dissolved oxygen and pH, no significant differences were observed among the biofloc treatments (P>0.05). Maximum pH (8.27 ± 0.09) and maximum dissolved oxygen (6.37 ± 0.56 mg/lit) was in water exchange treatment. Maximum and minimum level of ammonia was 0.43± 0.34 and 0.09± 0.07 mg/lit in water exchange treatment without floc and biofloc treatment with adding starch of carbon sources, respectively and showed significant difference between treatments (P <0.05). The highest increase in body weight (1640.43± 231.28 mg), growth rate (51.26± 7.23 mg per day), specific growth rate (8.97± 0.42 %/day) and biomass (190.29± 26.83mg) was observed in biofloc treatment with adding molasses and the highest survival rate (90± 0.77%) was obtained in biofloc treatment with adding mixture of carbon sources. The highest feed conversion ratio (1.52±0.23) and the lowest feed efficiency (66.81±7.95) were obtained in water exchange treatment without floc, showing significant difference compared to the other treatments (P <0.05). The results showed that using biofloc technology with zero- water exchange system and adding carbonaceous organic matter could help to recycle waste and improve the water quality. Moreover, the presence of biofloc improved growth performance, feed utilization and production of western white shrimp in zero water exchange rearing system

Study on nursery growth performance of Pacific white shrimp (Litopenaeus vannamei Boone, 1931) under different feeding levels in zero water exchange system

Effect of different feeding levels on water quality, growth performance, survival rate and body composition of Pacific white shrimp Litopenaeus vannamei post larvae were studied in zero water exchange system. Shrimp post larvae with mean weight of 74.46± 6.17 mg were fed for 32 days in 300L fiberglass tanks containing 130L water at density of 1 post larvae L^-1. There were five treatments including control and four biofloc treatments with different feeding levels of 15%, 15%, 12%, 9%, 0% of body weight per day, respectively. The results showed that there were no significant differences in water parameters such as dissolved oxygen and pH between different treatments (p>0.05). There were significant differences in water ammonia level between different treatments (p<0.05). The maximum (0.39 mg/L) and minimum (0.12 mg/L) levels of ammonia were observed in control and biofloc treatment with minimum feeding level (9%BW/day), respectively. The highest body weight gain (1.55g), growth rate (48.50 mg per day), specific growth rate (9.64%/day), biomass gain (182.1g) and body length increase (33.62mm) were observed in biofloc treatment with maximum feeding level. The highest feed conversion ratio and the lowest feed efficiency were obtained in control (p<0.05). The proximate body composition analysis revealed an increase in lipid, protein and ash in biofloc treatments. Results showed that using biofloc technology can decrease water exchange amount and improve feed utilization in nursery culture of Pacific white shrimp. Moreover, presence of biofloc improved the water quality which led to the enhancement in growth performance in nursery stage of shrimp

Toxicity comparison of silver nanoparticles synthesized by physical and chemical methods to tadpole (Rana ridibunda)

One of the possible threats in increasing use of nanomaterials is the emergence of toxicity in humans and other animals which is discussed in nanotoxicology. In addition to toxic effects of nanomaterials themselves, different chemical precursors which are usually used in bottom-up approaches for production of nanomaterials may have secondary toxic effects in living organisms. In contrast, less use of chemicals in top-down approaches may reduce these secondary effects. To test this hypothesis, toxic effects of two types of silver nanoparticles (AgNPs) produced by physical (top-down) and chemical (bottom-up) methods were investigated and compared on the tadpole, Rana ridibunda survival. The estimated 48 h LC50 values of AgNPs produced by chemical and physical methods for tadpoles were 0.055 ± 0.004 and 0.296 ± 0.085 mg.L-1, respectively. No observed effect concentration, lowest observed effect concentration, maximum acceptable toxicant concentration and median lethal concentration of AgNPs produced by chemical method were respectively 3.42, 4.50, 4.84 and 5.38 times less than those produced by physical method. Therefore, approving the mentioned hypothesis, it was revealed that AgNPs produced by chemical method are more toxic than those generated by physical method. However, it seems totally that AgNPs regardless of the method used for their production, have toxic effects on aquatic organisms and so, inhibiting their accidental or intentional entrance into the aquatic ecosystems should be more considered

Equalization of sperm concentration of Caspian brown trout Salmo trutta caspius male breeders in mixed milt fertilization and its effect on genetic diversity of F1 progeny

Conservation of genetic diversity of juveniles used for restocking of natural populations requires serious attention in artificial breeding protocol of the Caspian brown trout Salmo trutta caspius. Unbalanced contribution of male and female breeders to progeny in present artificial breeding has resulted in the reduction of effective population size in breeders. Equalization of milt volume did not also result in balanced contribution of breeders. With regard to the possible effect of sperm concentration on contribution of breeders to production of progeny, effective population size in breeders and genetic diversity of progeny were determined in mixed milt fertilization of 6 male and 2 female breeders with equal sperm concentration and ova number. Parentage assignment was performed using exclusion method in FAP program by analyzing 9 microsatellite loci and choosing the 3 most polymorphic ones, Str 58, Str 73 and Str 591, in breeders. More than 91% of progeny were assigned to their parents. Effective population size was calculated as 5.24 (0.65) and the number of alleles and expected heterozygosity decreased in progeny (6.67 and 0.726 ± 0.011) compared to parents (7.33 and 0.808) significantly (P>0.05). In conclusion, equalization of sperm concentration of male breeders did not result in the balanced contribution of male breeders to ova fertilization and production of progeny in mixed milt fertilization of Caspian brown trout and genetic diversity of progeny remained significantly decreased

Feeding habits of yellowfin seabream (Acanthopagrus latus) in the northern region of the Persian Gulf

Feeding habits of yellowfin seabream (Acanthopagrus latus) was investigated in coastal waters of the Northern Persian Gulf. This investigation was conducted by monthly sampling of thirty fish from September 2011 through August 2012. Fish size ranged from 17.98 ± 2.07 to 32.31 ± 6.52 cm in total length and from 134.01 ± 45.62 to 720.46 ± 292.58 g in weight. The highest value of gastro-somatic index was obtained in September (5.22 ± 0.04) and the lowest in December (1.61 ± 0.03) with annual average of 2.50 ± 0.60. The result of gastro-somatic index revealed that the highest feeding activity of A. latus was during autumn. The highest level of vacuity index was observed in summer (34.95 ± 4.71) and the lowest in autumn (25.88 ± 2.71) indicating that the highest number of empty stomachs was in summer. Annual average of vacuity index was 30.14 ± 5.72 exhibiting that A. latus was comparatively gluttonous in the Northern Persian Gulf. Bivalves and shrimps were the major food items found in the stomach of A. latus showing food preference indices of 45.86% and 30.67%, respectively. Other food items included crabs (12.66%), aquatic plants (4.05%), animal derivatives (4.52%) and gastropods (2.23%). According to the results, animal derivatives, aquatic plants and gastropods were eaten accidentally and were not the food items of A. latus in coastal waters of Hormozgan. The average relative length of gut was 1.41 ± 0.15 showing that A. latus was omnivorous in this region

Parentage assignment of progeny in mixed milt fertilization of Caspian brown trout Salmo trutta caspius using microsatellite DNA markers: Implications for conservation

Parentage of a stock of mixed milt produced progeny in current artificial breeding protocol of endangered Caspian brown trout, Salmo trutta caspius, was determined using three microsatellite loci chosen after a primary analysis of genetic diversity at nine microsatellite loci in the eight used breeder individuals. Overall, 98.8% of progeny were assigned to their parents using Family Assignment Program (FAP). Selection of hyper-variable microsatellites in Caspian brown trout to identify unique alleles was effective for unambiguous parentage determination and estimation of genetic diversity in this study. Effective population size of breeder individuals (Ne) was lower than the number of breeder individuals used (Nb) indicating unbalanced contribution of breeder individuals to progeny. Indeed, one of the four male breeder individuals produced about 70 % and the other three produced only from 4.86 % to 18.83 % of progeny. The average observed and expected heterozygosity of progeny (0.723 ± 0.011 and 0.684 ± 0.009, respectively) was significantly lower than that of their parents (0.833 and 0.800, respectively). Our data indicate that the current breeding protocol of Caspian brown trout may not provide equal opportunity for all the breeder individuals to contribute equally to progeny. Therefore, appropriate fertilization designs in the hatchery should be established in order to equalize the genetic contribution of different breeder individuals.Key words: Parentage assignment, effective population size, genetic diversity, Salmo trutta caspius

Application of AFLP molecular marker for genetic analysis of black pomfret Parastromateus niger from the Persian Gulf

Black pomfret Parastromateus niger is a commercially important fishery resource in the Persian Gulf but harvesting its stocks lacks genetic identification of populations. AFLP technique was applied to analyze genetic diversity and population structure of 32 fish from coastal waters of Bandar Abbas, Bushehr and Abadan with 7 EcoRI/MseI primer pair combinations. In total, 381 bands were produced of which, 46 were polymorphic (12.07%). Percentage of polymorphic bands was higher in Bushehr samples (91.30%) than in Abadan (84.78%) and Bandar Abbas (73.91%) samples. The highest level of heterozygosity based on Nei’s coefficient and Shannon’s index was observed in Bushehr fish (0.38±0.16 and 0.54±0.21). Observed and effective alleles ranged from 1.73±0.44 and 1.53±0.40 in Bandar Abbas samples to 1.91±0.28 and 1.70±0.34 in Bushehr samples. The average Fst was 0.19 indicating high genetic differentiation among the three locations. Gene flow with mean of 1.93 was the lowest level between Bandar Abbas and Abadan (1.24). Nei's genetic identity revealed the least genetic similarity between the samples of Bandar Abbas and Abadan (0.77). AMOVA analysis demonstrated 81% of the genetic variation within populations and 19% among populations. The UPGMA dendrogram clustered all 32 individuals into 3 groups. In some cases individuals from the same region were grouped together but in most cases, gene exchange was observed to be common among the groups. Analyses provided evidence for genetic differentiation among the three locations, indicating separate populations of black pomfret in the northern Persian Gulf

Effect of different feeding levels on water quality, growth performance and survival of western white shrimp (Litopenaeus vannamei Boone, 1931) post larvae with application of biofloc technology

In this study, effect of different feeding levels on water quality, growth performance and survival of western white shrimp Litopenaeus vannamei post larvae were studied in biofloc rearing system. Shrimp postlarvae of PL10 with mean weight of 3±0.7 mg and mean length of 4.4± 0.93 mm were fed for three weeks in fiberglass containers with 200 liters volume of water and density of 10 post larvae per liter in four tretments including one control with water exchange and three biofloc treatments at different feeding levels of 25, 20 and 15% of body weight. According to the results, in the values of water quality parameters including salinity, dissolved oxygen, pH, nitrite and nitrate, no significant differences were observed among the groups (p>0.05). The highest increase in body weight (58.42 mg), growth rate (2.78 mg per day), specific growth rate (15.09 %/day), biomass (84020 mg) and survival rate (71.9%) were obtained in biofloc treatment at 25% feeding level. The highest feed conversion ratio (2.05) and the lowest feed efficiency (48.62%) were obtained in water exchange treatment without floc, showing significant difference compared to the other treatments (P< 0.05). The results from this study reveals that by using biofloc rearing technology can decrease the amount of water exchange and feed utilization compared to body weight in culture of western white shrimp post larvae. Moreover, the presence of biofloc improves growth performance and production of L. vannamei post larvae in biofloc rearing system