مجله علوم و فنون دریایی
سال یازدهم شماره 2 (تابستان 1391)

Effect of salinity levels on density and population growth of parthenogenetic Artemia were studied. Cysts were hatched and 200 nauplii were transferred into cylindro-conical containers (1.5 liter) containing one-liter water at different salinities (50, 100, 150, 200 and 250 ppt) and cultured until maturity. After maturity, 3 female parthenogenetic Artemia were selected randomly from each of the five levels of salinity and cultured in 4 replicates for 12 weeks. The growing Artemia were categorized into four population groups (1) nauplii and meta-nauplii, (2) juvenile Artemia (3) pre-adult Artemia, and (4) adult Artemia and were counted once a week. Results showed that the density of adults, nauplii and meta-nauplii were higher in 100 ppt. The maximum population of pre-adult and juvenile Artemia were found at 50 ppt. The density of adult Artemia increased while density of other categories decreased during culture period. Based on our findings, an inverse relationship between salinity and population of parthenogenetic Artemia were observed. Results indicated that lower salinities are more suitable for population growth of parthenogenetic Artemia.

Identification and ecological survey on macrobenthic bivalves in five sites in the Khark Island were carried out in four seasons during 2010-2011. At each site, three transects including supralittoral, eulittoral and sublittoral zones were selected. The highest and lowest water temperatures were recorded in Summer (35.94 ± 0.28) and in Winter (18.34 ± 0.39) and the highest and lowest salinity were recorded in Winter (44.6 ± 0.14) and Spring (37 ± 0.18), respectively. Maximum and minimum percentages of total organic matter (TOM) was observed in Summer (9.63 ± 0.71) and Winter (3.39 ± 0.15), respectively. Twelve bivalve species belonging to seven families were identified: Barbatia lacerate, Pinctada radiata, Ostrea sp.1, Crossostrea gigas, Sacosstrea cucullata. Diplodonta ravaiyensis, Venus sp.1, Circentia callypyga, Callista sp.1, Gariroseus, Tellina capsoides, Angulus adensis. The maximum and minimum density and distribution have been found in Spring and Summer, respectively. In our study the most frequent bivalve species observed in all seasons was Barbatia lacerate.

Effect of transportation of rainbow trout gametes under moist oxygen packing at 1-2 °c on fertilization was studied. Gametes were transferred in polyethylene bags (20×18cm) containing 0, 25, 50, 75 and 100 % moist oxygen (in its free volume) and ten hours after transfer in a Styrofoam box with thermo gel bags, fertilization were conducted in 25 treatments (in 3 replicates) and fertilized eggs were transferred to an incubator designed for rainbow trout with recirculation system (10°c). Percentage of fertility, eyed eggs, and hatching rate were calculated as an indicator for determination of optimum level of oxygen during transportation. The best results were obtained from fertilization of eggs transported at 100% oxygen and sperm transported at 75% oxygen with 95.01 ± 1.2% fertility, 78±4.21% eyed eggs and 75±3.88% hatching rate which were significant different (p<0/05) compared to the control (treatment without oxygen). As in fish breeding programs, gamete transfer is simpler and inexpensive than brood stock transfer, and hence this method could be applied for short term transferring of rainbow trout gametes as a simple and applicable method.

The effects of five different light regimes on development, survival rate, hatching time and rate of Persian sturgeon (Acipenser persicus) embryos were investigated. Fertilized eggs were exposed to five different light regimes (24L:00D, 12L:12D, 16L:08D, 08L:16L and 00L:24D) until hatching time. Significant differences were observed in blastulation, gastrulation, neurulation stages among treatments. The fungal infection rate was significantly the highest (14.1 ± 1.2) in 12L:12D and the lowest (2.4 ± 0.2) in constant darkness. The highest mortality rate (38.4 ± 1.4) was observed in 12L: 12D, while the lowest (10.9 ± 0.9) was in 16L:08D. Hatching rate was significantly higher in 16L:08D (88.8 ± 3.9) than those in other treatments. Embryos incubated under 12L:12D and 08L:16L hatched earlier (7 days after fertilization), while mass hatching in 16L:08D treatment was observed 9 days after fertilization. Embryos incubated under continuous darkness produced smaller larvae in length, body and yolk sac area. In general, considering the lowest mortality and highest hatching rate of embryos incubated under 16L:08D and absolute darkness, it is suggested that these light regimes are suitable for incubation of Persian sturgeon embryos in terms of mass hatching time, energy access and larval quality.

Microscopic structure of intestine of beluga was studied from hatching until releasing to sea. Larvae were fixed in bouin’s solution, dehydrated and embedded in paraffin wax. Sections of 5-7 μm thick were produced and stained according to standard histological techniques: Hematoxylin-Eosin (HαE) and Periodic Acid Schiff (PAS). One day old larvae possessed a primordial intestine, which is lined by a simple columnar ciliated epithelium. At 3 days after hatching, an oblique furrow of the digestive tube wall started to develop on the dorsal- posterior region of the yolk sac and divided the alimentary canal into two differentiated regions: the future stomach and intermediate intestine. At this time spiral valve started to differentiate. Granules of embryonic pigment accumulated in the spiral valve lumen forming the melanin plug. At 7 days after hatching intermediate gut and spiral gut were lined by a columnar ciliated epithelium. The terminal section of the digestive tract was differentiated into a short rectal duct lined with a cuboidal epithelium. The urinary bladder connected with rectum at this time. At 13 days after hatching the number of vacuoles filled with lipid increase in intermediate gut and spiral gut. Between 17-19 days post hatching beluga larvae have a period of mixed nutrition. At 25 days after hatching cells of intermediate gut showed long microvilli. At 36 days after hatching the number of goblet cells increased in spiral gut. At 43 days after hatching several intestine glands were visible in connective tissue of intermediate gut which was lined by a simple columnar ciliated epithelium. Between 57-75 days after hatching the number and size of mucosal folds increased in intestine. This information may be useful to improve rearing efficiency of beluga and the other sturgeons

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.

The crude protein content and amino acid compositions of muscle from wild and cultured of male and female Acanthopagrus latus were determined by HPLC. There were quantitative differences between individual amino acids in the tissues investigated, depending on the sex and location. It was noted that, among all the samples studied in tissues, sexes and locations, lysine and isoleucine were the principal essential amino acid (EAA) and glutamic acid was mainly for non-essential amino acid (NEAA). Lysine and isoleucine of male muscles had a significantly higher (P<0.05) amount than female muscles. The crude protein content in male and female muscles was not found to be significantly different. Depending on location, the percentages of arginine, leucine, isoleucine, lysine, serine, glycine, alanine and tyrosine were significantly different (P<0.05) in muscles of wild and cultured fish. The wild seabream possessed considerably higher protein content than cultured seabream muscle. The results showed that wild male fish muscle contained a higher (P>0.05) level of EAA than other groups. The results indicate that the Acanthopagrus latus is a healthful component of the human diet.