Iranian Journal of Fisheries Sciences
Year:2009 | Volume:8 | Issue:1|Papers Count:10

Motility of spermatozoa was studied on 12 and 7 specimens of Acipenser persicus and A. stellatus, respectively. The density measured to be 2.22±0.65x109ml-1 in A. persicus and 2.21±0.55x109ml-1 in A. stellatus. Semen samples were diluted with two extenders containing tris 118mM, sucrose 23.4mM, pH=8, egg yolk (20%), dimethyl sulfoxide (15%) and penicillin potassium (500IU/ml) and biociphus extender containing glycerol as a cryoprotectant at a ratio of 1:1 and then transferred to 0.5ml straws and frozen in a computer controlled low temperature apparatus and stored in liquid nitrogen for one week. To study fertilizing ability, the spermatozoa were then used to inseminate eggs after thawing. Mean sperm motility in fresh spermatozoa was 86.6% in A. persicus and 73.75% in A. stellatus which decreased to 32.2% (P<0.001) and 37.5% (P<0.001) in frozen spermatozoa, respectively. Also mean fertilization rate decreased from 90.4% to 30.7% in A. persicus and from 72% to 36.8% in A. stellatus.

The study was conducted with a completely randomized design consisting of four treatments in triplicates. Experimental diets were formulated to contain four different lipid levels (8, 10, 12 and 14%) at constant protein level (46.8%) and different gross energy of 4314, 4417, 4519 and 4622kcal/kg, respectively. Kutum fry (average weight, 203±4mg) were randomly assigned and distributed at a density of 2 fish/l into twelve 80 liter fiberglass tanks equipped with a tap-freshwater system and water temperature of 22-24oC. Fish were fed the experimental diets thrice a day at 10% of body weight for 81 days. Statistical analysis indicated that fish fed the lowest lipid level of 8% showed significant differences (P<0.05) with other treatments. Fish growth, survival, protein and energy retention showed a marked decrease with an increase of dietary lipid level. Crude lipid of carcass composition increased, but ash and moisture decreased with an increase of lipid levels.

In the present study, various developmental stages of Liza aurata oocyte, especially IV and V stages have been described. On the basis of histological investigations, oocyte development in L. aurata comprises immature (I), the early maturing (II), the late maturing (III), mature (IV), ripe (V), and spent (VI) stages. In the stages I and II, nucleus occupied large volume of oocyte. Vacuolization and vitellogenesis appearance started at stage III. Vitellogenesis increased by further growth of oocyte at stage IV and also vacuolization occurred. Zona radiata and follicular cells were more conspicuous at this stage. In the late stage IV, number of vacuoles decreased due to fusing of small vacuoles and nucleoli located on different places of nucleus at this stage. At stage V, oocyte normally possessed one or two oil droplets; nucleus disappeared after migration to animal pole. Recently spawned oocytes were fluid, lemon in color and 779.2µm in diameter. The maximum gonadosomatic index (GSI) value was found at stage V.

This work was carried out to identify decapods of the Bushehr interidal zone, northern coast of the Persian Gulf. Specimens were collected from eight stations along the coast. During this survey, twelve species were identified, including one alpheid shrimp (Alpheus lobidens), three Anomura (Petrolisthes rufescens, Porcellana persica, Clibanarius signatus) and eight Brachyura (Portunus pelagicus, P. sanguinolentus, Eurycarcinus orientalis, Metopograpsus messor, Leptodius exaratus, Pilumnopeus vauquelini, Carpilus convexus and Ocypode rotundata).

Genetic variation and inheritance of randomly amplified polymorphic DNA (RAPD) markers in female grass carp (Ctenopharyngodon idella) and male bighead carp (Hypophthalmichthys nobilis) and their F1 offspring hybrid have been studied. For this purpose, genomic DNA was extracted from muscle tissue according to phenol-chloroform method, and six decamer primers were used for amplifying polymorphic DNA. Results from 77 produced bands showed that all RAPD bands pattern of parents were present in F1 offspring hybrid, which indicated the high influence and dominance of the mentioned markers. The low difference in polymorphisms in used markers between F1 offspring hybrid and parents shows that parents are heterozygous in some loci, which can cause low difference in hybrids of two distinct genera. Although our results revealed that RAPD markers had a suitable efficiency in distinguishing parents from F1 hybrids, genetic diversity of triploid and diploid F1 hybrid were not detected by introduced primers.

An experiment on the polyculture of carps with high valued small indigenous fish species (SIS) pabda (Ompok pabda) and gulsha (Mystus cavasius) was carried out in six months culture period to evaluate the production performance of carp with small indigenous fish pabda (Ompok pabda) and gulsha (Mystus cavasius) in the on-farm condition. Three stocking densities of pabda and gulsha were tested, keeping the carp species combination and stocking density similar. Each stocking density of pabda and gulsha was considered as treatment and replicated thrice. Fingerlings of pabda and gulsha were stocked at the rate of 5,000 (1:1), 7,500 (1:1) and 10,000 (1:1)/ha in treatments 1, 2 and 3, respectively. In all the treatments, carps (Catla catla, Labeo rohita, and Cirrhinus mrigala) were stocked at the rate of 5,000/ha. The production obtained were 2,986±78, 2,580±88 and 2,393±71kg/ha from treatments 1, 2 and 3, respectively, at harvesting. The production levels showed significant difference (P<0.05) among treatments. The contribution of pabda and gulsha to total production was 5.22% in treatment 1, while in treatments 2 and 3 were 7.86 and 9.40%, respectively. It was concluded that pabda and gulsha could be cultured in low input carp polyculture management.

Volatile organic compounds in farmed and wild rohu, Labeo rohita, were extracted by Likens-Nickerson concurrent distillation apparatus. The farmed raised rohu of two weight categories designated as FW1 (1001-1200g) and FW2 (501-700g) were procured from the Fish Seed Hatchery, Faisalabad. Concurrently, wild rohu of two weight categories designated as WW1 (1001-1200g) and WW2 (501-700g) were captured with gillnet from the Trimu Head. Quantitative and qualitative estimation was made by gas chromatography. In farmed and wild L. rohita of the weight group FW1 and WW1, 14 and 6 volatile compounds were extracted, respectively. In weight group FW1, six compounds were identified as 3-methyl-1-butanol, 3-hexene-1-ol, heptanal, 3-octanol, decanal and 2-undecanone. In weight group WW1, out of six compounds three were identified as heptanal, 1-octen-3-ol, 2-nonanone. In weight categories FW2 and WW2, 14 and 13 volatile compounds were detected, respectively. In weight category FW2, out of 14 compounds, 3-hexene-1-ol, heptanal, 3-octanol, 2-undecanone and decanal were identified. In weight category WW2, out of 13 compounds, 7 were identified as 3-methyl-1-butanol, 2-heptanone, heptanal, 3-octanol, 2-nonanone, decanal and 2-undecanone. The analysis of variance for retention time and concentration of volatile compounds showed no significant difference (P>0.05). The correlation coefficient between retention time and concentration was significant (P< 0.05).

Population genetic structure of stellate sturgeon (Acipenser stellatus) in 197 adult specimens from four fishery regions along the Iranian coastline of the southern Caspian Sea was investigated using microsatellite markers. Out of 15 microsatellite primers, 11 loci were produced, in which 10 of them were polymorphic and 1 was monomorph. Totally, 184 alleles were identified and on average 13.1 alleles per locus were found (ranged 8 to 18 alleles). All sampled regions contained unique alleles. Average observed and expected heterozygosity were 0.667 and 0.854, respectively and significant genetic differences between 4 regions were observed (P£0.01). Deviations from Hardy-Weinberg equilibrium were found in most cases. Population differentiation test was modest and significant (P£0.01). Based on FST estimate (P£0.01), more than one population of stellate sturgeon is identified in the south Caspian Sea. Therefore, fishery management for restocking and conservation of gene pool is highly recommended.

Some aspects of the reproductive biology of the Indian squid, Uroteuthis duvauceli, were studied from June 2006 to May 2007. A total of 1200 specimens were collected from approximately 30-80m depths by trawling in 50 stations, of which 360 samples were studied for sex determination and fecundity. The minimum and maximum total and mantle length, and body weight were recorded in December and June, respectively. The highest range of total length (410-420mm), mantle length (150-160mm and body weight (90-100g) were encountered in September. The specimens were composed of 34% male and 66% female (M:F=1:2). This species was found to be more abundant in summer. The minimum and maximum ovary weighs were 2.1g and 7.9g with an average of 4.9g, respectively. These values for nidamental gland weight were 0.70 and 2.61g with an average of 1.6g. The minimum and maximum absolute fecundity were 25510 (in August) and 375600 (in April), respectively. These values for relative fecundity were 5207 (in April) and 867 (in August), respectively. The highest gonadosomatic index (GSI) was in April (14.38) and the lowest was in July (8.63). This squid is, therefore, assumed to be a spring spawner. Minimum and maximum egg diameter were 0.72mm (in August) and 2.5mm (in April), respectively.

Persian sturgeon (Acipenser persicus) is a benthic species occurring primarily on sandy bottoms in the mid and southern Caspian Sea, especially along the shores of Iran (Berg, 1948; Holcik, 1989). The Persian sturgeon in the Caspian Sea is anadromous, with at least eighteen groups that segregate spatially and temporally for spawning. These populations are supported by some spawners, each of which considered to be of two seasonal races and divided into two or four biological groups (Perevaryukha, 2001).