JOURNAL OF MARINE SCIENCES AND TECHNOLOGY
Year:2011 | Volume:9 | Issue:4|Papers Count:11

The aim of this study were evaluating the effects of crowding and slaughter procedures on imposed stress levels and meat quality in Common carp (Cyprinus carpio). In this work carps imposed to two pre-slaughter crowding (low and high density) and then slaughtered with two killing procedures (asphyxia and hypothermia). Results showed crowding and two different slaughtering methods significantly affected on cortisol, glucose, lactate, chloride, calcium and magnesium levels (P<0.05) but not affected on total protein plasma levels (P>0.05). During 72 h ice storage mean muscle pH in hypothermia groups was higher than asphyxia groups. Rigor mortis reached maximum at 3 h post mortem in asphyxia groups but in hypothermia groups reached maximum after 36 h post mortem. Drip loss in hypothermia groups was higher than asphyxia groups (P<0.05). Refraction index increased during 72 h post mortem and in asphyxia groups was higher than other groups. Overall results of this study revealed that hypothermia in comparison to asphyxia decreased imposed stress to fish and meat quality improved.

This study was conducted to investigate the effect of human chorionic gonadotropin (HCG) and carp pituitary extract (CPE) on the spawning and fertilization parameters in Sander lucioperca. The experimental female fish (1279.33±0.26 g, n=6/group) groups were injected with: group1 (control): physiological saline 0.9%, group 2:4 mg/kg BW CPE, group 3:6 mg/kg BW CPE, group 4:400 IU/kg BW HCG and group 5:700 IU/kg BW HCG. Similarly five groups of experimental male fish (1119.33±0.36 g, n=6/group) were injected using half the dose of female fish groups. The females and males spawned 10-20 h and 28-34 h after injection, respectively. The results showed that, there were significant differences between groups in number of females and males that spawned and fertilization parameters (P<0.05). Results indicate that 400, 700 IU/kg BW HCG and 6 mg/kg BW are suitable for female induction and 350 IU/kg BW HCG for males. There were significant differences in fertilization parameters (P<0.05) between experimental groups. However, no significant difference (P>0.05) in fertilization parameters (fertilization, eyed stage and incubation) was observed between treatment five (700 IU/kg BW HCG) and the natural spawning, but there were significant differences (P<0.05) between treatment 5 and other treatments. Based on the results of the present study, it could be concluded that 400, 700 IU/kg BW HCG and 6 mg/kg BW are suitable for female and 350 IU/kg BW HCG for male induction.

An 8-week feeding trial was conducted in order to investigate the effects of replacement of dietary fish meal by canola meal on growth performance, body composition and ammonia excretion rate (NH3) of the rainbow trout fingerlings. Experimental diets iso-protein (40%) and iso-caloric (3320 cal/g), were formulated with five levels of canola meal consisting of 0, 12, 24, 36 and 48 percent canola, which substituted 0, 25, 50, 75 and 100 percent of fish meal in the control diet, respectively. In each experimental treatment triplicate groups of rainbow trout fingerlings (15.2±2.3 g), were used in a completely randomized design. Fifty fish were assigned to each experimental diet treatment and held in 250 L tank. The results showed that replacement of fish meal by the canola meal up to 75 percent had no negative effects on growth performance. However, complete replacement showed a significance reduction (p>0.05) in all growth parameters. Generally, body composition was affected by level of fish meal replacement, so that 100% replacement of fish meal by canola meal significantly affected dry matter and moisture content of body (p>0.05). It was also revealed that replacement of fish meal by canola meal reduces ammonia excretion by fish, hence reducing environmental impact of aquaculture effluents. Economic efficiency of the diets was also affected by levels of replacement, achieving a highest value at 75% of replacement. In general, results showed that the canola meal has a good replacement potential, and can substitute fish meal in rainbow trout diet up to 75 percent.

Brown trout (Salmo trutta fario) is a vulnerable population of Caspian trout and it exists in most of the freshwater ecosystems of Caspian Sea basin. This study was carried out in fall of 2008 on 70 samples which were collected from Elarm, Absefid, Kamardasht and Delichahi rivers.The weight, length and age of sampled fish ranged from 28.61 to 451.29 (130.74±79.5) g, 142 to 328 (216.9±39.0) mm and 2 to 6 (3.02±1.3) years old, respectively. The results showed that coefficient of vacuity, fullness of feed and relative gut length are 0, 186.3±162.2 and 0.86±0.1, respectively.Studied fish had fed on varied food items consisting of Rhynchobdellida (Glossiphoniidae), Lumbricina (Lumbricidae), Gastropoda (Physidae), Diptera (Chironomidae, Tipulidae, Simulidae, Muscidae, Formidae, Ichneumonidae, Colicoidae and Tabanidae), Coelifera, Ephemeroptera (Baetidae and Heptagenidae), Trichoptera (Sericostomidae, Hydropsychidae, Limnephilidae, Psychomyiidae and Philopotamidae), Lepidoptera, Himeptera (Corixidae), Coleoptera (Hydrophilidae, Dytiscidae, Elmidae and Elateridae), Odonata (Agronidae), Homoptera (Fulgoridae and Aphilidae), Amphipoda (Gammaridae), Arachnida (Hygrobatidae) and brown trout. Chironomidae (88.6%), Simulidae (60.0%), Baetidae (51.4%) and Tipulidae (50.0%) were identified as main food, 13 groups as secondary food and the remaining were considered as accident food items of this fish. Diptera and Coleoptera constituted 91.52% and 6.42% of total numbers of consumed food items, respectively.

The freshwater Cyanobacterium Cylindrospermopsis raciborskii is potentially toxic and widely distributed in tropical and sub-tropical regions. This species is highly abundant throughout the Anzali Lagoon during the months of July and August. The effects of four different photoperiods (L/D 12:12, 10:14, 14:10, 8:16) on growth rates of C. raciborskii were studied. Cylindrospermopsis raciborskii, isolated from water samples collected from the Anzali Lagoon, was cultured in Zehnder 8 media (using Z8 without a nitrogen source) under light intensity of 3000 Lux at 25±2oC. A control group cultured with the main culture medium was also used. This experiment was carried out for 25 days. Inoculants and C. raciborskii cells were counted daily throughout the experiment period using a Neubauer chamber and specific growth rates (SGR) and cell division rates (G) were estimated. The maximum growth rate (8×106±5 cells ml-1) was observed at 12L:12D photoperiod followed by 14L:10D, 10L:14D and 8L:16D. The results obtained in the present study especially with 14L:10D and 12L:12D were in complete agreement with general growth pattern of C. raciborskii observed in warmer months with rather longer daytime in tropical and subtropical areas. The strategy of growth in this species may depend on nitrogen fixation, when other algae were nitrogen limited and also ability to grow in low light intensity and high temperature.

This study was carried out to evaluate the seasonal variations of heavy metal (Ni, Cd, Cu and Pb) concentrations in sediment and 13 dominant seaweed species (3 Chlorophyta, 4 Phaeophyta and 6 Rhodophyta) at six different sites in tidal areas of Bushehr state. Sampling was done during the lowest sea level in 4 seasons from autumn 2008 until summer 2009. All samples (algal and sediment) were digested using nitric acid and analyzed for metals by using Atomic Absorption Spectrophotometr (A.A.S). In this study, metals concentrations (except Cu) showed higher levels compared to other studies from different parts of the Persian Gulf. Metals bioaccumulation was at higher levels during cold season compared to the warm seasons. Seasonal variations of heavy metals were clearly demonstrated by Rhodophyts.

Adaptation to changes in environmental salinities have been widely studied in different euryhaline fish species but there has been less interest in studies on freshwater stenohaline fish adaptation to saline environments. Common carp, Cyprinus carpio is a suitable species to assess the effects of changes in salinities on stenohaline fish. 90 individuals of Common carp (986±0.36 g) were distributed in 6 experimental groups exposed to different salinities of 3, 6, 9, 12 and 15 g/l and a control group. At the end of the experimental period gill tissue from each experimental group was sampled and fixed in 4% paraformaldehyde. Immunolocalization of Na+-K+ ATPase was assayed by monoclonal antibody against α5 subunit of this protein (Hybridoma, USA) in 5 µm sections. Based on the results obtained mitochondria rich cells (MRCs) were present in the epithelium of both lamella and filament but after adaptation to increased salinities these type of epithelial cells (MRCs) were observed only in the epithelium of gill filament and their densities increased as an response to increasing in environmental salinities (P<0.05).

Genetic divergence within and between wild populations of Scomberomorus commerson was assessed using five microsatellite marker (C83Sc, D61Sc, J43Sc, H96Sc, L42Sc). Samples were collected from three locations (Dayyer, Boushehr and Choebdeh ports) in the northern coast of Persian Gulf. 115 specimens of S. commerson were captured to assess genetic differentiation using five markers. Five pairs of microsatellite primer that were used in this study were polymorphic PCR products, which amplified all three populations. Three private alleles in the three loci and one private allele at the one locus were obtained for Dayyer and Boushehr populations, respectively. It was also found that specimens from three sites weren't in Hardy-Weinberg equilibrium (P<0.001). Genetic differentiation measured by the Fst to determin stock structure. Based on AMOVA, the highest Fst=0.057 was observed when specimens from Dayyer were compared with Choebdeh (Nm=4.164). The Lowest Fst=0.025 was observed when specimens from Dayyer zone were compared with specimens of Boushehr zone (Nm=9.818). The results cautiously suggest that adopting a single-stock model and regional shared management are appropriate for sustainable long-term use of this important resource.

The internal wave’s generation process and sound propagation mechanism have been studied, separately. However, the effects of internal waves on sound waves behavior are a study field that has not received any attention in our country. Marine environments are generally density stratified continuously or step-like. Layered structures of oceans affect sound propagation. Taking into consideration that some Iranian waters are density stratified and also have some internal waves that can be used in a sound propagation process for many purposes, it is necessary to study internal waves and sound transmission interaction. This paper attempts to discuss the effects of internal waves on underwater sound propagation using a mathematical model and find out how these processes are inter dependent. The parameters such as sound speed, buoyancy frequency, displacement variance, relative perturbations in sound propagation associated with vertical displacement and horizontal particle velocity, phase & amplitude function, internal waves phase & amplitude spectrum were computed using Caspian sea data. The parabolic approximation was applied in the wave equation to calculate amplitude spectrum density and phase fluctuations of a plane sound wave propagating through a random field of internal waves in the sea.The rate of sound propagation perturbations due to vertical displacement and particle horizontal velocity shows that horizontal displacement is much lower than vertical one. We found out that wave number and vertical displacement increase with increasing depth and decreasing buoyancy frequency. A maximum in buoyancy frequency and sound propagation fluctuations in associate with vertical displacement is observed near water surface which is due to thermocline and there is a minimum in vertical displacement at same place.