فصلنامه شیلات
سال شصت و پنجم شماره 3 (پاییز 1391)

The pattern of energy allocation to reproduction varies among the fish species due to their differences in size, habitat, feeding and reproductive strategy. This study surveyed the reproductive energy allocation of leaping grey mullet on the Anzali coast in the province of Guilan, Iran. A total number of 94 leaping grey mullet (20.32±0.2 cm [mean±SE]) were caught in three reproductive states: pre-spawning, spawning, and post-spawning from February to September 2011. The energy content liver, muscle, and ovary were investigated. The energy of liver and muscle changed over the reproductive status. Additionally, leaping grey mullet allocated less energy to reproduction. However, first and second time spawners of leaping grey mullet showed similar energy allocation to reproduction in the spawning season.

Microwave-assisted extraction was applied for extraction of algal extracts from brown algal species (Sargassum angustifolium). Extraction condition consists of three solvents (ethanol, methanol and water), three extraction times and powers of microwave (10min×90W, 20min×180W and 30 min×270W) and three ratios of algae to solvent (1:5, 1:10 and 1:20). All the experimental parameters were applied at three levels according to Taguchi's statistical design. Total phenol contents, individual phenolic compounds, DPPH scavenging activity, ferrous reducing power and total antioxidant activity of the extracts were determined. According to results, the best condition for extraction of antioxidant compounds from S.angustifolium was aqueous extract, ratio of sample to solvent 1 to 20 and 30 minute extraction time and microwave power of 270 W. The TPC, DPPH scavenging activity, FRAP and TAA in optimized treatment are respectively; 2.60 TAE, 1.80 ASAE, %60.04 and 36.45 ASAE. The water extract of Sargassum have phenolic compund such as, gallic Acid (7.33 µg/ml), Protocatechuic acid (29.93 µg/ml) gentistic acid (15.15 µg/ml) and hydroxy benzoic acid (14.61 µg/ml). Results show that this algae was suitable for the extraction of antioxidant compounds.

In this research, composition and abundance of phytoplankton and zooplankton were investigated at earthen ponds of white leg shrimp (Litopenaeus vannamei) in Delvar, Busher. During culture period, variation range of water temperature, salinity, dissolved oxygen and water transparency were 24-32ºC, 45-50 g/L, 3.5-5.5 mg/L and 60-140 cm, respectively. The dominant genera of phytoplankton communities were Navicula, Cosinodiscus, Nitzchia, Rhizosolenia and Pleurosigma from Bacillariophyceae, Peridinium and Ceratium from Dinoflagellates, Oscillatoria from Cyanobacteria, and Nannochloropsis from Chlorophyta. Investigation on zooplankton showed that their community mostly was copepod, rotifer, sergestid, polychaet, and crustacean larvae. The most abundant zooplankton assemblage was copepod which range of calanoid, cyclopoid and harpacticoid were 3-17 ind./L, 0.2-5 ind./L and 0-1 ind./L, respectively. The dominant genera of calanoid and cyclopoid were Acartia and Centropage, and Oithona, respectively, and harpacticoid had only one genus of Euterpina. Abundance of total zooplankton and total copepod had significant differences during culture of L. vannamei. Person’s correlations showed that there was significant correlation between abundance of calanoid and dissolved oxygen (r= -0.43) and salinity (r= -0.54) and also between abundance of cyclopoid and water temperature (r= 0.38) and pH (r= 0.32). In general, total zooplankton abundance had significant positive correlation with dissolved oxygen (r= 0.39) and pH (r= 0.37). Results of Principal Component Analyses (PCA) showed that rotifer abundance, pH and total zooplankton abundance as first factor and salinity and dissolved oxygen as second factor could be used to explain most of variation in zooplankton community in L. vannamei shrimp ponds.

This study was undertaken to evaluate the effects of single sub-lethal copper (Cu) and cadmium (Cd) exposure on biochemical factors of plasma and liver in juveniles beluga sturgeon, Huso huso. A total of 54 fish (weight: 55.4±6.8 g; age: +4 months) were exposed to 20 and 300 µg/l of Cu and Cd in semi-static conditions for 14 days on June (2008), respectively. Then, the effects of these sub-lethal metal concentrations on selected biochemical factors were assessed during 14 days. Results showed that there were no significant differences in plasma glucose, total protein, triglyceride as well as liver protein levels among groups on day 14. Also, metal exposure had significant effects on plasma triiodothyroxine (T3) but not on thyroxine (T4) levels. In contrast, plasma cortisol levels increased significantly compared to the controls only in Cu exposure. No significant differences were observed in liver catalase (CAT) and superoxide dismutase (SOD) activities between experimental groups and controls, but there was significant difference in SOD activities between two metal treatments. This study demonstrated that sub-lethal doses of Cu and Cd were effective on beluga sturgeon. Moreover, it showed that hormonal changes were appropriate biomarkers for Cu exposure in fresh water in beluga sturgeon.

This study was conducted to evaluate the possibility of white leg shrimp (Litopenaeus vannamei) culture twice a year in Nayband Agro-industry complex in 2010. Three earth ponds (0.8 ha) were selected in the farm which had similar conditions in terms of culture system, postlarvae age (PL12) and stocking density (37-38 PL m3). The first period of shrimp culture started from mid April and they were harvested in mid July after 93 days. The second period of culture started in mid August and shrimps were harvested from the ponds in early December after 110 days. Final weight, survival, total production and feed conversion ratio (FCR)in the first period of culture were 13.5 ± 3.12 g, 80 ± 2.27 percent, 3200 ± 27 kg and 1.2 ± 0.09, respectively. These factors were 17.5 ± 3.31 g, 85 ± 2.35 percent, 4500 ± 119 kg and 1.09 ± 0.05 for the second period of culture, respectively. The results of the present study showed that the number of culture days, final weight and survival of shrimps in the second period of culture was higher compared with the first period of culture. Better FCR in the second period of culture showed that the condition of culture in this period is better and more economical than first period of culture. There was 9600 kg shrimp in the twice a year production system that is three times more than common shrimp production system (once a year) in the shrimp farms of southern Iran.

In this study, in order to determine the appropriate time and size to release Salmo trutta caspius, in Kelardasht center conditions, some biometric and physiological parameters were investigated. In this regard, sampling was carried out twice in each season from Parr (one-summer fingerlings) to smolt (two- summer fingerlings) stages in the course of 1 year. The trend of length, weight and condition factor, ions, Osmolality, thyroid hormones (T3, T4) and Cortisol levels of plasma in Freshwater fish and those transferred to Caspian sea Brackish water were measured. Based on the results, weight and length of fishes increased significantly from 8 g and 9.2 cm in autumn to 35.3 g and 14.9 cm in next summer, respectively (p<0.05). Ions and Osmolality levels did not show significant differences among different seasons, but after transfer to Caspian Sea water a significant increase in ions levels was observed. The lowest and highest levels of T3 observed in autumn and summer, respectively, and difference between these seasons were significant. The highest level of T4 was recorded in spring which was significantly different from that value of autumn. Plasma T4 levels showed significant differences between Freshwater and Brackish water in autumn. There were no significant differences among different seasons and Fresh and Brackish water, but the least and highest levels of Cortisol observed in spring and autumn, respectively. Based on these results, it seems that the fish with 20.9 g weight and 12.9 cm length in spring has the most appropriate physiological conditions for release.

The main objective of the present study was qualitative assessment of golden gray mullet stocks by using indicators of overfishing in Iranian waters of the Caspian Sea during a long period (1991-2011). Three fisheries indicators in catch were: 1. percentage of mature fish, with 100% as target; 2. percent of specimens with optimum length, with 100% as target; and 3. percentage of mega-spawners, with 0% as target, and if no upper size limit exists, 30-40% as representative of reasonable stock structure. Over this period, the condition factor of golden gray mullet showed decreasing trends, declined from 1.16 in 1993-1994 to 1.01 in 2010-2011. The range of length with optimum yield was between 31.8-38.8 cm, using biological parameters. The mega-spawner measured as fish a size larger than 38.8 cm. According to these three indicators, the percentage of mature (fork length>28 cm), optimum size and mega-spawners were ranged between 58.6%-88.4%, 26.4%-47.6% and 6.8%-29.0%, and were averaged (±S.D) 76.0%±6.78, 36.1%±5.44 and 18.9%±5.71, respectively. Therefore, for conservation and revitalization of golden gray mullet in the Caspian Sea, the target would be to all (100%) fish spawn at least once, using bigger mesh size in sac (e.g. 33 mm, during whole fishing season), also, the aim would be to implement a fishing strategy that result no (0%) mega-spawners being caught, and the main catch focus on optimum length. Also, the start of the fishing season should be delayed in order for stocks to complete their spawning.

The aim of the peresent study was to find the optimum weaning time to shift pikeperch larvae feeding from live food to the artificial feed. In this experiment, pikeperch larvae were fed with seived pond zooplankton (mainly rotifers) and Artemia nauplii from the first feeding day to day 16 of post-hatching. then three weaning times were used on day 16 (W16), day 22 (W22), and day 28 (W28) of post-hatching, and compared with a control group (fed on only live food). According to the obtained results, the best growth (mean weight gain = 152. 8 mg) and the highest survival rate (61.6%) were found in larvae fed only on live food during the whole period of rearing. The lowest weight gain (28 mg) and the lowest survival rate (13.3%) were observed in larvae weaned at day 16 post-hatching. From the biological point of view (growth parameters), the most suitable method of pikeperch larvae rearing was exclusively with live food throughout the experiment (0-34 days), however, the results of growth performance in larvae weaned at day 28 post-hatching was noticeable.

In this study brown trout Salmo trutta populations in Mardagh and Liqvan Rivers from the West and East Azerbaijan provinces (Iran) were studied using 12 microsatellite loci. In total 52 fish from the mentioned populations and 45 fish from Babolrood and Haraz Rivers were analyzed. According to the analysis of the private alleles, Hardy-Weinberg equilibrium test and genetic differentiation between the populations (Fst=0.04) and based on other reports, it can be concluded that during the years 2004-2007, there should be at least a case of brown trout transfer from Mardagh to Liqvan River. In both the Liqvan and Mardagh Rivers private alleles specific to each river were observed, indicating that indigenous brown trout were existent in Liqvan River prior to fish transfer.

In this research, sludge characterization and rates of mineralization was evaluated in different sizes of rainbow trout (Oncorhynchus mykiss) in the culture systems. Four weight groups of fish (20±3; 50±5; 100±9; 200±10 gr) in triplicates were introduced and cultured in the experimental units (200 liter tanks) for a three day period. The fish were fed with a commercial dry feed pellete (Faradaneh Co.). The rates of mineralization due to the effect of natural flora (microorganisms) of bacteria on the produced sludge, was detected. In this respect, the fish captured and remainder sludge and the rate of macro and microelements recorded in all the treatments during a 7 day period. Concentration of TAN (Total Ammonia Nitrogen) and NO3-, shwoed significant differences among all treatments within initial day until the third day (p<0.05). Concentration of total phosphorous (TP) increased and showed significant differences among treatments after the first stage of the experiment (three days) (p<0.05). EC and total hardness showed significant differences among the treatments after the first stage of the experiment as well (p<0.05). It was concluded that, bacterial mineralization of sludge and organic matter had larger effect at the first three days, in comparison with after harvest of fishes as well.