Journal of Fisheries
Year:2012 | Volume:65 | Issue:1|Papers Count:8

In order to quantify of schooling behavioral responses of Rosy barb (Puntius barbus) subjected to acute decreasing temperature stress monitored by computer- vision system. Four aquaria as duplicate with a density of 30 fish per unit were used for rearing of fish in normal and stress conditions. Some geometric schooling parameters such as average location of center gravity school and distance of coordinate axels X, Y, Z and average of swim speed were used for calculating. Additionally mobility and density of fish school were evaluated by the ‘Projected Mobility Picture’ (PMP) index. Expressed indices for normal temperature condition were compared with acute stress of low temperature. Cortisol was measured from whole body with sampling 6 fish before and after stress. The results showed that schooling behavioral was changed by entering, 8oC water, and expressed indices were different significantly. While average location of center gravity school and distance of coordinate axels X, Y, Z showed intensity fluctuations in all three directions was correlated with spreading and contracting of the school. PMP index showed an accumulation of the school in the outlet area. The average of swim speed of fish school decreased under stress conditions compared to normal conditions (P<0.05). Cortisol levels increased significantly after stress which support behavior parameters (P<0.05).

Tuna fishes are valuable in fisheries. A large amount of tuna fishes which are caught in Persian Gulf and Oman Sea are used for producing fish cans. A lot of skins, left after fish processing that have not any usages. In 1388, one Kg. skin of Thunnus albacare s, Thunnus tonggol and Katsuwonus pelamiswere frizzed and carried to laboratory. Investigations were held on skin sample for extracting oil and gelatin in three replicate. The average of oil and gelatin which were achieved from Thunnus albacare s skin was 10.81%, 7.25%, from Katsuwonus pelamis was 16.73%, 12.09% and from Thunnus tonggol was 16.46%, 14.23% respectively. A significant difference has been seen between the oil and gelatin of Thunnus albacare s and two other fishes. The gelatin, coagulated in 5oC after three hours as well as its solvent obtained in 70oC, after 40 minutes. The amount of gelatin and oil which obtained from these three tuna fishes are significant. Due to some Physical and Chemical features of these two components, may be they can be used in food industry.

The effect of replacing fish meal with soybean meal in diets for red pacu on growth performance, body composition and hematological indices was evaluated in an 8-week trial. Five isonitrogenous and isocaloric diets formulated containing 32.04±0.46 crude proteins and 17.26±0.31 KJ gross energy g-1 diet. The control diet was formulated to contain 50% fish meal, whereas in the other four diets soybean meal was included at 16.5, 33, 49.5 and 66% to replace 25 (SBM25), 50 (SBM50), 75 (SBM75) and 100% (SBM100) of the fish meal protein. One hundred and ninety fish (with average weight 1.8±0.07 g) were randomly distributed into five treatments (each treatment included 3 replicates). Weight gain and specific growth rate in fish fed SBM25 and SBM50 diets were significantly higher than any of other treatments. Feed consumption in fish fed SBM50 diet was significantly higher than other treatments. Feed conversion ratio in fish fed SBM100 diet was significantly higher than fish fed other treatments, while no statistical significant difference was observed between the four other treatments. Whole body composition fish fed SBM50 diet had significantly lower crude protein, lipid, ash and higher moisture compared with other treatments. Fish fed SBM100 diet had a significantly higher hemoglobin and lower hematocrit than other treatments. The results indicated that an economical diet can be formulated using 50 percent soybean meal in red pacu diets without adverse effect on growth performance.

Due to importance of genetic contribution of all broodstocks in artificial propagation of Caspian brown troutSalmo trutta caspius for increasing gene pool in future progeny, effects of milt volume equalization of broodstocks in mixed milt fertilization were assessed. (Ne) was calculated through equal gamete mating of four male and female breeders in two trearments. Assesment of genetic contribution were carried out by polymerase chain reaction using three polymorphic uniqued allel microsattelite loci (Str 591, 73, 58). Parental and progeny genotype were determined by automated ABI PRISM sequencer system and allels were scores by using Gene Mapper software. Pedigree tracing was performed in the basis of exclusion method in FAP program using three polymorphic microsatellite loci in breeders. Ne was calculated as 0.84 and 0.51 in the first and second treatment, respectively which subsequently reduced genetic diversity in alevins significantly (P<0.05). Equalization of milt volume and ova number not only did not result in balanced contribution of breeders, but also produced large variations in contribution to progeny, especially among males. Final results confirmed that real increasing of Ne in artificial breeding of Caspian trout breeders needs serious modifications in fertilization design of breeders in artificial breeding centers in Iran.

Nitrogenous compounds are the main anionic pollutants in recirculating aquaculture systems. Ion exchangers are vastly applied in waste water industry. Negative surface charge? of the zeolites and clays enable them for cation absorptions, however, they do not have any tendency for absorbing anion absorptions. Meanwhile, by modifying surface structure?, they can absorb anions. In the present study, modifications of superficial and layered structures of clays were carried out using the organic compound, tetradecyltrimethylammonium and heat treatment to enable the ion exchangers to absorb the nitrogenous anions from rearing system. Three different ambient temperatures (10, 15 and 20oC) and different pHs (6, 6.5, 7, 7.5 and 8) were used. Results showed that environmental conditions influenced anionic adsorption. Nitrate and nitrite absorption from aquaculture effluent and nitrate from standard solution by two absorbent had significant effect by ambient temperature (P<0.05). In aquaculture effluent, pH did not show any regular effect on nitrite absorption. It was inferred that environmental factors such as temperature, pH, anion concentration, presence of other ions and counter ions are effective on absorptive capability of a given ion. Results showed that modified ion exchangers might be useful for harmful anion absorption from recirculating aquaculture system.

In fish propagation and aquaculture industry, egg incubation period up to hatching is the most critical time. There is scarce information about events happening during this period for Caspian Kutum, which is a very economically important endemic fish in the Caspian Sea. Morphological and histologial developmental changes of Caspian kutum eggs and embryo up to hatching were investigated. Developing eggs from incubator was cleared through the exposure of Acetic acid (1-2%) to study the morphological and histological observation for tissue changes. Early results have shown the cells divisions, archenteron formation and Gaustrolation in second day which result in formation of 3 germinal layers including ectoderm, mesoderm and endoderm. Histological and morphological studies followed blastoderm extending or epibolic expansions which result in notochord and neural plate formation. After that organization started along with neural formation stage and continued till hatching time. Consequently, according to our results, two stages before fertilization and 19 stages after that has been distinguished. Eggs were eyed in fifth day after fertilization and larvae hatched finally as usual in seventh days in 18C.

Interactions between some essential (copper and zinc) and non-essential metals (cadmium and mercury) were examined in muscle and liver tissues of kutum. Fish samples were taken in fishing seasons (February through March 2009) at the southwestern coasts of the Caspian Sea (Guilan province). Mercury (Hg) levels were determined following cold vapor technique and concentrations of Cu, Cd and Zn were measured by atomic absorption (Thermo Electron Corporation, GFS 97) in mg.gr-1 dry body weight. Except for Cd which was recorded only in livers, there was no significant correlation between metal concentrations in liver with concentration of the same metal in muscle tissues. It seems that increase in concentration of Zn is correlated with increase in accumulation of Hg and Cd in livers. Moreover, increase in concentration of Cu in livers resulted in significant increase in Hg levels both in liver and muscles. Based on the obtained results it seems that interactions between metals in fish tissues influence accumulation of essential and toxic metals.

Longtail tuna (Thunnus tonggol) is one of the most important and commercial species in the Persian Gulf and Oman Sea. In order to come up with the responsible fishing pattern, there was a need to identify some of the biological characteristics and population dynamic parameters. Data were collected randomly from six major artisanal fish-landing sites Hassineh, Kong, Bandar Abbas, Salakh, Sirik and Jask in Hormuzgan Province, from April 2010 to March 2011. The mean of fork length was estimated? 63 cm. The growth parameters, L¥, K and t0 were calculated as 112.23 (cm), 0.3 (1/ year) and -0.38 year, respectively and our result showed that T. tonggol grows fast during first two years. These parameters indicated that T. tonggol is found to attain a fork length of 38 cm at the end of first year. The fork length attained at the end of two, three and four year to be 57, 72 and 82 cm, respectively. Growth performance index (Æ) was calculated as 3.6 which was according to other findings in the Indian Ocean.