فصلنامه بوم شناسی آبزیان
سال دوم شماره 2 (پیاپی 202، پاییز 1391)

The eggs of many fresh water fishes become sticky after activation and contact with water. The stickiness property is caused by presence of glycoprotein molecules in outer layer of eggs. In sturgeons the fourth layer of egg (jelly coat) leaks after contacting with water. In teleosts outer zona-radiate is responsible for stickiness. Egg stickiness is important in natural reproduction, whereas eggs can attach to substrate, so brooders can locate the eggs in the best place with the most suitable environmental factors. Also the eggs can be protected by brooders that it strongly raises survival rate. But stickiness is undesirable in hatcheries clumping of sticky eggs results in mortality caused by anoxia and fungal growth. One of the phases in culture of many fresh water fishes, therefore, is to eliminate the egg adhesiveness before incubation. The methods applied for elimination the adhesiveness can be divided into 3 groups: Physical, chemical and enzymatic methods. Physical methods consist of friction the eggs gently with substances such as clay, talc powder and starch. The negative points are lower of hatching rate and time consuming of the process. The most common chemical methods are use of carbamid, tannic acid, milk powder and sodium sulfite (Na2SO3). In enzymatic methods, protease enzymes are administered to eliminate the egg adhesiveness, as the nature of the sticky layer is glycoprotein. Higher hatching rate and quick application are advantageous of this method. Hatching or embryo surviving rate, required time and the expenditure should be noticed for election the best method.

To taxonomic identification and density determination of medusae in Bahrakan area (Persian Gulf), planktonic samples were collected from 6 stations in July, August, October in 2010 and December, February and April in 2011. Sampling was conducted with 300µm mesh size plankton net. Environmental parameters such as salinity, pH, temperature and dissolved oxygen were measured. 5 species were identified. Most abundant species of them were Liriopetetraphylla and its relative frequency was 27.35%. The medusae density was the highest in July and lowest in February.L. indicaisthe first reported in the Iranian waters of the Persian Gulf. The result of Correlation test showed that the temperature has the higher relationship whit density of medusae. Analysis variance test was conducted to study of month impact on medusae abundance. The Shannon index was ranged from 0 to 2.07 and maximum value of this index observed in July.

The improvement of immune system and increasing growth and survival of fishes especially at early stages is important for fish culturists. Considering the effects of herbal immunostimulants on innate immunity and growth of fish, the impacts of dietary Salvia macrosiphon extract on some growth and immunological parameters of fingerlings Pangasianodon hypophthalmus were investigated. Fishwith mean weight of 1.27±0.24 were fed diets supplemented with S. macrosiphon extract at 0 (control group), 150, 300 and 600 mg/kg diet for 45 days. After the feeding trial, fish growth and hematological parameters was analyzed using Duncan test at 95% confidence. Fish growth parameters were not significantly different between treatments at days 15, 30 and 45. All the treatments showed almost 100% of survival. The lowest haematocrit level was observed at control (41.33 ± 4.16%), while the highest (44.56± 2.00%) was at 300 mg/kg diet of Salvia extract. Mean number of WBC and RBC was not different between the treatments. WBC differential count revealed that the highest percentage of neutrophil was in treatment 2, the highest percentage of lymphosyte in treatment 1 and the lowest percentage of monocyte in treatment 3. The mean values of MCV, MCH, MCHC, Hemoglobin, Albumin and total protein had no significant difference between the treatments. The amount of lysozyme was significantly different with the highest amount in treatments 2 and the lowest in treatment 3 (p

This study was conducted to investigate the effect of rearing at differing densities and dietary supplementation with vitamin E on growth indices, survival and carcass composition in fingerling rainbow trout in a 6-week trial. Rainbow trout juveniles with initial body weight of 9.6 ± 0. 69 g at two densities of 50 and 100 pieces per 50 liter were fed two diets with the same protein and fat content. Experimental diets were diet 1 without adding vitamin and diet 2 with adding 600 mg/kg of vitamin E. A total number of 900 rainbow trout juveniles in four treatments, each in three replicates as T50(0) (with the density of 50 and feeding with diet 1), T100(0) (with the density of 100 and feeding with diet 1), T50(E) (with the density of 50 and feeding with diet 2) and T100(E) (with the density of 100 and feeding with diet 2) were randomly distributed. After 6 weeks of feeding, growth performance, feed conversion ratio and viability were significantly differentbetween treatments (P˂0.05). T50(0) and T50(E) had higher weight gain, specific growth rate and viability than T100(0) and T100(E) (P˂0.05). Feed conversion ratio was higher in T100(0) and T100(E) (P˂0.05). Carcass composition was not significantly differentbetween treatments (P˃0.05). The results showed that dietary vitamin E supplementation in rainbow trout juveniles did not have significant effect on growth, feed conversion,survival and carcass composition but density was a key factor in growth, feed conversion ratio and survival.

Some reproductive biology features of Yellowfin Seabream Acanthopagrusl atus including gonadosomatic index, hepatosomatic index, sex ratio, macroscopic and microscopic survey of gonad development, frequency of different maturationstages and absolute and relative fecundity were investigated. Thirty fish per month were sampled during September 2011 to August 2012 in coastal waters of Hormozgan province. The most frequent maturation stage at 4 was in March and April and the highest gonadosomatic index was in April with 7.48 and the lowest value was in August with 0.28. The trend of gonadosomatic index indicated that the spawning season ranges from January to the end of Aprilwith the peak in April and in a batch spawning mechanism. Hepatosomatic index revealed a significant increasing trend from December and reached to the peak in March and April. Considering the sex reversing of male to female in this species, it was confirmed that they are protandric hermaphrodite. Sex ratio showed the value of 2.7 which indicates a significant difference between the number of males and females (P

Black Pomfret (Parastromateus niger) is one of the commercially important pelagic fishes of the southern coasts of Iran. Its stocks are decreasing due to over exploitation, pollution and lack of fishing management programs. In order to assess the population size of this species and to preserve its valuable genetic resources, genetic structure of 32 fish samples was investigated using AFLP markersin Bandar Abbas, Bushehr and Abadan locations from coastal waters of the Persian Gulf. The results showed a total of 205 AFLP bands of which 37 bands were polymorph. The percentage of polymorphic loci in samples of Bandar Abbas (81.08%) was low compared to Bushehr (94.59%) and Abadan samples (86.49%). Nei’s genetic diversity and Shannon’s index were lowest and highest in Bandar Abbas and Bushehr populations, respectively. AMOVA revealed that 86% of genetic variations were within populations and 14% among them. With regard to the amount of Fst (0.09- 0.18) and limited gene flow (1.09- 2.54) between populations, it can be concluded that there is probably three different populations of black Pomfret in Bandar Abbas, Bushehr and Abadan locationsin Persian Gulf.