فصلنامه شیلات
سال هفتاد و چهارم شماره 2 (تابستان 1400)

Despite the positive role of rotifers in many hatcheries for feeding the early stages of fish larvae and crustaceans, the lower content of minerals such as selenium (Se, 30 times) and zinc (Zn, 5 times) is considered as one of the disadvantages of this live prey compared to copepods. Therefore, increasing the amount of these nutrients through enrichment is essential. To this end, the present study investigated the effects of the combination of 2 algae Isochrysis aff. galbana and Nannochloropsis oculata enriched with sodium selenite and zinc sulfate on growth and mineral content of rotifer. First, the 1:1 composition of the algae was enriched with a mixture of zinc and selenium salts (each with concentrations of 20, 40 and 80 mg L-1 in algal enrichment medium). The highest number of rotifers (339 ± 11.06 ind mL-1), SGR (± 0.48 ± 0.008 day-1), and the lowest doubling time without any significant difference observed in rotifers fed with algae enriched with 40 mg L-1 of both minerals (p>0.05). However, the highest amount of Zn and Se were observed in those fed with 80 mg L-1 of both minerals. In conclusion, feeding rotifers with Se and Zn enriched algae increased Se and Zn in the rotifers. Thus, microalgae enriched with Se and Zn can be used to feed marine rotifer to meet the nutritional requirements.

In this study, the effect of antioxidant property of green macroalga Caulerpa sp. hot water extract on the prevention of rainbow trout (Oncorhynchus mykiss) viscera oil oxidation at 30°C in a 42-day period, was investigated. The treatments were conducted as a control group (fish oil without preservative), fish oil containing 100 ppm of BHT, and fish oil containing 1000 ppm of aqueous extract of Caulerpa. The results of peroxide value, p-Anisidine value, TOTOX value, and UV270 indicated that the oil containing Caulerpa extract delayed the oxidation compared to the control group, although it showed a relatively lower efficacy compared to the BHT. The Caulerpa treatment showed the highest values of peroxide and TOTOX value on the 35th day which were 38.66 meqo2/kg and 88.24, respectively. While, the BHT treatment showed 30.3 meqo2/kg and 71.70 for peroxide and TOTOX value at the end of the experiment, respectively. Moreover, p-Anisidine showed reached 13.38 and 11.04 mg/kg oil in Caulerpa and BHT treatments at the end of the experiment, respectively. The highest absorbance in 270 nm was 0.9, 0.7, and 0.6 in control, Caulerpa, and BHT treatments, respectively. The results of L* a* b* have not shown a significant difference during the storage period. In general, the results of this study showed that Caulerpa hot water extract as a natural antioxidant delayed the primary spoilage (peroxide value) for 1 week and prevented the second spoilage (p-Anisidine index) of fish oil for up to two weeks and can be offered in the feed and aquaculture industry.

In the present study, the relationship between environmental factors and human activities on the status of coral reef in the southeastern zone of Chabahar Bay (Shahid Beheshti Port) was investigated during the years of 2012-2018. The study methods were included direct observation (diving operations), Line Transect and Coral Watch. The studies showed that the amount of sedimentation in the region had an increasing trend during the sampling years (p < 0.05). The highest and lowest sedimentation rates were measured in summer 2015 and winter 2012, respectively (p < 0.05). The transparency of water during the sampling seasons had a decreasing trend (p < 0.05). The highest and lowest levels of transparency were measured in winter 2013 and summer 2015, respectively (p < 0.05). Water temperature during the sampling period increased from 22.2 ° C in 2012 to 26 ° C in winter 2018 (p < 0.05). The study of human activities in the region showed that during the dredging the sea operation, a lot of mud and silt was deposited in the corals growing area and covered the seabed. After this event, the corals lost their zooxanthella and separated from their seabed after bleaching. It seems that the probable reason for these results is the occurrence of stress due to human activities in the region, which in general has caused a critical situation in the health status of corals in the region.

Aquatic ecosystems have changed dramatically over the last decades. For example, by reducing the water flow in the rivers, organic material would increase in the lower zone of rivers resulted in fluctuating biodiversity of macro-benthic communities. The aim of this study was to determine the changes in macrobenthic diversity in the lower zone (or estuary) of Gharesou river - southeastern Caspian Sea, in where hatchery-reared juvenile fish like Rutilus rutilus (Linnaeus, 1758) and Sturgeon fish (Acipenser sp.) are released for stock enhancement. Sampling was undertaken over five surveys in four sites in the lower zone (or estuary) of river to study the abundance, species richness, and biodiversity indices of macrobenthos. The results of split plot analysis showed that sedimentary organic matter in river litter reduced significantly in the second survey, due to relatively heavy rain fall occurred before second sampling. Whilst, biodiversity indices had no significant differences among surveys (p>0.05), these indices showed significant differences among sampling sites. Species abundance in the third survey increased significantly (p<0.05), related in sharp increment of Tubifex abundance in the fifth site. Rising abundance of Tubifex in the fifth site resulted in significant reduction of diversity indices like Shannon index and inverse-Simpson, and also significant increment of Berger-Parker index, which was probably associated with higher resistance of this species to the hard environmental condition like reduction of water flow in the river. Whilst, diversity indices in the release site for hatchery-reared juvenile was not significantly more (diverse) than the other sites(p>0.05), and also dissolved oxygen and NO3, and NH4 in the release timing had the higher and lower rates, respectively; higher fluctuations of salinity and total dissolved solids in the release site could impact survival of released hatchery reared juvenile. Thus, it is recommended that hatchery reared juveniles being released more far from the estuary towards the upstream.

In the present study, anti-diabetic and antioxidant properties of fucoidan in brown seaweed S. ilicifolium were examined. Initially, pigments, phenolic compounds and low-molecular weight proteins were removed using 80% ethanol and then fucoidan extracted by distilled water at 60 °C for 2h. After fucoidan recovery using 70% ethanol, the fractionation of crude fucoidan was performed by anion-exchange chromatography using DEAE Sepharose FF column. Among crude fucoidan and fractions (F1 and F2), F1 fraction exhibited the highest DPPH radical scavenging (81.28%), ABTS radical scavenging (93.68%) and reducing power activities (0.119 Abs) at 2mg/mL. Besides, F1 fraction exerted the greatest ability to inhibit α-amylase activity (86.16%) at 2mg/mL. Overall, the current findings revealed that fucoidan from S. ilicifolium could be utilized in functional foods as anti-diabetic and antioxidant compounds.

Sexual dimorphism based on morphometric characters and some growth parameters in the Arabian carpet shark, Chiloscyllium arabicum was investigated using 381 collected samples (190 males and 191 females) with the aim of its stock assessment and dynamic population in Persian Gulf for first time. The total length range was between 37.7-70.5 cm (mean of 58.93±6.44 cm) for males and 37.9-75.6 cm (mean of 59.49±8.24 cm) for females. First dorsal fin height was significantly higher in female (P<0.05). Also, all of the morphometric parameters except pre-caudal fin length, pre-second dorsal fin length, pre pelvic-fin length were higher for female sharks (P>0.05). Male and female sharks showed negative and positive allometric growth respectively. Also, the b value of females (3.23) was more than male (2.93) (P<0.05). Asymptotic length (L∞), growth rate (k) and t0 of males were 75.9 cm, 0.93 per year and -0.8; those for females were 75.85 cm, 0.94 per year and -0.79 years respectively. The results derived from data of this study can be useful for determining the strategies to preserve the biodiversity of C. arabicum.

The aim of present study was to evaluate the effect of different extraction methods on physicochemical properties and characterization of chitosan extracted from waste of black tiger shrimp (P. monodon). For this purpose, the extracted chitin from by-products of shrimp processing plant was deacetylated to chitosan, which was soluble in dilute acid. Structural and physicochemical properties of chitosan were evaluated, with FTIR (Fourier infrared spectroscopy) and XRD (X-ray diffraction), and in addition the amount of ash, solubility and degree of deacetylation were evaluated. Crystallization index (%) of chitosan obtained by two different conventional methods was ~ 34% and 36%, respectively. The results showed that the degree of chitosan deacetylation obtained by conventional methods (Hydrocholoric acid and acetic acid) were 94% and 89%, respectively, which did not show much difference. The presence of amine groups in the synthesized chitosan was confirmed by the FTIR spectrum.

This work was conducted to evaluate the morphological variations of eleven species of the genus Alburnoides in Iran using geometric morphometric method. For this purpose, all species were sampled from different stations of six inland water basins. After photographing from their left side, 16 landmark-points were digitized on their images using tpsDig2 software. The data after Procrustes analysis were analyzed by multivariate statistical analysis including PCA, CVA and cluster analysis. Mantel test was used to investigate the relationship between morphological and geographical variations. The results showed significant differences among the studied Alburnoides species in terms of morphology (p < 0.05). Based on the results of PCA, A. samiii and A. nicolausi have higher morphological variations than others. CVA analysis also significantly differentiated A. nicolausi and A. qanati from others. Based on the cluster analysis, Alburnoides species were divided into two groups i.e. A. nicolausi and A. qanati in a cluster and others in another one. The greatest Mahahlanobis distance were obtained between A. holciki and A. nicolausi. The results of this study revealed the better ability of the Landmark-based geometric morphometric technique than that of the traditional one to show morphological differences in the members of the genus Alburnoides.

Assessing the toxic effects of pollutants in the early stages of life of living organism, along with other aspects of aquatic toxicology, helps to better understand toxicity of contaminants and to plan for coping with the conditions created. Aluminum, zinc and copper are some of the trace elements that are increasing in aquatic ecosystems due to human activities. In this study, the acute toxicity of aluminum, copper and zinc were investigated on the survival of the Oreochromis niloticus fish yolk sac larvae and the lethal concentration (LC50-96h) was determined based on the OECD 203 protocol. For this purpose, 200 pieces of larvae with a weight range of 0.0132-0.0156 g and total length of 4.25- 4.75 mm, exposed to different concentrations of aluminum (zero (control), 24, 28.8, 34.56, 41.47, 49.76, 59.71 and 71.65 mg/l), zinc (0 (control), 10, 12, 14.4. 17.28 and 20.73 mg/l) and copper (zero (control), 0.625, 1.25, 2.5, 5 and 10 mg/l) for 96 hours. The mortality was recorded at 24, 48, 72 and 96 hours. The physical and chemical parameters of water were also measured daily. Using probit regression analysis, LC50-96h for aluminum, copper and zinc was 61.839, 1.397 and 14.056 mg/l, respectively. The concentrations were determined at 95% confidence interval in mg / l for aluminum 55.449-67.851, copper 1.157-1.637 and zinc 12.293-16.411. The results, proved that copper was more toxic than zinc and aluminum in tilapia fish larvae.

The antioxidant effects of red algae (Gracilaria corticata) extract on the quality and shelf life of Scomberomorus guttatus fish fillet in three treatments; two concentrations of (A) 300 ppm and (B) 600 ppm of ethanol extract and one control sample immersed in distilled water without any additive was investigated. The samples were stored at refrigerator (4ºC) for 12 days. The measurements were undertaken at 0, 3, 6, 9 and12 days at the beginning of the experiment. The results showed that the total phenolic content and the ability of the red algae extract to preventthe free radicals were 3.74±0.34 mg Gallic acid/g dry weight of extract and 24.7±2.07%, respectively. Generally, thiobarbituric acid (TBA), total volatile base nitrogen (TVN), free fatty acid (FFA) and pH values were significantly increased and lipid content decreased with storage time, whereas the peroxide value )PV( and moisture content increased at the beginning but decreased at the end of the period (p < 0.05). The treatments maintained better quality in comparison to the control group and A treatment had better antioxidant properties and resulted in the longer shelf life of the product.

The efficacy of supplementary diet with a mixture of Bacillus spp. and Lactobacillus spp. probiotics in enhancing water quality, growth performances, serum and skin mucus parameters of Nile tilapia (Oreochromis niloticus) was investigated in four treatments: T1- water exchange system without probiotics; T2, water exchange system with probiotics; T3, zero-exchange biofloc system with probiotics; T4, zero-exchange biofloc system without probiotics, for a period of 90 days. At the end of study, the mean final weight, weight gain, specific growth rate, and feed conversion rates were found significantly (P<0.05) higher in biofloc-based treatments (T3 and T4) versus tanks with water exchange (T1 and T2). The mean values of total ammonia nitrogen (TAN) concentrations and pH were significantly lower in tanks with water exchange (T1 and T2) compared to biofloc treatments (T3 and T4), Meanwhile, probiotic application showed to significantly improve serum immune responses (ACH50 and superoxide dismutase) and skin mucus parameters (total protein, total immunoglobulins, protease activity, lysozyme activity and alkaline phosphatase activity) in both systems. In conclusion, biofloc technology and dietary probiotic administration beneficially enhanced the growth performances as well as serum and skin mucus immune responses of tilapia.

The species of the genus Alosa are very similar to each other in terms of morphology and cannot be identified easily. The present study used geometric morphometric techniques based on outline techniques on scales of the genus Alosa in the southern Caspian Sea, as the simple methods to identify fishes, on the specimens collected in the Southern Caspian Sea, i.e. Parehsar, Anzali, Roodsar and Tonekabon. Three species were found among the samples, i.e. A. braschnikowi, A. caspia and A. kessleri. Some scales from the ventral part of the body (keel) were removed and photographed. The wavelet analysis was performed using shapeR in the software R and canonical principal coordinate analysis were then applied on the scores produced by the wavelet analysis. Also, a Fourier analysis was performed on the outline of the scales followed by pairwise T2 Hotelling tests on the coefficients of the Fourier analysis. Our results indicated that there was a significant difference between A. braschnikowi and A. caspia in shape of the scales.