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In order to assess the maximum replacement possibility of unicellular green algae with cheap food sources for feeding Artemia, two strains of Artemia urmiana and parthenogenetic Artemia were fed under laboratory condition using wheat bran, soybean meal and 50/50% mixed diet of wheat bran/soybean, each in 12 different concentrations together with different rations of Dunaliella salina for 15 days. The results were compared with those fed only on algae D. salina as control group. At the end of the experiment, control groups in each two strains (with 9.11mm growth and 86.25% survival in A. urmiana and 8.55mm growth and 85% survival in parthenogenetic Artemia) had almost the best condition. In A. urmiana treatments 95.8-88% replacement for algae of wheat bran, treatment 94% replacement for algae of soybean and treatments 97-94% replacement for algae of mixed wheat bran/ soybean showed no significant differences with control in both growth and survival. In parthenogenetic Artemia treatments 94-82% replacement for algae of wheat bran, treatments 91-88% replacement for algae of soybean and treatments 91-82% replacement for algae of mixed wheat bran/soybean showed no significant differences with their control in both growth and survival. According to the results, it seems that single-cell algae and their production requires exorbitant spending and personnel which can be replaced with easily affordable agricultural wastes, without need to specialized staff. *Corresponding author

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In the present study, effects of sub-lethal concentrations of Euphorbia turcomanica extract with ranging from 0.00, 0.0055 (5% of LC50), 0.011 (10% of LC50) and 0.022 (20% of LC50) g/lit were investigated over 30 days on biochemical parameters of Zebra Aphanius (Aphanius dispar). The average (±SE) 24, 48, 72 and 96 LC50 rates of E. turcomanica on fish were 0.28±0.14, 0.19±0.06, 0.14±0.03 and 0.11±0.02 g/lit, respectively. The biochemical parameters including aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), creatine phosphokinase (CK), and alkaline phosphatase (ALP) activities in the liver tissue were measured after 15 and 30 days. Significant changes in AST, ALT, ALP, LDH and CK activities were observed in fish exposed to different concentrations of E. turcomanica extract when compared with control group. The significant increase was determined in AST, LDH and ALP while in ALT and CK, significant decrease was revealed. Also in liver total protein, a significant descending trend related to exposure time was demonstrated. In conclusion, the findings from this study provide basic information about toxicity of E. turcomanica extract on Zabra Aphanius, as well as developing guidelines for evaluating the effects of administration of E. turcomanica derivatives in water.

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Sillaginids are one of the important fishes in coastal waters of Persian Gulf, whose larvae of different species are morphologically very similar to each other and identification of them to species level is very difficult. In this study a total of 4195 Sillaginidae larvae were collected from five inlets (Shif, Lashkari, Ramleh, Dubbeh, Farakeh) and one sampling site in the coastal area of Bushehr Province using a Bongo-net. Morphological and genetic methods were used to identity larvae of this family. The larvae were morphologically divided into two groups, depending on 34 or 38 myomers. The larvae with 34 myomeres were identified as Sillago sihama. To identify larvae with 38 myomers, 12 individuals of postflexion larvae were selected and the morphological characteristic such as number of dorsal and anal fins as well as DNA barcoding of COI were used. According to morphological characteristics, the larvae were divided into two species; Sillago arabica and Sillago attenuata. Genetic studies was done by sequencing of 625 base pair of COI gene. Genetic distances calculated using K2P model between these two species was 18% to 19.7% which indicate that DNA barcoding confirms morphological method and it can be used for identifying younger larvae whose fin rays have not been developed and are unidentifiable with morphological methods.

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This study was carried out to evaluate the effect of replacing Dunaliella salina algae by agricultural by-products (wheat bran, rice bran and wheat/rice bran) and probiotic bacteria Lactobacillus rhamnosus on digestive enzymes activity of Artemia franciscana in a 17-day period post hatch. The study was a 4×2 factorial experiment carried out as a completely randomized design trial consisting of different dietary treatments (combinations of various substitution levels of Dunaliella salina by wheat bran, rice bran and wheat/rice bran along with probiotic Lactobacillus rhamnosus). All treatments were performed in triplicates. At the end of the trial, digestive enzymes activity was assayed. The results revealed that Artemia fed wheat bran without any dietary probiotic supplementation showed significantly higher amylase activity (2.06±0.3μmol maltose mg protein^-1 min^-1) (p<0.05). Treatment fed Dunaliella salina algae and probiotic showed significantly higher alkaine protease activity (7.11±0.87 U mg protein^-1 min^-1) and those fed wheat/rice bran with probiotic had significantly higher lipase activity (0.09±0.005 mmol p-nitrophenol mg protein^-1 min^-1) (p<0.05). It was revealed that dietary probiotic inclusion resulted in decreased amylase activity whilst its effect on the alkaline protease and lipase activities were totally dependent upon the feed ingredients (e.g., simultaneous feeding of artemia by Dunaliella salina algae and probiotic led to higher alkaline protease activity, while receiving probiotic resulted in higher lipase activity in group fed wheat/rice bran). Our results also showed that digestive enzyme profile of Artemia franciscana was responsive to dietary treatment. Conclusively, using wheat/rice bran in artemia pond culture would result in inferior digestive enzymes activity especially alkaline protease and lipase with subsequent effects on nutrient digestion/absorption efficiency and undesirable effects on pond productivity and final product quality.

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The aim of this study was to evaluate the effect of partial replacement of Dunaliella salina algae with wheat and rice bran and Lactobacillus rhamnosus probiotic on growth indices, approximate qualitative factors and the fatty acid profile of Artemia franciscana during 17 days culture period. The present research was designed as a 2×4 factorial experiment in a completely randomized design with 8 treatments and three replicates. The treatments were different in terms of the type of diet (wheat bran, rice bran, mixture of wheat bran, rice bran and Dunaliella salina algae) and also in the probiotic level (0 and 10 percent of daily diet). At the end of experiment the samples were collected to measure the growth parameters, carcass composition, and fatty acid analysis. The results indicated that the Artemia in treatment 2 (85% wheat bran, 15% D. salina) exhibited the highest level of total fat (21%), saturated fatty acids, SFA, (11.90 ± 2.54 mg g^-1 wet tissue), unsaturated fatty acid with one double bond, MUFA, (18.56 ± 3.22 mg g^-1 wet tissue), linoleic acid, LAN, (10.79 ± 1.43 mg g^-1 wet tissue), ash ( 12.15 ± 0.29%) and the lowest food conversion rate, FCR, (1.51 ± 0.03) compared to other treatments (p<0.05). Moreover the treatment 4 (42/5% wheat bran, 42/5% rice bran, 15% D. salina) demonstrated lowest level of specific growth rate (SGR), (27.97 ± 0.05) and dry weight percentage of carcass (7.98 ± 0.08%) among other treatments. The treatment 1 (100% D. salina) showed the lowest ash and the highest FCR and DHA and EPA fatty acids compared to other treatments (p<0.05). Finally we can conclude that wheat bran and combination of wheat bran with probiotic may be the most suitable alternative food to replace D. salina in A. franciscana diet.
 

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The purpose of this study was to evaluate histopathological changes in gills, spleen, liver, kidney and intestine of farmed rainbow trout in four different stations along with Barm Spring (Lordegan, Iran). In this study, at least 15 fish from each farm were captured and following autopsy, sampling was carried out from the gills, liver, spleen and intestine of fish. After tissue sectioning, samples were stained with hematoxylin and eosin. Tissues were studied with a 400X magnification. Gill lamella stick together, gill hyperplasia, exfoliation of gill epithelium, epithelial necrosis and hypertrophy and swelling of gill lamellae, hypertrophy and liver fat degeneration, glomerular and collecting duct of urine degeneration, increase in the lumen space, shrinking the glomerular as well as an increase in melanomacrophage centers (MMC), disorganization of ellipsoids in the spleen, necrosis of epithelial cells, exfoliation of the mucous layer of intestine were the major histopathological alterations observed in the fourth (less than 20% of the group) and the third (a few of fish) group. The results of this study showed that these alterations may be due to an increase in the chemicals in downstream water. Therefore, these histopathological changes could be used as an appropriate biomarker to water quality monitoring.

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One of the comparison methods for evaluating fishing gears efficiencies is based on Catch per Unit Effort (CPUE). In this study, we used three different types of traps for catching oriental river prawn (Macrobrachium nipponense). Capture efficiencies and catch rates of cylindrical pot, opera house trap, and Hokkaido pot were compared with each other during the investigation in Anzali Lagoon. The results indicated that there is a significant difference (P˂0/05) among the amounts of CPUE of cylindrical pot (0.24±0.12 gr), opera house trap (4.17±0.84 gr) and Hokkaido pot (1.58±0.41 gr). There was a significant difference between the results of length frequencies of captured prawns that was trapped by cylindrical pot and opera house trap (P<0.05). Hokkaido, cylindrical and opera house traps were not significantly different from each other for length frequencies. The results indicated that opera house trap was an appropriate fishing gear for catching oriental river prawn because it had higher catch rates and caught prawns with higher length frequencies.
 

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Imbalanced dietary fatty acid profile could influence the performance of larvae. In the present study the effect of various dietary levels of HUFA and PUFA (C₁₈) on histoarchitecture of newly weaned rainbow trout (Oncorhynchus mykiss) larvae were investigated. To this end, various dietary HUFA levels (0, 0.5, 1 and 2 percent) at a fixed dietary PUFA of 20 percent (the first experiment) and various dietary PUFA levels (10, 20, 30 and 40 percent) at fixed dietary HUFA of 8 percent (the second experiment) were created and fed to larvae. The experiments were lasted for six weeks. At the end of the experiments, six fish were randomly taken and the proximal intestine was dissected out and fixed for histological studies. According to lipid epithelial disorganization and cell lifting along with frequency of enterocyte fat stores of proximal intestine of fries, it could be stated when dietary PUFA was fixed at 20 percent (mainly due to replacing dietary fish oil with plant sources), there is no way to prevent such deteriorative histological alterations except increasing dietary HUFA levels up to 2 percent of dietary lipid content. In the second experiment, increasing dietary PUFA to 40 percent of dietary lipid content improved proximal intestine integrity. Furthermore, the lowest goblet cells counts and consequently the highest number of enterocytes, or intestinal absorptive cells, were recorded in treatment 3 and 6. Concludingly, in those groups feeding on diet containing 20 percent PUFA with 2 percent HUFA or 40 percent PUFA with 8 percent HUFA lower lipid vacuoles were present and normal intestinal epithelia were observed.
 
 

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The present investigation was performed to identify the impact effect of development and climate change on the zooplankton assemblage in coastal waters of Bushehr-Delvar region. Sampling was occurred seasonally at depths of less than 10 m using a Bongonet (100 µm) at 10 stations including Jophreh, Jalali, Dastak, Saretol, Helileh, Bandargah, Niroogah, Bushehr, Piazy and Delvar from the summer 2015 to the spring 2016. 40 Zooplanktoon groups belong to 8 Phyla were identified. Crustaceans were the most dominant zooplankton group with the average annual abundance of 37.66% of total zooplankton abundance. The total annual abundance of jellyfish including Salps, Cnidaria and Ctenophora was 16.11% which in comparison with the previous registered data indicated a significant increase over the last four decades in the region. The average annual abundance of zooplankton and Shannon-wiener diversity index were 10577.5±5512.69 /m3 and 2.44±0.218, respectively. The highest and the lowest density of zooplankton were found in Saretol and Delvar stations with the average amounts of 21250±13874/m3 and 4388±3075/m3, respectively. Also, the highest and the lowest density and diversity of zooplankton were observed in the summer and the winter, respectively. Correlation coefficient between the average temperature variation with zooplankton density and Shannon–wiener diversity variations were assessed 0.665 (P<0.34) and 0.91 (P<0.09), respectively. Comparing the results of the present study with the results of the previous investigations indicated that zooplankton assemblage in the coastal waters of Bushehr-Delvar region has been changed under the influence of various natural and human pressures including increased temperature and nutrients which resulted in increasing the density, reducing diversity and changing the species composition of zooplankton.

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The present study focused on ontogeny of digestive enzymes activity namely Pepsin, Trypsin and Chymotrypsin of A. stellatus. Stellate larvae, from the first day of hatch to day 50 of development, were randomly taken for enzyme assay. Specific enzyme activities of Pepsin, Trypsin and Chymotrypsin were determined. The Peptic activity was detected in one-day-old larvae with a sharp raise of enzymatic activity from day 8 post hatch forth, especially during the larval transition to exogenous feedings (p<0.05). The activity of Trypsin in the first day of post hatch was 0.04 U.mg protein^-1 and with an increasing trend, the enzyme exhibited its highest activity on day 8 post hatch (p<0.05). Generally, Tryptic activity was decreasing during the larval ontogeny of A. stellatus. The highest activity of Chymotrypsin was also recorded on the day right after hatching (p<0.05 0.03 U.mg protein^-1). With some rises in the activity of the enzyme on days 15 and 31, however, in general the fish showed a decreasing trend in specific Chymotryptic activity up to day 50-post hatch. Pearson correlation revealed that specific activity of Pepsin of samples were negatively related to alkaline proteolytic enzymes activity (Trypsin and Chymotrypsin) meaning that concomitant with maturation of digestive tract of  the Stellate, the gastric digestion of proteins became dominant (p<0.05). In conclusion, development of stomach in those fish with functional stomach might be indicative of onset of acid Protease digestion, precedence of extracellular digestion to intracellular one and efficient use of dietary protein through post-larval life.
 

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Primary production is an important component in the biological cycle in terms of carbon storage and a key indicator for evaluating of ecosystem function. In this study, net primary production and its components were investigated in the coastal zone of Iranian basin of Caspian Sea during four seasons from 2018 to 2019. In addition, the effective environmental factors on spatial-temporal distributions of net primary production have been studied. As a results, mean (±SD) of Chl-a, euphotic depth (Zeu), active photosynthetic radiation (PAR), maximum primary production per unit of Chl-a (P^B_opt) and daily net primary production (DNPP) were obtained 2.54±3.23 mg/m³, 28.9±6.8m, 40.42±16.84 Einstein/m².day, 5.05±1.11 mgC/mgChl-a.h and 2.04±0.73 gC/m².day. The value of DNPP in the central region was more than the western and eastern regions. It probably is due to effects of wind and waves turbulent on re-suspension of sediment and decrease of light penetration in water column in the western and eastern regions. The seasonal variation of net primary production was in order: autumn>summer>spring> winter. The significant higher NPP in autumn than other seasons (p< 0.05, ANOVA-test), primarily caused by Chl-a and P^B_optic. Based on regression and PCA tests, temporal-spatial changes of DNPP has been significantly affected by the two variables of Chl-a and PB_optic.  In general, the classification of trophic state based on net primary production showed that 52% of the data had trophic states in the range of oligo-mesotroph  and mesotroph (49%) to eutroph (3%) and 48% of the data were in the oligotroph group (mainly in the eastern region).
 

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The aim of this study was to investigate the effect of shrimp farm effluent on the diversity and density of macrobenthic communities of Delwar coast (Bushehr province). For this purpose, sampling was performed by Van Veen Grab sampler (15 x 15 cm²) during the farming period for 8 months (from May to October and two months including April and November as a control) from Delwar beach sediments (6 stations and 3 repetitions for each station). Also, the granularity of bed sediments, soil texture, and total organic matter (TOM) of sediments were measured. In this research, 15 families of benthic invertebrates were identified in 7 orders and 5 categories. Also, the examination of the changes in the detected benthic organisms showed that the maximum density was in April (103±82 N/m²) and the minimum density was in July (70±41 N/m²). Also, station five with 115±40 N/m²and station one with 62±40 N/m²had the highest and lowest density, respectively, and the total density of benthic invertebrates for 8 months of sampling was 15490±581N/m². The results of this research show that the effect of shrimp farming effluents on the abundance of microbial organisms in Delwar coast is remarkable.

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Introduction

During the previous couple of decades, the world aquaculture industry has considerably developed and remained one of the fastest-growing food-producing sectors. The global increase in aquaculture production has resulted in increased worldwide demand for fish oil to meet ever developing aquafeed industry. It has been shown that terrestrial lipid sources including vegetable oils are promising alternatives for dietary fish oil due to their increased production, price stability, and availability. Incorporating vegetable oil instead of fish oil in aquafeed formulation could improve the sustainability of aquaculture development and also increase the profitability of aquaculture industry (Xie et al., 2018; FAO, 2020). The present research was conducted to elucidate the effects of different dietary MUFA contents and LA:ALA ratios, by dietary incorporation of different propositions of vegetable oils including sunflower, linseed, coconut and olive oils instead of fish oil on growth indices and muscle fatty acids profile of Oncorhynchus mykiss fed on a plant-based diet without any marine ingredients.

Methodology

This study was conducted to evaluate the effect of different dietary levels of MUFA and different ratios of linoleic acid (LA) to linolenic acid (ALA) on growth performance and muscle fatty acid profile of rainbow trout fingerlings. 650 juveniles of triploid rainbow trout with an average initial body weight of 14.5 ± 0.17 g were randomly allocated into seven triplicated experimental groups in 300-liter polyethylene tanks. Therefore, seven iso-nitrogenous and iso-lipid experimental diets including diet 1 (55.33, 1.00; dietary MUFA content and LA:ALA ratio), diet 2 (25.30, 1.00), diet 3 (55.13, 2.05), 4 (24.92, 2.03), diet 5 (54.94, 8.06) and diet 6 (24.91, 8.06) and a control diet containing fish oil, diet 7 (33.60, 5.97) were formulated. The basal diet did not contain any fish meal. The experimental fish were fed the diets for 4 months during the first stage of the trial. Afterwards, during the second stage of the trial, all experimental groups were fed diet 7, the basal diet which contained fish oil as the only dietary lipid source for one month. At the end of each stage, the fish were weighed to the nearest 0.1 g to calculate growth indices. Muscle samples were also taken after humanly sacrificing fish for fatty acid profile studies.

Results

At the end of the first four-month feeding period, there was no significant difference among various experimental groups regarding weight gain (WG), relative WG, daily weight gain (DWG), specific growth rate (SGR), and survival rate (p>0.05). Similarly, feeding various experimental groups with diet containing only fish oil as the only dietary lipid source for one month also did not result in any significant differences among the groups (p>0.05). At the end of the first stage, there were no significant differences regarding muscle SFA contents of various experimental groups (p>0.05). Muscle MUFA contents reflected dietary MUFA content so that the highest MUFA proposition was observed in treatment 1 (p<0.05). However, n-6 PUFA and n-6 HUFA contents of fish in treatments 5 and 6 fed diets contained the highest dietary LA:ALA ratio (i.e., 8.0) was the highest (p<0.05). Muscle n-3 HUFA contents of the fish fed diets with lower dietary LA:ALA diet (≤2.0) were considerably higher than treatments 5 and 6 (p<0.05). However, those fish fed with diet 7 showed the highest muscle n-6 HUFA content (p<0.05). At the end of the first experimental period, muscular contents of EPA, DHA and PUFA of all experimental groups were significantly decreased (p<0.05) comparing to those fish fed diet containing fish oil (treatment 7). At the end of the both periods, muscle n-6 PUFA/n-3PUFA was significantly increased in treatment 5 (fish fed diet containing 55% MUFA and LA:ALA ratio of 8) compared to the control group (treatment 7, p<0.05). At the end of the second feeding period, there were no significant differences regarding muscle SFA and PUFA contents among various experimental groups (p>0.05). Similar to the previous stage, muscle MUFA contents of those fish that had previously been fed diets with higher MUFA contents was higher but the difference was milder compared to the first feeding period. Muscle n-3 PUFA and n-3 HUFA contents of fish did not show any differences among various experimental groups (p>0.05). However, muscle C20:4n-6, n-6 PUFA and n-6 HUFA contents still showed significant differences among groups to the extent that treatments 5 and 6 showed the highest propositions (p<0.05). Feeding all experimental groups with the finisher diet containing fish oil could to some extent restore the muscular contents of the aforementioned fatty acids, although muscle DHA content of treatment 5 was significantly lower compared to treatment 7 (p<0.05).

Discussion and conclusions

Our results showed that different vegetable oils blends could replace fish oil in plate-sized rainbow trout feed. Complete replacement of dietary fish oil by such terrestrial oils blends with different MUFA contents and LA:ALA ratios could affect muscle fatty acid profiles of fish which were characterized by high MUFA, ArA, and LA and lower EPA and DHA contents when compared to those fish fed diet containing fish oil. Although, rainbow trout was considerably able to de novo synthesis of EPA and DHA, increasing dietary LA:ALA ratio, i.e., >2.0, resulted in decreased muscle EPA and DHA content revealing that increased dietary LA:ALA ratio might affect liver desaturation and elongation enzymes activity which finally affect muscle fatty acid deposition requiring further studies regarding the enzymes activity and expression. Such decreased EPA and DHA contents warrant further consideration in terms of the nutritional quality of fish fillet for human consumption when replacing dietary fish oils with vegetable oils. In addition, feeding the fish with a finisher diet contained fish oil for a short period could restore the muscular fatty acids profile to improve the nutritional quality of fish. The efficacy of such a feeding strategy was considerably higher in those fish previously been fed diet 2 contained 25% MUFA with LA:ALA ratio of 1.0. However, the complete conclusion warrants more detailed studies in in terms of nutrient digestion and absorption, immune competence and finally reproductive performance of fish.

Conflict of Interest

The authors declare that they have no conflict of interest.

Acknowledgment

We are grateful to the technicians and staff of the Fisheries Department of Natural Resources Faculty and Artemia and Aquaculture Research Institute, Urmia University for their sincere assistance during the experiment.