Journal of Aquaculture Development
Year:2020 | Volume:14 | Issue:1 |Papers Count:10

Feeding fish is one of the most important factors in aquatic nutrition. Regarding the importance of nutrition in aquaculture, many studies have been done; However, few studies have been conducted on the effect of different feeding rates on reproductive activity of fish. This experiment was conducted to determine the effect of feeding rates on reproductive performance of the swordtail (Xiphophorus helleri). In this study, 180 fish pieces of about 2. 5 months of swine tail (45 males and 135 females) were distributed in 15 aquariums with dimensions of 60 * 40 * 30 centimeters including 5 treatments and 3 replicates and distributed under the same conditions. Fish in different treatments with different percentages (1, 2, 3, 4 and 5% based on body weight) Three times a day, they were fed with food (made by the Biomar company of France) for four months. Reproductive performance (time of sexual examination, production time of the first larvae and the number of larvae received) were evaluated. The results of the experiment showed that the production of the first larva was related to the treatment of 3% and the number of larvae produced in T3 treatment was significantly different than other treatments (P <0. 05) and had the highest number of larvae. In addition, the lowest number of larvae was recorded in T1 treatment, however, there was no significant difference with T2 treatment (P <0. 05).

In the present study, the adaptation of Asian sea bass (lates calcarifer) was investigated in fresh water using physiological parameters of osmoregulation including: the plasma levels of thyroid hormones and cortisol, gill Na+/ K+-ATPase activity and plasma concentrations of sodium and chloride. For this purpose, 60 fish were distributed in three 300 L tanks with a density of 20 fish per tank. Fish sampling was done in two steps: Step 1) Before adaptation in freshwater (sea water stage) and step 2) After 24 hours adaptation in fresh water. According to the results, the activity of Na+/ K+-ATPase significantly increased during the period of adaptation in fresh water (p<0. 05). Thyroid hormones showed a significant increase during 24 adaptation in fresh water (p<0. 05). Also, cortisol levels did not change during the adaptation period (p>0. 05). The concentration of sodium and chlorine ions significantly decreased during the adaptation period in fresh water (p<0. 05). Additionally, 10% mortality was observed during the period of adaptation. The results of this study showed that Asian sea bass can be adapted to freshwater shock. However, it seems that the proper ion balance obtains at adaptation period more than 24 h.

In recent years, cage aquaculture has been introduced as modern technology in the world. Although the use of cages for fish’ s holding and transporting for short periods can return two centuries ago in Asian, commercial cage aquaculture was pioneered in Norway in the 1970s and 1980s. Today, due to population growth, climate change and more attention to the productivity of water use in the aquaculture, The focus has been on dense systems. The presence of various water sources such as lakes, reservoirs, rivers and coastal, The use of cage technologies can contribute to aquaculture development. According to FAO's 2016 statistic, cage aquaculture accounts for 35% of the world's total aquaculture production. Also according to Iranian fishery organization statistics in 1395, cage aquaculture production was 10162 tons Equal to 2. 2 percent of the total aquaculture production in Iran. The success and development of cage aquaculture depends on several factors. To develop sustainable, industries need to recognize the challenge, the advantages and disadvantages. The marketing, increasing private sector investment and government supervision are challenges that need to be considered in the cage aquaculture development.

In this study the effect of non alkohalic beer concentrate was investigated on the expression of growth hormone (GH), insulin growth factor1 (IGF1) genes and skin mucus immunity (Ig and ALP) in common carp. 180 pieces of common carp with average weight of 12. 5 ± 2 g, were fed experimental diets supplemented with different levels of non alkohalic beer concentrate (0 [control], 0. 5, 1 and 2%) (4 treatments and 3 replicates) for 8 weeks. At the end of feeding trial, RNA was extracted from brain and liver and cDNA synthesized using Suprime Script RTase and expression of growth related genes, GH (brain) and IGF-1(liver), were assessed using Real-time PCR. Mucosal immune indices (ALP and Ig) were measured using kit. The study of growth related genes in brain indicated significant increase of GH gene in fish fed non alkohalic beer concentrate compared to control (P<0. 05). However, the results of IGF1 gene expression revealed no significant difference among treatments (P>0. 05). The skin mucus ALP activity and Ig level in fish fed non alkohalic beer concentrate were significantly higher than those in control group (P<0. 05). According to these results, administration of non alkohalic beer concentrate can improve immunity and growth in common carp.

This research was conducted in autumn and winter of 2016 in Shahid Motahary Coldwater Fishes Genetic and Breeding Research Center. The purpose of this study was to evaluate the effect of Huwa-San TR-50 solution on controlling rainbow trout fungus contamination at incubation stage and comparing its effects with malachite green and formalin. To do this, 27 Californian traphs were used in 9 treatments and 3 replicates, and 700 eggs of rainbow trout were stoked in each traph. 5 treatments with different concentrations (50, 100, 200, 300 and 500 ppm) of Huwa-San TR-50 solution, one treatment with malachite green (2ppm) and one treatment with formalin (1000ppm), by bathing for 30 minutes were disinfected; a positive control (contaminated with fungi and without medication) and a negative control (non-infected with fungi and without medication) were also considered. The results showed that solution of 300 ppm Huwa-San TR-50 was suitable concentration for disinfection of eggs. Percentage of eyed egg and hatching at higher doses and lower than 300 ppm Huwa-San TR-50 showed a decreasing trend.

In this research, it was used salt supplement in feed of Rutilus kutum juveniles (about one gram) in the freshwater environment by aim of changes of gill and kidney tissue for stimulating osmotic regulation system. The purpose of this research, was to improve survival rate of juveniles’ fish during move time to brackish water. It was initial average weight for Juveniles’ fish 0. 91± 0. 01 g (mean± SE). Experiments carried out in two phases. In step one, the fish were put for 15 days in freshwater and they were fed with commercial diet containing NaCl supplement in four treatments (control without NaCl supplement, 5, 7 and 10 percent). The each treatment had three replications. In the second step, the fish were moved to brackish water of Caspian Sea (12. 5 psu) and they were fed for 28 days with a commercial diet (without NaCl supplement). The results in step one showed that it was not changed renal tissue in all treatments. But, it was observed significant difference between size of glomerulus and renal tubules between freshwater and brackish water environments (between step one and two), (P<0. 05). In steps one, there were observed gill accessory cells in all treatments that fed salt supplements. At the end of the second step, number of gill chloride cells in control treatment was lower than other treatments that it fed in ones step with salt supplementation (P<0. 05). The results showed that it was survival rate in fish fed dietary supplements of sodium chloride 5% more than other treatments (P<0. 05). Therefore, feed low level salt supplement in diet of Rutilus Kutum fingerlings in freshwater is fish physiologic provocation against environmental saline water.

Due to the sharp decrease or lack of feeding of carp during winter and the effects of malnutrition on fish health, the aim of the study was to determine the effect of overwintering on hematological and some sero-immunological parameters of cultivated common carp (Cyprinus carpio). The samples were gathered two times (March and May) from one the earth pond in Behshar. Every time, 30 fish were capture and their average weight were 152. 3 ± 14. 7 and 181. 2 ± 13. 2 g respectively. In this study, the amount of red and white blood cells, hemoglobin, hematocrit, mean cell volume (MCV), mean cell hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), glucose, cholesterol, triglyceride, total protein, albumin, IgM, alkaline phosphatase (ALP), certain phosphokinase (CPK) and serum lysozyme activity were evaluated. The results showed that the number of red and white blood cells, glucose hematocrit, total serum protein, alkaline phosphatase (ALP), certain phosphokinase (CPK), cholesterol, triglyceride, IgM and lysozyme activity were significantly lower in the samples were taken in March. Also, there was no significant difference between the levels of hemoglobin, albumin, MCV, MCH and MCHC despite numerical difference between two the groups. The results of this study showed that the decrease in blood, serum and immune parameters during winter were caused by decreased metabolism and lack of carp nutrition. It is inevitable and this could be one of the possible causes of winter mortality and increase their susceptibility to some infectious diseases. Therefore, it is recommended that breeders use high-quality diets and immunostimulants supplements to increase their hemato-serological parameters and immunity, by increasing the temperature and starting feeding fish actively.

Abstract Beside knowledge on primary production and food webs, species composition and density of phytoplankton in shrimp culture ponds are an important issue in relation with shrimp diets and production in the ponds. In order to provide an updated information about phytoplankton community in shrimp culture ponds, this study was carried out to determine species composition and abundance of phytoplanktons in shrimp culture ponds of Gomishan (South East Caspian Sea) at three defined points in each pond (near the inlet, middle, near the outlet) on a monthly basis sampling from May to October 2016. Sampling was performed using 1 liter volumes in surface water ponds. The results showed that there are a total of 23 genus phytoplankton belonging to 6 phylum. The dominant genus were Nitzschia from Bacillariophyta, Peridinium from Dinophyta, Aphanotece and Anabena from Cyanophyta and Chlamydomonas from Chlorophyta. Generally the dominant genus included 66% of total abundance of phytoplankton community. The highest average density observed was Dinophyta phylum with 50%, and the lowest was Cryptophyta and Euglenophyta phylums with 1% of total phytoplankton abundance. The both highest and lowest abundance of phytopanktons were observed in the intermediate ponds.

Feeds is major of current values in intensive fish and other aquatic animal culture (30-60% approximately). Therefore, aquaculture scientists have been attempted to find feed costs decreasing approaches. Earth worm (Eisenia fetida) is one of the most important commercial species. It can use in fish farming especially rainbow trout farms. Therefore, the study was conducted to investigate E. fetida effects on the growth and hematological indices in rainbow trout. For this purpose, juvenile fish with an average weight of 10 g were evaluated for 10 weeks. The experiment carried out with 4 treatments (each treatment includes 90 fish). Fish were feeds by 0, 10, 20 and 30 percentages of feeds by earth worm. Results showed any differences between the groups.

Rainbow trout farms released always a large amount of organic matter into the environment, resulting in environmental contamination. If these waste can be used as a food source for the production of a secondary organism such as Nereis diversicolor, in addition to increasing production, it will reduce the volume of contamination originating from fish farms. In this regard, determining the nutritional value of the faeces produced and its effect on the growth performance of the worms feeding them compared with a standard commercial feed provides the possibility of better management to achieve maximum productivity and sustainable aquaculture. In this research, two treatments in three replicates with the density of 1000 worm/m2 were examined during 60 days under the same conditions (temperature 17. 71 ± 0. 6° C, oxygen 7. 77 ± 0. 16 mg / L, pH 7. 96 ± 0. 09). The first treatment was fed with faeces produced by rainbow trout and the second treatment was fed with a commercial feed of trout (Faradaneh). The results showed that worms fed with fish food had better conditions in terms of growth performance during 60 days in all growth and survival factors than worms fed with fish faeces. The main fatty acids in both groups of worms were Palmitic acid (C16: 0), Oleic acid (C18: 1 n9c), and Linoleic acid (C18: 2 n6c). Also, the ratio of DHA / EPA in both groups of worms was less than one (the first treatment was 0. 40 ± 0. 22% and the second treatment was 0. 59 ± 0. 18%). In general, the amount of main fatty acids, DHA, EPA and DHA / EPA ratio in worm samples fed with fish food were higher than those fed with fish faeces. Therefore, there is the possibility of breeding polychaete Nereis diversicolor by rainbow trout faeces, but they need more time for breeding to achieve proper growth. It is important because there is no cost for feeding.