ALBERT

Description: Four experiments were conducted to study of production meat in reared beluga (Huso huso) with different diets. In the first experiment, A 19-week feeding trial was conducted to evaluate dehulled soybean meal (DHSM) as a fish meal (FM) replacer in juvenile beluga, of initial body weight 8.25 ± 0.08 g (mean ± SD) in triplicate groups, fed six isoenergetic (20.1 mJ kg-1) and isoproteic (45% crude protein) diets, resulting in 5%, 10%, 15%, 20% and 25% of fish meal protein being replaced by soybean protein. Growth performance was reduced significantly with the increasing of DHSM in the diets in the present study. In the next stage, triplicate groups of 315 fish averaging 300.25 ± 10.28 g (mean ± SD) were fed one of seven experimental diets for 14 weeks. Weight gain (WG), specific growth rate (SGR), feed effeciency (FE), protein efficiency of retio (PER) of fish fed 5%, 10% and 15% of soybean protein diets were significantly higher than those of fish fed 20%, 25% and 30% diets. Whole body protein, lipid, moisture content were unaffected among different treatments (P 〉 0.05). In the second experiment, A 2 × 4 factorial design was used to evaluate the dietary lysine and to determine the optimum dietary L-carnitine in sub-yearling beluga, reared in the indoor system. Twelve experimental diets were formulated and prepared to contain four lysine levels (0.75, 1.5, 2.25 and 4% diet) and two L-carnitine levels (300 and 600 mg/kg diet) at each lysine level. Fish averaging 23 ± 0.5 (mean±SD) were fed one of the experimental diets for 10 weeks. At the end of the experimental period, there were significant lysine and Lcarnitine effects (P 〈0.05) on growth performance and feed conversation ratio (FCR). These results may indicate that, weight gain (WG), FCR and protein efficiency ratio (PER) in fish fed diet containing 3% lysine and 600 mg L-carnitine/kg diet were significantly higher than those of fish fed control diet (P 〈 0.05). There were no significan dietary lysine and L-carnitine effects on glucose, cholesterol and haemoglobin (Hb) concentration, of fish fed different levels of lysine with 300 mg L-carnitine/kg diet, however, Hb concentration in fish fed diet containing 2.25% lysine and 600 mg L-carnitine/kg diet were significantly higher than those of fish fed control diet (P 〈 0.05). These results may indicate that the optimum lysine and the L-carnitine levels could be 2.25-3% and 600 mg L-carnitine, respectively in begga (8-300 4g), based on growth performance, feed utilization and hematological parameters. In the thired experiment, a study was conducted to evaluate the effects of dietary betafine and metionine interaction on the growth, feed efficiency, carcass composition and hematological index in juvenile beluga. Thirteen diets were formulated to contain four dietary metionine levels (0.5, 1, 1.5 and 2%), betafine (0.5, 1, 1.5 and 2%) with equal ratio of metionine and betafine (0.5: 0.5, 1: 1, 1.5: 1.5 and 2: 2% diet) were fed to juvenile beluga (23± 0.5 g) in triplicate groups for 12 weeks in a indoor system. The results showed that no significant (P〉 0.05) differences were found in growth performance and feed utilization among the dietary betafine and metionine concentrations in beluga. Hb concentration of fish fed control, 1 and 1.5% metionine were significantly higher than those of fish fed the other diets. FCR of fish was significantly improved by dietary metionine and betafine. FCR was lower (P 〈 0.05) in fish fed equal ratio of metionine and betafine (2: 2) diets than those in fish fed control diet. Based on above results, it is recommended that the diet for juvenile beluga, Huso huso (8-300g), should contain equal ratio of metionine and betafine (1.5: 1.5) diet, corresponding to 5.95 g/100 g of dietary protein for optimum growth, efficient feed utilization and whole-body protein content. A 17-week feeding trial was carried out to evaluate the effects of dietary L-carnitine level in beluga, Huso huso. A total of fish averaging 1247 ± 15.6 g (mean ± SD) were randomly distributed into 18 fibreglass tanks, and each tank holding 10 fish was then randomly assigned to one of three replicates of six diets with 50, 150, 350, 650, 950 and 1250 mg L-carnitine kg-1 diet. At the end of 17 weeks of feeding trial, average weight gain (WG), feed efficiency (FE), protein efficiency ratio (PER) and condition factor (CF) of fish fed 350 mg kg-1 diet were significantly (P 〈 0.05) higher than those of fish fed 50, 150, 950 and 1250 mg kg-1 diets. WG, FE, PER and CF of beluga fed 650 mg kg-1 diet were also significantly higher than those of fish fed 50, 950 and 1250 mg kg-1 diets. Whole body and muscle protein were significantly improved by the elevation of dietary L-carnitine level up to 350 mg kg-1. Liver superoxide dismutase and glutathione peroxidase activities of fish fed 350 and 650 mg kg _1 diets were significantly higher than those of fish fed 50, 950 and 1250 mg kg-1 diets. The dietary Lcarnitine level of 350–650 mg kg-1 diet could improve growth performance, feed utilization, protein-sparing effects of lipid, antioxidant defence system and reproductive success. Polynomial regression of WG suggested that the optimum dietary L-carnitine level was 480 mg kg-1 diet. Therefore, these results may indicate that the optimum dietary L-carnitine could be higher than 350 but 〈650 mg kg-1 diet in beluga reared in intensive culture conditions.

Description: Iranian Fisheries Science Research Institute

Description: Published

Description: Iranian Fisheries Science Research Institute

Description: Published

Description: Growth experiments were designed and conducted in several phases in order to determine the most suitable starter diet, to determine the effects of different levels of protein and energy and also to determine the effects of different ratios of carbohydrate to fat on growth and body composition in farmed Huso huso from the larval stage up to the marketing stage. Phase one Growth experiments were conducted in a random statistical design to compare growth trends in H. huso larvae (mean weight 105.02 ± 0,02 mg) without being adapted to formulated diets. Experiments were conducted in fibreglass tanks (500 litre capacity) under similar culture conditions. Four replicates were run for each experiment. Larvae were fed four types of formulated diets (Diet A=100 % formulated diet produced in the International sturgeon Research Institute, Diet B=formulated diet imported from Holland, Diet C= formulated diet imported from France, Diet D= a mixture of Diet A + 10% gammarus) 8 times a day to satiation for a period of 49 days. The results obtained were compared with those obtained for the control group that was fed live food (Daphnia and Artemia). Mean water temperature during the experimental period was 18.52 ± 0.48 °C and mean dissolved oxygen was 7.35 ± 0.18 mg/l. The first signs of food granules were observed in the guts of the larvae after 12 h of the first feeding. All experimental groups were adapted to granulated diets on day 3 to day 5. In the beginning of the experimental period the larvae showed a no normal distribution (P 0.05) in terms of weight and length. However significant differences were observed in the end of the experimental period among the different groups studied in terms of growth, specific growth rate and food efficiency (P 0.05). Growth in group B and D were significantly higher than that in other groups except for the control group (P 0.05). It may thus be concluded that the olfactory organs of larvae took to Diet B (may be due to its composition) and to the diet D (because of its odour, texture and suitable flavour) more readily than other diets. At the end of the experimental period, maximum survival (98%) belonged to the control group. Survival rate in Group B and Group D was 90 % and 86.5%, respectively (P 0.05). Minimum survival belonged to fish fed Diet A (29.7%) and Diet C (45.5%). With regard to the adaptability of larvae to formulated diets, survival rates and growth and development in larvae we may conclude that the effects of different formulated diets on growth in larvae can be conducted on larvae with a mean body weight between 100 to 120 mg. In this weight class the digestive system and olfactory organ are fully developed and play a vital role in searching for food particles.

Description: Four experiments were conducted to study of production meat in reared beluga (Huso huso) with different diets. In the first experiment, A 19-week feeding trial was conducted to evaluate dehulled soybean meal (DHSM) as a fish meal (FM) replacer in juvenile beluga, of initial body weight 8.25±0.08 g (mean±SD) in triplicate groups, fed six isoenergetic (20.1 mJ kg^-1) and isoproteic (45% crude protein) diets, resulting in 5%, 10%, 15%, 20% and 25% of fish meal protein being replaced by soybean protein. Growth performance was reduced significantly with the increasing of DHSM in the diets in the present study. In the next stage, triplicate groups of 315 fish averaging 300.25 ± 10.28 g (mean ± SD) were fed one of seven experimental diets for 14 weeks. Weight gain (WG), specific growth rate (SGR), feed effeciency (FE), protein efficiency of retio (PER) of fish fed 5%, 10% and 15% of soybean protein diets were significantly higher than those of fish fed 20%, 25% and 30% diets. Whole body protein, lipid, moisture content were unaffected among different treatments (P 〉 0.05). In the second experiment, A 2 × 4 factorial design was used to evaluate the dietary lysine and to determine the optimum dietary L-carnitine in sub-yearling beluga, reared in the indoor system. Twelve experimental diets were formulated and prepared to contain four lysine levels (0.75, 1.5, 2.25 and 4% diet) and two L-carnitine levels (300 and 600 mg/kg diet) at each lysine level. Fish averaging 23 ± 0.5 (mean±SD) were fed one of the experimental diets for 10 weeks. At the end of the experimental period, there were significant lysine and Lcarnitine effects (P 〈0.05) on growth performance and feed conversation ratio (FCR). These results may indicate that, weight gain (WG), FCR and protein efficiency ratio (PER) in fish fed diet containing 3% lysine and 600 mg L-carnitine/kg diet were significantly higher than those of fish fed control diet (P 〈 0.05). There were no significan dietary lysine and L-carnitine effects on glucose, cholesterol and haemoglobin (Hb) concentration, of fish fed different levels of lysine with 300 mg L-carnitine/kg diet, however, Hb concentration in fish fed diet containing 2.25% lysine and 600 mg L-carnitine/kg diet were significantly higher than those of fish fed control diet (P 〈 0.05). These results may indicate that the optimum lysine and the L-carnitine levels could be 2.25-3% and 600 mg L-carnitine, respectively in begga (8-300 4g), based on growth performance, feed utilization and hematological parameters. In the thired experiment, a study was conducted to evaluate the effects of dietary betafine and metionine interaction on the growth, feed efficiency, carcass composition and hematological index in juvenile beluga. Thirteen diets were formulated to contain four dietary metionine levels (0.5, 1, 1.5 and 2%), betafine (0.5, 1, 1.5 and 2%) with equal ratio of metionine and betafine (0.5: 0.5, 1: 1, 1.5: 1.5 and 2: 2% diet) were fed to juvenile beluga (23± 0.5 g) in triplicate groups for 12 weeks in a indoor system. The results showed that no significant (P〉 0.05) differences were found in growth performance and feed utilization among the dietary betafine and metionine concentrations in beluga. Hb concentration of fish fed control, 1 and 1.5% metionine were significantly higher than those of fish fed the other diets. FCR of fish was significantly improved by dietary metionine and betafine. FCR was lower (P 〈 0.05) in fish fed equal ratio of metionine and betafine (2: 2) diets than those in fish fed control diet. Based on above results, it is recommended that the diet for juvenile beluga, Huso huso (8-300g), should contain equal ratio of metionine and betafine (1.5: 1.5) diet, corresponding to 5.95 g/100 g of dietary protein for optimum growth, efficient feed utilization and whole-body protein content. A 17-week feeding trial was carried out to evaluate the effects of dietary L-carnitine level in beluga, Huso huso. A total of fish averaging 1247 ± 15.6 g (mean ± SD) were randomly distributed into 18 fibreglass tanks, and each tank holding 10 fish was then randomly assigned to one of three replicates of six diets with 50, 150, 350, 650, 950 and 1250 mg L-carnitine kg-1 diet. At the end of 17 weeks of feeding trial, average weight gain (WG), feed efficiency (FE), protein efficiency ratio (PER) and condition factor (CF) of fish fed 350 mg kg^-1 diet were significantly (P 〈 0.05) higher than those of fish fed 50, 150, 950 and 1250 mg kg-1 diets. WG, FE, PER and CF of beluga fed 650 mg kg^-1 diet were also significantly higher than those of fish fed 50, 950 and 1250 mg kg^-1 diets. Whole body and muscle protein were significantly improved by the elevation of dietary L-carnitine level up to 350 mg kg^-1. Liver superoxide dismutase and glutathione peroxidase activities of fish fed 350 and 650 mg kg^ -1 diets were significantly higher than those of fish fed 50, 950 and 1250 mg kg^-1 diets. The dietary Lcarnitine level of 350–650 mg kg^-1 diet could improve growth performance, feed utilization, protein-sparing effects of lipid, antioxidant defence system and reproductive success. Polynomial regression of WG suggested that the optimum dietary L-carnitine level was 480 mg kg^-1 diet. Therefore, these results may indicate that the optimum dietary L-carnitine could be higher than 350 but 〈650 mg kg^-1 diet in beluga reared in intensive culture conditions.

Description: Regarding the fish farming in cages, taking into account all nutritional requirements appropriate to the needs of aquaculture is essential in order to minimize damage to the environment and achieve maximum growth. Fish nutritionists should be aware about the analysis of ability to digest and absorb nutrients in the diet to prepare and adjust the diet according to the needs of aquaculture. Food must also have appropriate physical properties for food intake with minimal loss of nutrients in the water. Inadequate resources with low quality or energy consumption within food, reduced the growth performance and increased the excretion of nitrogen in the environment. Food must be designed so that the balance of minerals in food will help maintain osmotic pressure within the body of fish in salty water. Food requirements and efficiency of food conversion ratio (FCR) is variable by changing environmental conditions (dissolved oxygen, temperature, water quality, flow rate, light intensity ,day length). The fish of cages are feeding by floating pellets which have the ability to stand in the water column. The floating pellets allows the fish to have sufficient time and opportunity for finding food. But sinking pellets pass rapidly from the cage and are inaccessible to fish. According to the Caspian sea conditions is better the extruded food equipped with Hygenizer to be used that a portion of it remains on the water surface and part of it moves gently down with an immersion mode in the water column (Softly deposited) for fish consumption. The amount, number and time of feeding are important factors to assess the nutritional activities. In general, fish feed from dry food between 2 to 3 percent of their body weight. Food consumption was also varied due to the quality of the food and fish physiological factors such as age, size, stage of life and stress level. Fish food distribution being fed manually or by means of demand, launcher and automatic feeding. The farm managers should pay attention to the things like water flows in the cage, wind, fish appetite, consolidated flows in the cage during food distribution as well as food storage in dry places with proper ventilation system to prevent the growth of fungi and insects activities to prevent loss of food. Also, adding antioxidants to the 100150 ppm when storing dry foods including the important cases particularly in prevention of fish liver lipoidosis disease is considered.

Description: The present study was conducted to determine ideal diets for the commercial culture of beluga under rearing conditions. The objective of this study was to determine optimum protein levels in adaptation, growth and maintenance diets used in the four study phases. In the first phase 2400 beluga larvae with an average weight of 400-700 mg were stocked at a density of 200 larvae m-2 . Four treatments were used and four replicates run for each treatment. On the basis of results obtained, larvae in Treatment A showed highest growth (P〈0.05). In the second phase, beluga specimens with an initial weight of 4.3 ± 0.14 g were studied for a period of 139 days in a random block design and were fed three different experimental diets at a rate of 2-3 % of their body weight. Three replicates were used for each treatment. Percentage body weight increase (% BWI), FCR, SGR and growth rates were significantly influenced by the protein content of the diets used (P〈0.05). On the basis of Analysis of variance and Tukey Test conducted on results obtained the protein requirement for beluga in the 5-50 g weight class is about 50 %, and with an increase in body weight to about 120 g the protein requirement decreases to 45 %. Therefore diets can be formulated from good quality protein sources 45-50 % crude protein to achieve maximum growth in juvenile hatchery reared beluga. In the third phase 130 day old beluga specimens with an average body weight of 95 ± 1.2 g were reared for a period of 110 days on five experimental diets (three replicates run for each treatment) containing 40-50 % protein and similar levels of fat and energy. In the forth phase 240 day old specimens with an average body weight of 453.3 ± 8.3 g were reared on three experimental diets (ideal diets determined from first phase) (three replicates run for each treatment) for a period of 120 days. Diets were fed four times a day at 1.5 2 % of body weight. It is evident from the comparison of mean values in different treatments studied that different levels of protein produce varying effects on growth rates in beluga specimens. Significant increase in body weight, SGR value and final body weight was observed in beluga specimens that were fed on diets containing high protein from suitable protein sources (P〈0.05). FCR values also improved in diets containing high protein but was not (P〈0.05). On the basis of maximum % BWI, growth and minimum FCR values it is evident that the maximum crude protein requirement in beluga sturgeon in the weight range of 90 550 g that produces good growth and has no adverse effect on body composition is about 45 ± 2 % from a suitable protein source. Although fishes fed diets containing 50 ± 1 % crude protein showed better growth rates as compared to those fed diets containing 45 % protein, no significant differences were observed. It was also evident that protein requirement for beluga sturgeon in the 500-1000 g body weight range is 40 ± 2 g from a suitable protein source. Beluga sturgeons weighing 20.51 ± 0.32 to 1068.23 ± 26.35 g were studied in three study phases for a period of 335 days in fiberglass tanks (500 L) in order to determine the ideal number of feeds. Water flow into the tanks was maintained at 0.15 L sec-1 and fishes were fed 3, 5 and 8 times per day. Three treatments were used in each study phase and three replicates were run for each treatment. On the basis of results obtained from the first phase (mean weight 20.51 ± 0.32 g) increase in number of feeds resulted in higher growth rates, % BWI, SGR and lower FCR values however no significant differences were observed in the three groups under study (P〉0.05). In the second phase (mean weight 77.55 ± 1.18 g) on the basis of the variations in weight in the first and final biometric measurements it was clear that Treatment C (8 times feeding per day) was different from other treatments (P〈0.05). However no significant differences were observed among the treatments studied regarding FCR, SGR etc. (P〉0.05). No significant differences were observed among the treatments in length and weight measurements carried out in the third phase (mean weight 257.61 ± 6.08 g) (P〉0.05). On the basis of SGR, FCR and % BWI values and growth rates observed during the rearing period it can be concluded that increase in number of feeds given per day has no significant effect on the parameters studied. Fish can adapt itself to the feeding times and intervals, however since feeding is carried out manually in Iran, best results for growth are achieved when feeds are given 8 times during the day in the early stages (30-50 g) and 3-5 times, preferably 4 times, for 50-70 to 1000 g weight classes. The effect of stocking density on growth rate, FCR and survival rate was studied in three study phases in order to determine ideal stocking densities for hatchery reared beluga in the 49.44 ± 1.52 to 2158.88 ± 26.82 g weight class. The study was conducted for a period of 270 days in 2000 L fiberglass tanks under similar conditions of rearing. Water exchange was carried out at a rate of 15-20 % per hour. In the first phase two stocking densities (300 and 500 specimens /m 2 ) with a mean weight of 49.44 ± 1.52 g were considered. This phase lasted 65 days. In the second phase, 3 stocking densities (1.6, 2.8 and 4 kg/m 2 ) were considered. The mean weight of fishes was 92.09 ± 1.72 g and this phase lasted 100 days. Four stocking densities (1.5, 2.5, 3.5 and 4.5 kg/m 2 ) were considered in the third phase. This phase lasted 120 days and the mean weight of fish was 918.13 ± 21.87 g. The results obtained indicate adverse effects of increase in stocking density on % BWI, SGR and FCR values. Fishes stocked at higher density in phase one showed body wounds and deformed fins as a result of crowding. Significant differences (P〈0.05) were observed in growth rates recorded for fishes stocked at lower densities (1.6 kg/m 2 ) in phase two as compared to those recorded for fishes stocked at 2.8 and 4 kg/m 2 . In the third phase of rearing growth rates in fishes decreased with an increase in stocking density. Fishes stocked at 1.5 kg/m 2 showed 7.2, 15.6 and 19.8 % higher growth rates as compared to fishes stocked at 2.5, 3.5 and 4.5 kg/m 2 , respectively (P〈0.05). Statistical analysis of results obtained from the present study indicate that increase in stocking density per unit surface area causes a decrease in feeding surface area for each individual fish (considering the bottom feeding behavior in beluga) and thus results in different weight classes, feeding interaction among fishes and ultimately leads to unequal shares in food intake, increases fluctuations in length and weight and lowers the advantages of feeds. On the basis of the results obtained ideal stocking density in the early stages of rearing beluga up to a weight of 50-10 g can be stated as 1.5 to 2 kg/m 2 and 2.5 to 3 kg/m 2 for rearing above 900 g. Growth in A. persicus and beluga from the larval stage up to one-year class was studied under similar conditions of rearing in fiberglass tanks for a period of 411 days. Three replicates were run for each treatment. Fishes were fed granule feeds containing 40 % protein and 13 % fat. The mean weight of A. persicus increased from 16.6 ± 0.51 g to 417.15 ± 26.5 g and that of beluga increased from 41.59 ± 0.83 to 928.47 ± 46.9 g at the end of the rearing period. Moreover despite cannibalism observed in beluga in the larval stage, this species adapted easily to formulated diets and showed suitable survival rates. Results obtained from growth rates (weight and length) and other parameters such as FCR, SGR and % BWI that were calculated from growth rates indicate that beluga exhibits significant growth rates as compared to A. persicus under similar conditions of rearing (55.1 % higher growth rates as compared to those in A. persicus). On the basis of the results obtained from a 29 weeks study period carried out on the commercial culture of beluga with a mean weight of 33.75 ± 0.35 g in fiberglass tanks and earthen ponds. At the end of the study period of 200 days, beluga specimens reared in fiberglass tanks showed an increase in weight of 572 g and a production 6 kg m-2 . The percentage survival, FCR and SGR values recorded for this group were 98.4 %, 2.21 and 1.41, respectively. The weight increase and production for beluga specimens reared in earthen ponds during the same study period were 708 g and 1.5 kg m-2 , respectively. The percentage survival, FCR and SGR recorded for this group were 85.7 %, 1.32 and 1.69, respectively. No significant differences (P〉0.05) were observed in the different parameters recorded in the two groups studied, however SGR and FCR values obtained for beluga specimens reared in earthen ponds were more suitable. Growth rate on the other hand was significantly influenced by the rearing system (P〈0.05). Data obtained indicate that the mean weight of beluga specimens reared through a period of 17 months in fiberglass tanks (2 x 2 x 0.53 m) increased from 0.2 g to 3753 ± 72.2 g. The percentage survival was 90 % and FCR and SGR recorded for this period were 2.02 and 1.01 ± 0.15, respectively. Therefore it can be concluded that beluga can be reared in aquaculture systems under the climatic conditions in Gilan. Water exchange for rearing tanks should be carried out 4-5 times per day and at a rate of 10-12 % per day in earthen tanks. From the economic point of view the net profit obtained from fiberglass tanks is 8000-10000 Rials per kilogram sturgeon meat. Application of aeration, suitable water quality and use of low quality fish in diets in order to lower costs leads to higher productions per unit area and thus results in higher profits.

Description: Iranian Fisheries Science Research Institute

Description: Published

Description: This study was conducted to evaluate the effect of replacing dietary fish rations with canola rations on the growth rate, survival rate and body composition of the Siberian sturgeon (Acipenser baerii Brandt). Five isonitrogenous (45% crude protein) and isocaloric (18.53 MJg-1 ) diets were formulated by replacing 0 (control), 10 (C10), 20 (C20), 30 (C30) and 40% (C40) of fish rations with canola rations. Juvenile fish with an initial weight of 22.80 ± 0.34 g (mean ± SD) with five treatments and three replications were fed for 10 weeks. At the end of the experiment, the growth rate, survival rate and body composition of the fish were measured. The results of this study showed that there was significant differences in the growth indices and body composition of the fish that were fed the different diets (P〈0.05). The lowest growth rate was observed in C40, with significant differences in the growth rate between C40 and the other treatments (P〈0.05). There were no significant differences in the growth rate between C30 and C40 (P〉0.05). The survival rate was 100% in all treatments. There were no significant differences in body protein, lipid and ash contents in the different treatments (P〉0.05), but significant differences were observed in the moisture content of the body of the fish that were fed different diets (P〈0.05). The results of the present study suggest that 30% of fish rations can be replaced by canola rations without any negative effects on the growth rate, survival rate and body composition of the Siberian sturgeon.

Description: Published

Description: Growth experiments were designed and conducted in several phases in order to determine the most suitable starter diet, to determine the effects of different levels of protein and energy and also to determine the effects of different ratios of carbohydrate to fat on growth and body composition in farmed Huso huso from the larval stage up to the marketing stage. Phase one Growth experiments were conducted in a random statistical design to compare growth trends in H. huso larvae (mean weight 105.02 ± 0,02 mg) without being adapted to formulated diets. Experiments were conducted in fibreglass tanks (500 litre capacity) under similar culture conditions. Four replicates were run for each experiment. Larvae were fed four types of formulated diets (Diet A=100 % formulated diet produced in the International sturgeon Research Institute, Diet B=formulated diet imported from Holland, Diet C= formulated diet imported from France, Diet D= a mixture of Diet A + 10% gammarus) 8 times a day to satiation for a period of 49 days. The results obtained were compared with those obtained for the control group that was fed live food (Daphnia and Artemia). Mean water temperature during the experimental period was 18.52 ± 0.48 ?C and mean dissolved oxygen was 7.35 ± 0.18 mg/l. The first signs of food granules were observed in the guts of the larvae after 12 h of the first feeding. All experimental groups were adapted to granulated diets on day 3 to day 5. In the beginning of the experimental period the larvae showed a no normal distribution (P 0.05) in terms of weight and length. However significant differences were observed in the end of the experimental period among the different groups studied in terms of growth, specific growth rate and food efficiency (P 0.05). Growth in group B and D were significantly higher than that in other groups except for the control group (P 0.05). It may thus be concluded that the olfactory organs of larvae took to Diet B (may be due to its composition) and to the diet D (because of its odour, texture and suitable flavour) more readily than other diets. At the end of the experimental period, maximum survival (98%) belonged to the control group. Survival rate in Group B and Group D was 90 % and 86.5%, respectively (P 0.05). Minimum survival belonged to fish fed Diet A (29.7%) and Diet C (45.5%). With regard to the adaptability of larvae to formulated diets, survival rates and growth and development in larvae we may conclude that the effects of different formulated diets on growth in larvae can be conducted on larvae with a mean body weight between 100 to 120 mg. In this weight class the digestive system and olfactory organ are fully developed and play a vital role in searching for food particles.

Description: Iranian Fisheries Science Research Institute

Description: Published

Description: Regarding the fish farming in cages, taking into account all nutritional requirements appropriate to the needs of aquaculture is essential in order to minimize damage to the environment and achieve maximum growth. Fish nutritionists should be aware about the analysis of ability to digest and absorb nutrients in the diet to prepare and adjust the diet according to the needs of aquaculture. Food must also have appropriate physical properties for food intake with minimal loss of nutrients in the water. Inadequate resources with low quality or energy consumption within food, reduced the growth performance and increased the excretion of nitrogen in the environment. Food must be designed so that the balance of minerals in food will help maintain osmotic pressure within the body of fish in salty water. Food requirements and efficiency of food conversion ratio (FCR) is variable by changing environmental conditions (dissolved oxygen, temperature, water quality, flow rate, light intensity ,day length). The fish of cages are feeding by floating pellets which have the ability to stand in the water column. The floating pellets allows the fish to have sufficient time and opportunity for finding food. But sinking pellets pass rapidly from the cage and are inaccessible to fish. According to the Caspian sea conditions is better the extruded food equipped with Hygenizer to be used that a portion of it remains on the water surface and part of it moves gently down with an immersion mode in the water column (Softly deposited) for fish consumption. The amount, number and time of feeding are important factors to assess the nutritional activities. In general, fish feed from dry food between 2 to 3 percent of their body weight. Food consumption was also varied due to the quality of the food and fish physiological factors such as age, size, stage of life and stress level. Fish food distribution being fed manually or by means of demand, launcher and automatic feeding. The farm managers should pay attention to the things like water flows in the cage, wind, fish appetite, consolidated flows in the cage during food distribution as well as food storage in dry places with proper ventilation system to prevent the growth of fungi and insects activities to prevent loss of food. Also, adding antioxidants to the 100150 ppm when storing dry foods including the important cases particularly in prevention of fish liver lipoidosis disease is considered.

Description: Iranian Fisheries Science Research Institute

Description: Published