Effects of Dietary Soybean Oil Replacement by Silkworm,Bombyx mori L., Chrysalis Oil on Growth Performance,Tissue Fatty Acid Composition,and Health Status of Juvenile Jian Carp,Cyprinus carpio var. Jian

Five triplicate groups containing 15 Jian carp (33.51 ± 1.91 g) were fed five isonitrogenous (30%) and isolipidic (8%) diets, with an increase in silkworm chrysalis oil (SCO) to replace soybean oil (SO) at 0 (SO), 25 (SCO25), 50 (SCO50), 75 (SCO75), or 100% (SCO100) levels for 59 d. Results showed that the SCO50 and SCO75 groups presented higher thermal growth coefficients than the SO and SCO100 groups and lower feed conversion ratios than the SCO100 group (P < 0.05). Moreover, the 50% SCO‐supplemented level decreased hepatopancreas lipid content and increased muscle crude protein content (P < 0.05). Meanwhile, α‐linolenic acid, n‐3 polyunsaturated fatty acid (PUFA) content, and n‐3/n‐6 PUFA ratio increased in the hepatopancreas, and intraperitoneal fat and muscle as the replacement of SO increased (P < 0.05). No significant differences of the serum biochemical indices and hepatopancreatic malondialdehyde content were found among groups (P > 0.05), but hepatopancreatic superoxide dismutase activities in the SCO25 and SCO50 groups were significantly higher than those in the other groups (P < 0.05). There was no significant difference in muscularis coat thickness, fold height, and fold width in the mid‐intestine (P>0.05). Overall, up to 50 or 75% replacement of SO by SCO in the diet of Jian carp could improve growth performance without affecting the health status of the fish.     

Effects of total fish oil replacement to vegetable oils at two dietary lipid levels on the growth,body composition,haemato‐immunological and serum biochemical parameters in caspian brown trout (Salmo trutta caspius Kessler, 1877)

This research aimed to evaluate the effects of two dietary fat levels [low fat (LF) (10%), high fat (HF) (20%)] and sources [fish oil (FO), vegetable oil (VO)] on the growth and some physiological parameters of Caspian brown trout fingerlings for 60 days. Tuna oil or blends of canola and soybean oils (85:15) were added to diets to design four feeds namely LFFO, HFFO, LFVO and HFVO according to the fat levels and sources. The fish fed the LFFO diet had lower weight gain than the other fish (P<0.05). The total n‐6 fatty acids increased in fish fed diets with the blends of VO, while the total n‐3 fatty acids decreased in these fish (P<0.05). Serum lysozyme activity was higher in fish fed the HFVO diet than the other fish (P<0.05). Serum glucose, total cholesterol, triglyceride and very low‐density lipoprotein were lower in fish fed LFFO than the other fish (P<0.05). The present study demonstrates that in terms of fish growth, VOs can be used as an alternate source of dietary fat, whereas fish health and nutritional value are improved with the LFFO diet. According to these results, a partial substitution of FO by VO in high‐level fat diets is suggested for long‐term feeding of Caspian brown trout.     

Influence of Dietary Oil Sources on Muscle Composition and Plasma Lipoprotein Concentrations in Nile Tilapia,Oreochromis niloticus

To investigate the impact of different dietary lipid sources on fillet composition and lipid transport, we conducted a feeding trial and evaluated the proximate composition of muscle tissue, fatty acid profiles, total cholesterol (in muscle and plasma), triglycerides, and lipoprotein concentrations in Nile tilapia, Oreochromis niloticus. Five semi‐purified diets, containing different oils (soybean – SO, corn – CO, linseed – LO, fish – FO, and olive – OO), were supplied to tilapia for 160 d. Fish fed with LO and FO diets had a lower percentage of total lipids in muscle compared with the others (P < 0.05). The highest percentage of protein was found in fish fed with FO diet (P < 0.05). The muscle fatty acid profile was influenced differently by diets (P < 0.05). The group supplemented with SO and CO had a higher concentration of 18:2n‐6, whereas the fish fed with LO diet had a higher level of 18:3n‐3 and those that received the FO diet had more 22:6n‐3 in comparison with those supplemented with vegetable oils. Plasma lipid transport was also affected by the diets: the fish fed with FO diet had higher total cholesterol and high‐density lipoprotein and lower very‐low‐density lipoprotein concentrations (P < 0.05).     

The use of tuna industry waste in the practical diets of juvenile Nile tilapia (Oreochromis niloticus,L.): effect on growth performance,nutrient digestibility and oxidative status

A 45‐day feeding trial was conducted to study the effect of replacing dietary fish meal (FM) with a tuna by‐product meal (TBM) on the growth, feed efficiency, carcass composition and stress oxidative status of juvenile Nile tilapia, Oreochromis niloticus L.). Triplicate groups of fish (2.21 ± 0.01 g) were fed on four iso‐nitrogenous and iso‐energetic diets. The control diet (A₀) used FM as the sole source of animal protein. In the other three diets (A₁₀–A₃₀), 33%–100% of FM was substituted by TBM at 10% increments. There were no significant differences (P>0.05) in growth performance among fish fed on diets A₀, A₁₀ and A₂₀. Fish fed these experimental diets (i.e., A₀, A₁₀ and A₂₀) showed significantly (P<0.05) better daily mass gain, specific growth rate and protein efficiency ratio than those fed on diet A₃₀. Feed conversion ratio increased with increasing TBM content, but only the value found in fish fed on diet A₃₀ differed significantly (P<0.05) from the other treatments. The fish accumulated increasing quantities of lipids and decreasing levels of ash in their carcasses with increasing levels of dietary TBM. At the end of the experimental period, a significant increase (P<0.001) in catalase and glutathione S‐transferase activities was seen only in groups fed on diet A₃₀. Similarly, a significant enhancement in glutathione peroxidase and superoxide dismutase activities was observed in groups fed on diets A₂₀ and A₃₀ compared with the other groups. The results show that this product can be included up to 20% in practical Nile tilapia diets without any detrimental effects.     

Effects of Dietary Vitamin C on Blood Chemistry and Nonspecific Immune Response of Juvenile Red Sea Bream,Pagrus major

A trial was conducted to determine the effect of ascorbyl‐2‐monophosphate Na/Ca (AMP‐Na/Ca) on blood chemistry and nonspecific immune response of red sea bream juveniles. Test diets with three levels of AsA (free, 107, and 325 mg/kg diet) were fed to juvenile red sea bream (36.0 ± 1.3 g) two times a day for 3 wk. There were no significant differences in hematocrit, glucose, and blood urea nitrogen. Total cholesterol and triglyceride in plasma of fish fed AsA‐free diet was significantly (P < 0.05) higher than that of fish fed two other diets. There were no significant differences in serum albumin, total bilirubin, and total serum protein. Glutamyl oxaloacetic transaminase in serum of fish fed diets containing 107 and 325 mg of AsA were significantly (P < 0.05) lower than that of fish fed AsA‐free diet. Serum lysozyme activity (LA) of fish fed diets containing 107 and 325 mg of AsA were significantly (P < 0.05) higher than that of fish fed AsA‐free diet. There was no significant difference in mucus LA. The results mentioned above demonstrated that AMP‐Na/Ca is a bioavailable AsA source for red sea bream juveniles. Supplement of more than 107 mg AsA/kg in diets improved blood chemistry and nonspecific immune function of red sea bream juveniles.     

Impact of starvation on digestive enzymes activities and plasma metabolites in Siberian sturgeon (Acipenser baerii,Brandt, 1869)

To increase the current knowledge about the relationship between nutritional status and the digestive capacity of Siberian sturgeon (Acipenser baerii), we addressed the effect of starvation‐refeeding and macronutrient composition on growth parameters and key digestive enzyme activities in A. baerii. Acipenser baerii juveniles were fed four different diets for 3 weeks, then starved for 2 weeks and allowed to refed for 5 weeks with the same diets. Another group of fish were fed 10 weeks with the corresponding diets. Among 10‐week fed fish, high‐protein diets promoted higher body weight values, while the lowest specific growth rate was observed in fish fed a low‐protein, medium‐carbohydrate, high‐lipid diet (p < .05). At the end of the experiment, in fish refed for 5 weeks following a feeding‐starvation cycle and in 10‐week fed animals, the higher levels of blood glucose, triglycerides and cholesterol were found in fish fed low‐protein diets (p < .05). In all treatments, 2 weeks of starvation decreased α‐amylase activity in the intestine (p < .05), while 4 days of refeeding increased lipase (p > .05) and α‐amylase activity in the intestine as well as pepsin in the stomach (p < .05). Our findings suggest that A. baerii maintains a high capacity to digest proteins and lipids after 2 weeks of starvation and that α‐amylase can be used as an indicator of the nutritional status in fish submitted to starvation‐refeeding cycles. Indeed, refeeding with high‐protein and CHO:L ratio diets after starvation could improve the growth rate of A. baerii in culture.     

Effects of the Dietary Fermented Tuna By‐product Meal on Growth,Blood Parameters,Nonspecific Immune Response,and Disease Resistance in Juvenile Olive Flounder,Paralichthys olivaceus

This study evaluated the effects of dietary fermented tuna by‐product meal (FTBM) in juvenile olive flounder, Paralichthys olivaceus. Five diets were formulated to replace fishmeal (FM) with FTBM at 0% (FTBM₀), 12.5% (FTBM_12.5), 25.0% (FTBM₂₅), 37.5% (FTBM_37.5), or 50% (FTBM₅₀). After 8 wk, weight gain, specific growth rate, and feed efficiency of fish fed FTBM₀ and FTBM_12.5 diets were significantly higher than fish fed the other diets (P < 0.05). Also, mean cumulative survival rates (%) of fish fed the FTBM₀ and FTBM_12.5 diets were significantly higher than those fed FTBM₅₀ diet at Day 9 postchallenge with Edwardsiella tarda (P < 0.05). Protein efficiency ratio of fish fed FTBM₀ and FTBM_12.5 diets was significantly higher (P < 0.05) than fish fed diets FTBM_37.5 and FTBM₅₀. Broken‐line regression analysis of weight gain showed an optimal FM replacement level of 10.65% with FTBM. Therefore, the optimal dietary inclusion of FTBM in juvenile olive flounder diets could be greater than 10.65% but less than 12.5% without any adverse physiological effects on fish health.     

Growth,Survival, and Whole‐body Proximate and Fatty Acid Composition of Haddock,Melanogrammus aeglefinus L., Postlarvae Fed a Practical Microparticulate Weaning Diet

Further development of high‐quality feeds for hatchery‐reared haddock in the North Atlantic would benefit from a standard formulation that can be used as a reference for hatcheries and laboratory studies. A practical microparticulate diet (PMD) developed and evaluated with newly metamorphosed juvenile haddock, Melanogrammus aeglefinus L., postlarvae is proposed. Survival of fish fed PMD was just as high (88–89%; P > 0.05) as those fed a high‐quality imported feed (Biokyowa). Alternatively, fish fed PMD had higher (P < 0.05) final fork lengths (39.5 vs. 35.1 mm), wet weights (851.3 vs. 580.2 mg) and weight gains (1637.2 vs. 1115.7%). No differences (P > 0.05) in whole‐body moisture (846–857 g/kg), ash (17–18 g/kg), or protein (101 g/kg) contents were found. Lipid content of fish fed PMD (26 g/kg) was higher (P < 0.05) than those fed Biokyowa (21 g/kg) despite PMD containing 15 g/kg lower dietary lipid, suggesting higher intake and/or lipid retention. The PMD formulation proved to be a highly suitable weaning diet for haddock postlarvae based on high feed acceptance, survival, and fish growth. Given the economic and logistical difficulties associated with importing commercial weaning feeds, this easily produced practical weaning diet has good potential for use by laboratory researchers and farm managers for hatchery‐based nutrition research with haddock postlarvae.     

Dietary Protein Level Affects the Growth Performance of Large Male Genetically Improved Farmed Tilapia,Oreochromis niloticus,Reared in Fertilized Freshwater Cages

An 8‐wk experiment was conducted to evaluate the effects of dietary protein on the growth performance, body composition, and serum biochemical indices of large male genetically improved farmed tilapia (GIFT), Oreochromis niloticus, reared in fertilized freshwater cages. Six semi‐purified diets were formulated, containing 18.05, 22.39, 25.97, 31.62, 35.97, and 39.89% protein (designated as P18, P22, P26, P30, P34, and P38, respectively). Each diet was fed to randomly selected fish (initial mean weight 216.7 g) in four cages. At the end of the experiment, the final body weights varied significantly (P < 0.05), ranging from 520 to 580 g. Fish receiving the P30 diet had the highest final weight value (580.5 ± 5.4 g). Weight gains of fish fed the P26 and P30 diets were significantly higher (P < 0.05) than those fed the P18 and P38 diets. The apparent feed efficiency of fish fed the P18 diet was significantly lower (P < 0.05) than that of fish in the other groups except the P22 group (P > 0.05). The apparent protein efficiency ratio decreased gradually with increasing dietary protein. Whole‐body moisture and ash showed no significant difference (P > 0.05), but protein and fat content were significantly affected by dietary protein level (P < 0.05). No significant differences were found for serum total protein, triglyceride, total cholesterol, glutamic‐oxaloacetic transaminase, and glutamic‐pyruvic transaminase levels among different diets (P > 0.05); only serum glucose level was affected by dietary protein levels (P < 0.05). Second‐order polynomial regression of weight gain suggested 29.3% dietary protein is adequate content for maximum growth of large male GIFT, O. niloticus.     

Effects of Dietary Inclusion of Chlorella vulgaris on Growth,Blood Biochemical Parameters,and Antioxidant Enzyme Activity in Olive Flounder,Paralichthys olivaceus

This study was carried out to investigate the effects of dietary inclusion of defatted Chlorella on growth performance, body composition, blood biochemistry, and antioxidant enzyme activity in olive flounder. Four isonitrogenous (51% crude protein) diets were formulated to contain 0 (control), 5, 10, or 15% Chlorella meal (CM) (designated as Con, CM5, CM10, and CM15, respectively) and fed to triplicate groups of fish (104.4 g) to apparent satiation twice daily for 8 wk. At the end of the feeding trial, significant enhancement (P < 0.05) in growth performance was obtained at over 10% CM compared to fish fed the control diet. No significant changes in dorsal muscle and liver proximate composition were found following CM administration. The groups fed CM‐containing diets revealed significantly lower plasma cholesterol concentration than those fed the control diet. Dietary CM affected antioxidant enzyme activity; significantly higher plasma catalase activity was found in fish fed ≥10% CM and total antioxidant capacity increased in CM5 and CM10 groups compared to the control. However, plasma glutathione peroxidase and superoxide dismutase activities were not significantly influenced by dietary CM. Also, significant enhancement in 1,1‐diphenyl‐2‐picryl‐hydrazyl radical scavenging activity was found in dorsal muscle of fish fed CM15 diet compared to the control. The findings in this study showed that dietary inclusion of 10–15% CM can enhance growth performance and affect antioxidant enzyme activity and lipid metabolism in olive flounder.     

Growth,enzymatic glutathione peroxidase activity and biochemical status of juvenile barramundi (Lates calcarifer) fed dietary fermented lupin meal supplemented with organic selenium

To investigate the effects of high level of lupin meal (LM) supplemented with organic selenium (OS) on the growth and blood biochemistry of barramundi (Lates calcarifer), four isocaloric and isonitrogenous diets were prepared, containing either non‐fermented or fermented LM, and either supplemented with 2 mg OS/kg (LM, LM_OS, FLM and FLM_OS), or not. A fishmeal (FM)‐based diet formulated for juvenile barramundi was used as a control diet. Fish (initial mean weight of 5.88 g) were triplicated and fed the test diets for 75 days. The findings demonstrated that growth performance of fish fed with the FLM and FLM_OS diets were similar to fish fed with the FM diet (p > .05). The antioxidant glutathione peroxidase (GPx) activity, and haemoglobin (Hb) of fish fed with the FLM_OS diet were significantly higher than that of FM‐fed fish (p < .05). Plasma alanine aminotransferase (ALT) activity was significantly increased in fish fed with non‐fermented diets (LM and LM_OS) than in those fed with fermented LM diets (FLM and FLM_OS) (p < .05). However, there were no significant differences in ALT activity among LM_OS, FLM, FLM_OS and FM diets. There was an interaction between the LM and OS on plasma CK activity; the CK of fish fed with diets supplemented with OS was higher in non‐fermented LM diets but lower in fermented LM diets (p < .05). This study suggests that fermented LM have an obvious potential to substantially replace 75% FM protein in the diets of barramundi.     

Effect and interaction of rainbow trout strain (Oncorhynchus mykiss) and diet type on growth and nutrient retention

Eight strains of rainbow trout were introgressed to develop a single strain (H‐ARS) that was selected for faster growth when fed a fishmeal‐free, plant‐based diet (Selection Diet). For four generations, families from these crosses were fed the Selection Diet and selected for increased weight gain. Growth and nutrient retention were compared among H‐ARS and two parental strains, the House Creek (HSC) and Fish Lake (FL) fed either a fish meal or Selection diet for 12 weeks. There was a significant effect of strain (P < 0.01), but not diet on weight gain, and a significant interaction of strain by diet (P < 0.05). The H‐ARS trout gained more weight averaged across diet (991% of initial wt.) than the HC (924%) or FL trout (483%). The FL trout fed the fish meal diet gained more weight than FL trout fed the selection diet (510% vs 456%). Conversely, H‐ARS trout fed the plant‐based diet gained more weight than those fed the fish meal diet (1009% vs 974%). HSC trout had similar weight gain fed either diet (922% vs 926%). A significant effect of strain on protein retention (P < 0.01) was observed, along with a significant strain by diet interaction (P < 0.02). The results demonstrate that rainbow trout can be selectively improved to grow on a plant‐based diet.     

Assessing the Effects of Dietary Inclusion of Hydrolyzed Soy Protein on the Growth,Nutrient Retention,Body Composition,and Serum Hormone of Juvenile Starry Flounder,Platichthys stellatus

Enzymatic hydrolysis of soy protein has the potential to be an excellent protein source in marine fish feeds. Here we assessed the effects of different inclusion levels of hydrolyzed soy protein (HSP) on growth performance, nutrient retention, body composition, and serum hormone levels in juvenile starry flounder to define HSP utilization. Five isoenergetic and isoprotein diets were formulated with 0 (control), 10, 20, 30, and 40% HSP (SP10–40) to replace 0, 25, 50, 75, and 100% soy protein concentrate (SPC), respectively. At the end of the feeding trial, fish fed diets SP20 and SP30 had significantly increased weight gain, percent weight gain, and feed efficiency (FE) compared with fish fed the control diet (P < 0.05). Diets SP20 and SP30 supported significantly higher levels of protein retention, and diet SP20 significantly increased energy retention (P < 0.05) in the fish offered these diets. In terms of nutritional composition of whole fish, feeding diets SP20 and SP30 increased crude protein content (P < 0.05) and diets SP10, SP20, and SP30 increased ash content (P < 0.05). Fish fed diets SP20 and SP30 had higher serum insulin‐like growth factor 1 (IGF‐1) level than that of the control treatment (P < 0.05). When SPC was included at 40% of the diet, 20–30% HSP (43% soluble nitrogen) is recommended to replace 50–75% SPC for maximal growth performance and FE of starry flounder.     

Effects of dietary proline on swim bladder collagen synthesis and its possible regulation by the TGF‐β/Smad pathway in spotted drum,Nibea diacanthus

Swim bladder is an ideal source of collagen production in fish for improved human health. Proline (Pro) is the main proteinogenic amino acid needed for collagen production. However, the effects of Pro supplementation on the swim bladder collagen synthesis have rarely been evaluated in fish. We determined the effects of dietary Pro supplementation on swim bladder collagen synthesis and its possible signalling pathway in spotted drum, Nibea diacanthus. A total of 450 N. diacanthus (100 ± 3.05 g) were randomly assigned into six treatments and fed with diets supplemented with different levels of Pro (0, 2.5, 5, 7.5, 10 and 12.5 g/kg of dry diet, hereafter P0, P1, P2, P3, P4 and P5, respectively) for 8 weeks. At the end, we evaluated collagen synthesis in swim bladder and the expression of genes related to TGF‐β/Smad pathway in the fish. Dietary Pro levels increased significantly the contents of crude protein, total collagen (TC) and the levels of some amino acids in swim bladder than the control diet (p < .05). The optimum amount of dietary Pro inclusion in diets for swim bladder collagen synthesis in N. diacanthus was 7.6 and 7.5 g/kg based on crude protein and TC in swim bladder, respectively. Dietary Pro levels increased significantly the proline 4‐hydroxylase (P4H) content in fish serum, swim bladder, muscle and liver tissues than control (p < .05). The relative expression of collagen type I alpha 1 (COL1A1), alpha 2 (COL1A2) and mothers against decapentaplegic homolog 2 (Smad2) genes in liver and swim bladder initially increased significantly as the concentration of Pro and later decreased (p < .05). Similarly, the relative expression of transforming growth factor beta (TGF‐β), P4Ha2 and P4Ha3 genes in the swim bladder increased significantly as dietary Pro levels increased (p < .05). Using K‐means clustering analysis, dietary proline partly promoted collagen accumulation in swim bladder through upregulation of Smad2 and TGF‐βRT genes. Taken together, Pro affected the collagen metabolism in swim bladder, probably by regulating the TGF‐β/Smad pathway, most likely via transient overexpression of Smad2 gene.     

Effects of phospholipid addition to diets with different inclusion levels of fish oil on growth and fatty acid body composition of juvenile swimming crab Portunus trituberculatus

Six experimental diets were designed with two phospholipid (PL; 0% and 1.5%) and three fish oil levels (0%, 1% and 3%) to evaluate the effects of dietary fish oil and PL levels on growth, survival and fatty acid composition of juvenile swimming crab, Portunus trituberculatus. Diets were iso‐energetic and iso‐nitrogenous and each diet was fed to triplicate groups (initially weight, 24.88 ± 0.04 g per crab) for 59 days. Weight gain (WG) and specific growth rate (SGR) increased with dietary PL addition to 0% fish oil‐supplemented diets (P < 0.05). On the other hand, WG and SGR decreased with dietary PL addition to 3% fish oil diets (P < 0.05). Crabs fed PL supplemented diets had higher haemolymph low‐density lipoprotein cholesterol concentrations and muscle crude lipid levels (P < 0.05) than crabs fed a none PL supplemented diet. The percentage of highly unsaturated fatty acids (HUFA; % total FA) in both polar and neutral lipids fractions of muscle tissue only increased in case of PL addition to 0% and 1% fish oil‐supplemented diets (P < 0.05). HUFA levels in the neutral lipids fraction of the hepatopancreas increased by dietary PL addition at each dietary fish oil level (P < 0.05). In this study, both dietary fish oil and PL addition contributed to a high n‐3/n‐6 ratio in muscle and hepatopancreas of P. trituberculatus. In conclusion, PL addition is only meaningful with fish oil‐deficient diets, in which case it enhanced lipid transport and HUFA absorption efficiency, hence improving the nutritional value of the diet.     

Dietary supplement of Enterococcus faecalis on digestive enzyme activities,short‐chain fatty acid production,immune system response and disease resistance of Javanese carp (Puntius gonionotus,Bleeker 1850)

This study investigated the effects of Enterococcus faecalis on digestive enzyme activities and short‐chain fatty acid production in fish intestine, resistance against Aeromonas hydrophila and humoral immunity response by 3 experiments on Javanes carp (Puntius gonionotus). The experiment 1 revealed that diet supplemented with E. faecalis significantly (P < 0.05) increased protease and lipase activities compared to control fed fish. Moreover, E. faecalis supplementation significantly enhanced the production of propionic and butyric acid in the intestine, while no significant difference (P > 0.05) in acetic acid production was observed. In the challenge study (experiment 2), fish were injected (intraperitoneal) with 10⁷ A. hydrophila per ml and survival was significantly improved when fish were fed diet supplemented with E. faecalis compared to control fish. In experiment 3, dietary E. faecalis affected immune system response as fish fed the probiont and exposed to 10⁶ A. hydrophila per ml displayed significantly elevated antibody levels compared to control fed fish. Fish fed diet supplemented with E. faecalis but not exposed to the pathogen revealed significantly higher antibody level than control fish (P < 0.05). Therefore, E. faecalis can be used as a probiotic in Javanese carp farming.     

Effect of feeding frequency on growth,feed utilization,body composition and waste output of juvenile golden pompano (Trachinotus ovatus) reared in net pens

A 6‐week feeding trial was conducted to examine the effect of feeding frequency on growth, feed utilization efficiency, body composition and waste output of juvenile golden pompano Trachinotus ovatus reared in net pens. Fish (10.3 ± 0.5 g) were either fed a formulated diet containing 48.4% crude protein and 5.7% crude lipid at 0.5, 1, 2, 3 or 4 meals per day or fed a raw fish feed at two meals per day as a control. The weight gain (WG) increased with increasing feeding frequency from 0.5 to 3 meals per day (P < 0.05), but did not significantly change with the further increase in feeding frequency from 3 to 4 meals per day (P > 0.05). The feed intake (FI) was lower in fish fed at 0.5 or 1 meal per day than in fish fed at 2, 3 or 4 meals per day (P < 0.05). No significant differences were found in the feed conversion ratio (FCR), nitrogen retention efficiency (NRE), condition factor (CF), nitrogen waste output (NWO) and phosphorus waste output (PWO) between fish fed at 1, 2, 3 or 4 meals per day (P > 0.05), whereas no significant difference was found in the phosphorus retention efficiency (PRE) among the feeding treatments (P > 0.05). The body lipid content increased, whereas the contents of moisture and ash decreased, with the increase in feeding frequency (P < 0.05). At the same feeding frequency, fish fed the formulated diet exhibited lower FI, FCR, HSI, body moisture content, NWO and PWO, but higher NRE, PRE, body lipid content and body phosphorus content than those of fish fed the raw fish feed (P < 0.05). These results suggest that the formulated diet can satisfy nutrient requirements of juvenile golden pompano reared in net pens, and the suitable feeding frequency is 3 meals per day.     

Surviving the effects of barotrauma: assessing treatment options and a ‘natural’ remedy to enhance the release survival of line caught pink snapper (Pagrus auratus)

A new technique to ameliorate the effects of barotrauma was tested based on observations of pink snapper, Pagrus auratus (Forster), inadvertently piercing their everted stomach with their teeth and releasing trapped swim bladder gases. This technique was termed buccal venting and involved piercing the everted stomach protruding into the buccal cavity or out of the mouth with a 16‐gauge hypodermic needle (a practice previously not encouraged). Short‐term (~3 days) survival of buccal‐vented fish was not significantly different from laterally vented fish nor untreated controls. Both buccal and lateral venting techniques were shown to cause no harm and allowed fish to return to depth. The short‐term (1–3 days) post‐release survival of line caught snapper was 88% with no significant difference in survival across three depth ranges tested (37–50, 51–100 and 101–180 m). Survival of sublegal pink snapper (<35 cm TL) was not significantly different (P > 0.05) from that of legal‐sized fish (≥35 cm TL). Healing of the swim bladder was observed in 27% of pink snapper dissected after ≤3 days in captivity, and healing of stomachs was observed in 64% of pink snapper that had been buccal vented. Relatively high post‐release survival rates of line caught pink snapper may offer some protection for snapper stocks where high fishing pressure and legal size restrictions result in the majority of the catch having to be released.     

Effect of replacing dietary fish oil with soybean oil on growth performance,fatty acid composition and haematological parameters of juvenile meagre,Argyrosomus regius

A nutrition trial with meagre, Argyrosomus regius was assessed to determine the effect of dietary replacement of fish oil (FO) by soybean oil (SO) on the growth, feed utilization, body composition, fatty acid composition and basic haematological parameters. Six isonitrogenous (47% crude protein) and isoenergetic (gross energy 22 kJ/g) experimental diets were formulated by replacing 0 (FO), 20 (S20), 40 (S40), 60 (S60), 80 (S80) and 100 (S100) % of the FO with SO. Fish were fed three times daily to near satiation for 14 weeks. The specific growth rate (SGR) of fish fed S100 diet was significantly lower than the other treatments, except SO80 diet. The fish fed SO100 diet displayed significantly higher feed conversion ratio than that of other diets (P < 0.05). It was observed that fish fed the SO100 and SO80 diets displayed haemoglobin (HGB) levels significantly lower (P < 0.05) than fish fed the SO20 diet. Packed cell volume (PCV) of fish fed SO20 diet was significantly higher compared to SO100. The white blood cell (WBC) and red blood cell (RBC) remained unaffected by dietary treatment. The docosahexaenoic acid (22:6n‐3, DHA) and eicosapentaenoic acid (20:5n‐3, EPA) levels of meagre were significantly reduced by the substituting of dietary SO by FO at the end of the feeding period. The level of linoleic acid (18:2n‐6, LA) and linolenic acid (18:3n‐3, LNA) significantly raised in fish fed with SO diets (P < 0.05). The results of this study showed that SO could be replaced FO up to 80% in meagre diet without negative effect on growth performance and basic haematological parameters. Furthermore, the maximum level of FO replacement with SO determined by second order polynomial regression analysis, was 30.1% on the basis of maximum SGR.