Peptones in Silage from Tilapia (Oreochromis niloticus) and Cobia (Rachycentron canadum) Waste as a Culture Medium for Bioprocesses

This study investigated the efficacy of the aqueous fraction obtained after fractionating silage of tilapia (Oreochromis niloticus) and cobia (Rachycentron canadum) in supporting the growth of Escherichia coli and Staphylococcus aureus. The silages were prepared using combinations of citric, formic, and propionic acids. The aqueous fractions, used as test peptones, contained lower levels of total protein. The concentrations of 18 amino acids in all the samples were observed to be lower than those in the commercial peptone. Glutamic acid, lysine, glycine, and aspartic acid were present in higher concentrations than other amino acids, for both types of silage. Biomass production from E. coli culture ranged from 38.4 to 65.9 mg 100 mL^?1 for all the tested treatments, while that for S. aureus was from 26.3 to 53.7 mg 100 mL^?1. This indicated that products from fish silage were effective for bacterial growth in terms of biomass, by providing the main sources of nitrogen and carbon to facilitate their growth. The tested silages yielded similar efficiency to the commercial peptone. The findings revealed that it is feasible for the fish processing industry to incorporate freeze-dried by-products obtained after fractioning waste silage from the processing of tilapia and cobia.     

Comparative analysis of stomach contents of cultured and wild cod, Gadus morhua L.

In a cod enhancement project in a small fjord in western Norway, two groups of reared cod, Gadus morhua L., were released with 6 months’difference in time. After the last release a 3-week fishing survey was conducted. Stomachs from wild and recaptured reared cod of similar size were sampled and analysed. The last released cod had learned to catch the same prey types and in the same relative proportions as the wild cod the second week after release, but mean weight of stomach contents and mean numbers of prey items per stomach were smaller, and a larger proportion of the newly released fish had empty stomachs. Three weeks after release the proportion of empty stomachs was similar to that of wild cod and the first released reared cod, but the food intake was still smaller. The first released group of reared cod, which had spent 6 months in the fjord, seemed to feed as efficiently on wild prey as did wild cod.     

The Effect of K-Lactate Salt and Liquid Smoke on Bacterial Growth in a Model System

The effects of a commercial lactate salt formulation—containing potassium lactate (KL) and potassium acetate (KA)—and liquid smoke (LS) on the growth of selected lactic acid bacteria (LAB; Carnobacterium maltaromaticum, Carnobacterium inhibens, Lactococcus lactis, Lactobacillus curvatus, and Enterococcus faecalis), fish spoilage bacteria (Photobacterium phosphoreum, Pseudomonas putida, and Vibrio vulnificus), and Listeria innocua, were examined in a tryptic soy broth model system at 20ºC based on BioScreen data. The most pronounced inhibition effect on growth of bacteria was seen in the presence of 6% KL + 0.4% KA, used either combined with LS or alone. Only a minor inhibition effect on growth was found in the presence of LS alone. The only exception was Lactobacillus curvatus, which grew quite well in the presence of LS compared to control medium. The growth of Vibrio vulnificus was prevented in 6% KL + 0.4% KA, and significantly inhibited in the presence of 3% KL + 0.2% KA. When V. vulnificus was grown in NaCl, KA, and KL + KA, it was observed that KL + KA had a better inhibition effect than sodium salt within the same concentration range.     

Responses of Atlantic cod <Emphasis Type="Italic">Gadus morhua</Emphasis> head kidney leukocytes to phytase produced by gastrointestinal-derived bacteria

This study identified phytase-producing bacteria that were previously isolated from the gastrointestinal tract of Atlantic cod, Gadus morhua and determined its effect on head kidney leukocytes. Out of the 216 bacterial strains tested, the two phytase producers were identified as Pseudomonas sp. and Psychrobacter sp. based on their 16S rDNA sequence. Crude phytase from these two bacterial strains was produced employing the shake flask method. Even though the total protein of the crude phytase was not significantly different for the two bacteria, the phytase activity of the crude enzyme produced by Pseudomonas sp. (97.1 ± 16.7 U) was significantly higher than that of the enzyme from Psychrobacter sp. (75.9 ± 2.4 U). When cod head kidney leukocytes were incubated with the crude phytase (50 μg ml⁻¹), it resulted in enhanced cell proliferation, higher myeloperoxidase, and acid phosphatase activities. Extracellular responses—respiratory burst activity and hydrogen peroxide production were not enhanced by the crude enzyme. As a consequence, the growth of two pathogenic bacteria Aeromonas salmonicida and Vibrio anguillarum was not suppressed by the supernatants obtained from head kidney leukocytes incubated with the crude bacterial phytase. Thus, the enzyme from phytase-producing intestinal bacteria of Atlantic cod can stimulate intracellular head kidney leukocyte activities but not the production of extracellular substances that are involved in antibacterial response. These have implications on the potential use of bacterial phytase as feed supplement to boost cellular immune response of the fish and could be employed as a health management strategy in culture systems.     

Basal H2-receptor stimulated and pH-dependent acid secretion from an isolated stomach mucosa preparation of the cod,Gadus morhua,studied using a modified pH-static titration method

Gastric acid secretion from isolated cod stomach mucosa was measured using a pH-static titration method. A basal acid secretion rate (BASR) of 6.0±0.6 nEqH⁺min^–1cm^–1 was measured when using 0.9% NaCl as luminal solution. There was a dose-dependent increase in response to histamine between 0.12 and 0.20 M (EC₅₀=0.15 M), above which gastric acid secretion plateaued at 13.5±1.8 nEqH⁺min^–1cm^–1. Ranitidine, a H₂-receptor antagonist, completely blocked the stimulatory effect of histamine and reduced the BASR. The H₁-receptor antagonist, clemastine, did not inhibit the response to histamine. Acid secretion rates decreased significantly when the pH of the luminal side of the mucosa was lowered from pH 5.75 to pH 4.50, indicating that a negative feedback mechanism was operating. Histological staining showed that oxynticopeptic cells were uniformly distributed throughout the cardiac stomach.It is concluded that the acid secretion in the isolated stomach mucosa of cod can be measuredin vitro with a pH-static titration method. The method was used to demonstrate that the BASR is downregulated by a decrease in pH. Furthermore, we conclude that the histamine receptor in the cod stomach mucosa resembles the mammalian H₂-receptor and that histamine is secreted under basal conditions.     

Enzymes from the gut bacteria of Atlantic cod,Gadus morhua and their influence on intestinal enzyme activity

Gut‐associated bacteria of fish are known to produce enzymes which aid in digestion. The presence and activities of these bacteria in cold‐water fishes like Atlantic cod are less known. Therefore, we have characterized the activities of extracellular enzymes of GP21 (Pseudomonas sp.) and GP12 (Psychrobacter sp.), two bacteria isolated from the gastrointestinal tract of Atlantic cod. Additionally, we examined if these bacteria when delivered through feeds could influence the activity of selected intestinal enzymes. GP21 was able to produce amylase, chitinase, cellulase and protease, whereas GP12 could produce only chitinase and protease. These enzymes were produced extracellularly and they were found to be catalytically active at acidic conditions (pH 2–5) and at temperatures ranging from 15 to 30 °C. Orally delivered bacteria could possibly influence the activity of intestinal enzymes after 40 days, rather than after 20 days of feeding. Thus GP21 and GP12, the potential probiotic organisms, could support digestion in Atlantic cod.     

Use of Hydrolysates from Silver Carp (Hypophthalmichthys molitrix) Head as Peptone for Vibrio anguillarum and Optimization Using Response Surface Method (RSM)

The objective of this study was to produce fish peptone (FP) from silver carp (Hypophthalmichthys molitrix) heads by Alcalase® hydrolysis in order to use for growing Vibrio anguillarum instead of the standard peptones applied in the commercial media. An optimization of the FP to be used as culture media was also carried out using the response surface method (RSM). According to the results, the degree of hydrolysis and protein percentage after 24 h was 37.68 mg/mL and 20.74%, respectively. The adjustment of the quadratic model with the experimental data was satisfactory. The analysis of variance showed a high coefficient of determination value (0.930). The results of fish protein hydrolysates also showed that fish by-products modified by enzymatic procedures can be used as low cost nitrogen sources for bacterial growth.     

Growth and lipid composition of Atlantic cod (Gadus morhua) larvae in response to differently enriched Artemia franciscana

Considerable progress has been achieved in the intensive culture of Atlantic cod (Gadus morhua). However, there is little information concerning optimum live-feed enrichments for cod larvae, since many of the techniques used during the larviculture have been borrowed from other fish species and adapted for the production of Atlantic cod. The present study compared four different protocols for the enrichment of Artemia to be used as live feed for cod larvae. The protocols tested were: (1) AlgaMac 2000, (2) AquaGrow Advantage, (3) Pavlova sp. + AlgaMac 2000, and (4) DC DHA Selco + AlgaMac 2000. Larvae were fed differently enriched Artemia between 37 and 59 days post hatch. At the end of the experiment, larvae from treatment 1 [specific growth rate (SGR) = 10.4 ± 0.4% day⁻¹] grew faster than larvae from treatments 3 (SGR = 6.9 ± 0.2% day⁻¹) and 4 (SGR = 4.9 ± 0.4% day⁻¹, P < 0.0001). However, treatments 3 and 4 resulted in better larval survival at the end of the experimental period, estimated to be 3 on a scale from 1 to 5, whereas the survival estimates for the two other groups were 2. The treatments affected the fatty-acid composition of Artemia and of cod larvae. Larvae from treatment 1 had a higher percentage of AA (20:4ω6, P < 0.0001) and ω6DPA (22:5ω6, P < 0.0001) than the other larvae. Levels of DHA (22:6ω3) were similar in larvae from treatments 1 and 4, and higher than in the other larvae (P < 0.0001). Our results suggest that Artemia containing a DHA/EPA/AA ratio of 7/2/1 result in good larval performance. Joseph A. Brown—Deceased September 2005.     

A synthesis of large-scale patterns in the planktonic prey of larval and juvenile cod (Gadus morhua)

Data from 40 published studies of the diet composition of larval and juvenile cod (Gadus morhua) from around the northern North Atlantic were summarized to assess generic patterns in ontogenetic and regional variability in the key prey. The results showed that larvae at the northern edge of the latitudinal range of cod depend primarily on development stages of the copepod Calanus finmarchicus, whilst those at the southern edge depend on Para‐ and Pseudocalanus species. Juvenile cod preyed on a wider range of taxa than larvae, but euphausiids were the main target prey. Analysis of regional variations in the relative abundances of C. finmarchicus and Para/Pseudocalanus spp. in the plankton, as estimated by the continuous plankton recorder (CPR) surveys, showed a similar geographical pattern to the larval cod stomach contents. Comparison of CPR data from the 1960s and 70s with data from the 1990s showed that the boundary between C. finmarchicus and Para/Pseudocalanus spp. dominance has shifted northwards on both sides of the Atlantic, whilst the abundance of euphausiids in the southern cod stock regions has declined. The results are discussed in relation to regional differences in the response of cod stocks to climate variability.     

Application of prospective probionts at early stages of Atlantic cod (Gadus morhua L.) rearing

This work aimed at validating the use of two prospective probionts (Arthrobacter sp. and Enterococcus sp.) at early stages of cod (Gadus morhua L.) rearing. Ova at late post‐fertilized stage and larvae during their first 4 weeks of life were bathed with both probionts, isolated previously from the cod‐rearing environment. This treatment was compared with groups fed rotifers supplemented with a commercial probiotic (Remus^®) and those untreated. Microbiological analyses (total viable counts, presumptive Vibrio and lactic acid bacteria) were performed in rearing systems and larval survival, growth and development were assessed. Larval development was evaluated by proteolytic activity of larval lysates and immunological analysis of important proteins: apolipoprotein A‐I, haemoglobin, C‐reactive protein, C3 and cod serum proteins. Bacterial bathing led to a significantly higher larval weight, length and culturable microbial load in larval gastrointestinal (GI) tract when compared with the control and Remus groups. Development occurred earlier in bathed larvae. However, their survival was negatively affected compared with the control group, but was significantly higher than for the Remus group. The non‐pathogenicity of both probionts was demonstrated by intraperitoneal injection of 13 g cod juveniles. The results suggest that Arthrobacter and Enterococcus probionts affected the larval GI microbiota and contributed to growth, development and digestion, either directly or indirectly.     

Carnobacterium maltaromaticum vs. Vibrio (Listonella) anguillarum in the midgut of Atlantic cod (Gadus morhua L.): an ex vivo study

The present investigation addresses whether the midgut (MG) of Atlantic cod (Gadus morhua L.) is an infection route for Vibrio (Listonella) anguillarum serotype 02 β and if Carnobacterium maltaromaticum, a probiotic bacterium, can out‐compete the pathogen and modulate the autochthonous MG microbiota. This was investigated by using an ex vivo method the intestinal sac, utilized previously in studies on Atlantic cod and Atlantic salmon (Salmo salar L.). Exposure of the MG to V. (L.) anguillarum did not reveal any cell damage indicating that the MG does not appear to be an infection route for V. (L.) anguillarum in healthy Atlantic cod. This finding together with previous observations on Atlantic cod and Atlantic salmon indicate that intestine as an infection route might vary between these two species. When the MG was exposed to C. maltaromaticum, no cell damage or cellular disruptions were observed. As budding from the apices of microvilli was observed in all treatments exposed to bacteria, we suggest that budding might be involved in the primary barrier against bacterial infection. However, to clarify this hypothesis, further studies are needed. Exposure of the MG to the probiotics and pathogenic bacteria indicated that C. maltaromaticum, to some extent, is able to out‐compete V. (L.) anguillarum but the topic merits further investigation. Analysis of the MG microbiota after sterile saline solution and bacterial exposure indicates that bacteria related to Staphylococcus sciuri belong to the autochthonous gut microbiota in Atlantic cod.     

Desalted Cod Spoilage Flora Inhibition by Citric Acid and Potassium Sorbate Combination

ABSTRACT

Desalted cod spoilage isolates were tested in culture broth for growth inhibition by citric acid and potassium sorbate. Preservative effect was also evaluated in refrigeratedcod juice and desalted cod spiked with Shewanella putrefaciens and Pseudomonas fluorescens orputida. Combination of 0.15% citric acid and 0.1% potassium sorbate inhibited growth of approximately 60% of isolates, including the former two strains. Total inhibition was observed for S. putrefaciens and partial inhibition was noticed for P. fluorescens or putida, in both treated juice and desalted cod. Preservatives delayed growth of halotolerant bacteria in cod. Citric acid plus potassium sorbate addition lowered the pH to extend desalted cod shelf life.     

Feeding Levels of the Southern Brown Shrimp Penaeus subtilis in Response to Food Dispersal

The development of efficient feed management strategies in shrimp farming involves the investigation of aspects related to time of feed distribution, feeding rates, feeding frequency, and feed dispersal methods. This work examined the feeding levels of Penaeus subtilis in response to food dispersal method under semi-intensive culture conditions. The study consisted of two treatments: 1) a uniform feed dispersal over the culture area, and 2) concentration of feed in 0.2-m² circular feeding trays. For each, three 105-m² rectangular enclosures were installed in a single shrimp grow-out pond and stocked with P. subtilis at a density of 14.29 postlarvae/m². Shrimp were fed daily at 0600, 0930 and 1430 h and sampled 30 min after feed distribution at 12-d intervals. After collection, shrimp weight was determined, their stomachs dissected and weighed. A total of 2,160 stomachs of P. subtilis were collected during a 89-d rearing cycle. Relative occurrence of artificial versus natural food in stomach contents was determined by stable carbon isotope mass spectrometry. Density of polychaetes in the substrate was monitored at each sampling period. After harvest, sediment samples were collected for physical and chemical analyses. In general, differences in shrimp growth between feeding methods were not significant. Final shrimp survival rates were between 69.0 ± 6.9% and 71.9 ± 3.7%. Stomach content weight of P. subtilis was significantly higher when feed was broadcast than for feed concentration. Average stomach content weight remained constant throughout the rearing cycle, although progressive increases in feed Occurrence were detected in P. subtilis diet. No periodicity in food intake along sampling periods could be related to increases in shrimp carapace length. Food intake was significantly lower at 0600 h than at 1430 h and at 0930 h, respectively. In both treatments, over half of the food contained in the stomach contents of shrimp was derived from artificial food. Sediment chemical analysis indicated statistically lower levels of sodium in the pond bottom of concentrated treatment. However, no short-term detrimental effects were detected on sediment chemical quality. Results indicated that feed broadcasting resulted in a greater access and a higher consumption of food among the cultured shrimp population, a lower number of empty stomachs, and a greater occurrence of artificial food in P. subtilis stomach contents.     

Yersiniosis in Atlantic cod,Gadus morhua (L.), characterization of the infective strain and host reactions

A disease outbreak in farmed Atlantic cod caused by Yersinia ruckeri is reported. Mortality started following vaccination of cod reared in two tanks (A and B). The accumulated mortality reached 1.9% in A and 4.8% in B in the following 30 days when treatment with oxytetracycline was applied. Biochemical and molecular analysis of Y. ruckeri isolates from the cod and other fish species from fresh and marine waters in Iceland revealed a high salinity‐tolerant subgroup of Y. ruckeri serotype O1. Infected fish showed clinical signs comparable with those of Y. ruckeri ‐infected salmonids, with the exception of granuloma formations in infected cod tissues, which is a known response of cod to bacterial infections. Immunohistological examination showed Y. ruckeri antigens in the core of granulomas and the involvement of immune parameters that indicates a strong association between complement and lysozyme killing of bacteria. Experimental infection of cod with a cod isolate induced disease, and the calculated LD₅₀ was 1.7 × 10⁴ CFU per fish. The results suggest that yersiniosis can be spread between populations of freshwater and marine fish. Treatment of infected cod with antibiotic did not eliminate the infection, which can be explained by the immune response of cod producing prolonged granulomatous infection.     

A multivariate approach to optimization of macronutrient composition in weaning diets for cod (Gadus morhua)

Atlantic cod, initial weight 0.26 g, were fed diets varying in added protein from 530 to 830 g kg^?1, lipid from 50 to 300 g kg^?1 and carbohydrate from 0 to 150 g kg^?1 of dry weight, according to a three‐component mixture design. Analysed values of protein and lipid were 500–770 g kg^?1 and 30–270 g kg^?1, respectively. Analysed carbohydrate levels were as added. Increasing levels of both lipid and carbohydrate had a positive effect on fish growth (P < 10^?3), whereas protein levels above 600 g kg^?1 gave a reduction in growth (P < 10^?4). The effects on growth were evident in fish less than 4 g, whereas fish growth between 4 and 6 g was unaffected by the dietary variation. It is hypothesized that the reduction in growth at high protein levels in fish of less than 4 g could be owing to incomplete utilization of protein, as the stomach of cod is not fully developed before the fish is approximately 1 g. Mortality and cannibalism were high in fish less than 4 g but low when the fish grew from 4 to 6 g. There was a significant decrease in cannibalism with increasing dietary lipid during the first half of the experiment (P < 0.05) and cannibalism was consistently high in fish fed less than 150 g kg^?1 lipid. The lipid level in whole fish increased with increasing dietary levels of lipid (P < 10^?6) and carbohydrate (P < 10^?4), whereas the liver lipid level increased with increasing dietary lipid up to 200 g kg^?1 (P < 10^?6) and decreased thereafter (P < 10^?4). Whole body glycogen increased slightly with increasing levels of dietary carbohydrate (P < 0.05) and was not affected by the other dietary variables. Liver glycogen increased in response to increasing dietary carbohydrate (P < 10^?5) and decreasing levels of dietary lipid (P < 10^?5). An abrupt increase in liver glycogen was seen with the reduction in dietary lipid from 100 to 50 g kg^?1. The hepatosomatic index increased in response to both dietary lipid and carbohydrate (P < 10^?6). It is concluded that the protein requirement of young cod is less than 500 g kg^?1 of dry diet. Fish of less than 4 g should not be given more than 620 g kg^?1 protein and should be supplemented with 150–200 g kg^?1 lipid. Carbohydrate up to 150 g kg^?1 of dry diet promoted growth and did not seem to affect the fish negatively. Fish above 4 g can be given diets varying in protein and carbohydrate over the wide range of concentrations used in the present study, but lipid supplementation should be restricted to between 100 and 200 g kg^?1.     

海州湾大泷六线鱼摄食生态研究

根据2011年3—12月在海州湾及其邻近海域进行的5个航次底拖网调查,通过分析531尾大泷六线鱼(Hexagrammos otakii)的胃含物样品,对其摄食生态进行了初步研究。结果表明,大泷六线鱼摄食的饵料种类有60余种,虾类、蟹类、双壳类是其最主要的3种饵料类群,优势饵料生物有东方缝栖蛤(Hiatella orientalis)、疣背宽额虾(Latreutes planirostris)和钩虾(Gammarus sp.)等;其食物组成存在明显的季节变化和体长变化,全年均大量摄食虾类,夏季还摄食一定量的蟹类,秋季摄食多毛类和头足类的比例较高。随着体长的增长,大泷六线鱼摄食的饵料生物由小型甲壳类逐渐转变为体型较大的虾类和鱼类。大泷六线鱼的空胃率和平均胃饱满指数存在明显的季节变化,春季空胃率最高,冬季空胃率最低;平均胃饱满指数春季最高,秋季最低。典范对应分析表明,体长是影响大泷六线鱼摄食的主要因子,其次是底层水温、叶绿素a和pH。     

A comparison among differently enriched rotifers (Brachionus plicatilis) and their effect on Atlantic cod (Gadus morhua) larvae early growth, survival and lipid composition

We evaluated the effect of differently enriched rotifers on the early growth, survival and lipid composition of Atlantic cod larvae (Gadus morhua). The enrichments tested were: (i) AlgaMac 2000^®; (ii) AquaGrow^® Advantage; and (iii) a combination of Pavlova sp. paste and AlgaMac 2000^®. Larvae from treatment 3 [1.50 ± 0.11 mg dry weight (dw) and 7.10 ± 0.14 dw specific growth rate (SGR)] were heavier (P = 0.006) and grew faster (P = 0.004) than larvae from treatment 2 (1.03 ± 0.04 mg dw and 6.29 ± 0.04 dw SGR). No significant differences were found in the final weight and SGR among larvae from treatment 1 (1.21 ± 0.07 mg dw and 6.58 ± 0.20 dw SGR) and larvae from treatments 2 and 3. The treatment 3 also resulted in the best survival at the end of the experimental period, estimated to be 3 on a scale from 1 to 5, whereas the survival estimates for the two other groups were 1–2. Larvae from the treatment 3 reached 37 days posthatch with levels of ω6DPA 32‐fold higher than newly hatched larvae. Differences in the larval enrichment of ω6DPA may explain the differences in growth and survival of the Atlantic cod larvae.     

Characterization of a Probiotic Lactobacillus fermentum Isolated from Snakehead,Channa striatus,Stomach

This study sought to isolate and characterize lactic acid bacteria (LAB) from stomach of adult snakehead fish, Channa striatus, to be used as probiotics for freshwater fish. A total of 13 strains were isolated from the stomach of 10 fish, and 4 of these belonged to LAB. Strain LAB‐3 showing highest in vitro growth inhibition of Aeromonas hydrophila in a disk diffusion test was identified as Lactobacillus fermentum by conventional and molecular techniques and evaluated in vitro through various tests. The bacterium could grow at pH 3–8; but the optimum growth was observed at pH 6. Moreover, LAB‐3 grew at 0.15 and 0.3% bile salt concentrations, from 15 to 45 C, and at 4% NaCl. L. fermentum showed in vitro inhibitory activity against three fish pathogens, A. hydrophila, Pseudomonas aeruginosa, and Shewanella putrefaciens, tested by disk diffusion and well diffusion methods. Antibiotic sensitivity tests indicated that L. fermentum was resistant to streptomycin, gentamycin, and kanamycin, intermediate to tetracycline, but sensitive to chloramphenicol, amoxicillin, and ampicillin. Challenge test by using A. hydrophila showed that survival of snakehead was significantly (P < 0.05) improved when 2 × 10⁶ LAB‐3/g was supplemented to the diet. Therefore, this study suggests that L. fermentum might be a promising probiotic in snakehead aquaculture .     

Proximate and Fatty Acid Compositions in Different Flesh Cuts of Cultured,Cultured Fasted,and Wild Pacific Bluefin Tuna (Thunnus orientalis)

This study was carried out to determine the differences in proximate and fatty acid (FA) compositions in different flesh cuts of the most valuable cephalic portion of cultured (full-cycle), cultured fasted (full-cycle), and wild Pacific bluefin tuna (PBT; Thunnus orientalis). Cultured fasted PBTs were fasted for 6 days to ensure empty stomachs during harvesting and to determine the influence of fasting on the lipid and FA composition in different flesh cuts. Significantly higher lipid contents were observed (p < 0.05) in the dorsal akami (lean part) and the ventral o-toro (very fatty part) flesh cuts in cultured and cultured fasted PBTs than in wild ones. However, monounsaturated fatty acid (MUFA) contents in all flesh cuts were significantly higher in cultured and cultured fasted PBTs than in wild PBT. Wild PBTs contained significantly higher (p < 0.05) polyunsaturated fatty acid (PUFA) contents than other cultured PBTs in all flesh cuts except for the dorsal akami and wakaremi (fatty part near dorsal fin) flesh parts, and contained higher n-3 FA content than other PBTs—especially docosahexaenoic acid (DHA, C22:6n-3)—in the lipid fraction from the dorsal chu-toro (medium fatty part), ventral akami, ventral chu-toro, o-toro, and in dark flesh cuts. The flesh quality of cultured or cultured fasted PBTs has the advantage of having a higher total amount of essential FAs than that of wild PBT.     

Gastric dilation and air sacculitis in Chinook salmon,Oncorhynchus tshawytscha (Walbaum); correlation of macroscopic and microscopic lesions,and relationship of the syndrome to glomerulonephritis and serum biochemistry

Macroscopic and microscopic assessment procedures were developed to evaluate the severity and enable diagnosis from histological samples, of gastric dilation and air sacculitis (GDAS) in Chinook salmon, Oncorhynchus tshawytscha. Stomachs and swim bladders were examined from young fish with experimentally induced GDAS and from larger fish with the syndrome held in commercial saltwater net‐pens. Fish fed a diet previously known to induce GDAS had significantly wider stomachs with decreased prominence of longitudinal stomach folds that contained larger amounts of fluid (P < 0.001), and thinner stomach walls with greater inter‐nerve distances (P < 0.001), than fish fed an alternative commercial diet not associated with the syndrome. These fish also had swim bladders that were more likely to be opaque and contain more fluid (P < 0.001). These observations correlated well with selected criteria for stomach tissue (P < 0.002) and swim bladder (P < 0.04) that could be evaluated microscopically. Four stomach measurements, primarily measurements of wall or partial wall thickness and inter‐nerve distances, were suitable for discriminating between affected and non‐affected fish. A stomach width ratio, that was independent of fish weight and highly correlated with macroscopic stomach measurements (P < 0.0001), was particularly useful; this ratio was derived from the distances between both the outer border of the muscularis mucosa and mesothelium of the serosal surface to the stratum compactum. Serum biochemistry parameters (osmolality, calcium and magnesium) did not differ between fish fed different diets, but serum creatinine concentration was correlated with the microscopic thickness of the muscularis externa of the stomach wall and the total stomach thickness (P < 0.001 and P < 0.003, respectively). A glomerulonephritis was also noted in these fish. The severity of the lesion was not significantly related to GDAS nor to any serum biochemistry parameter assayed however.