Effects of Fumonisin B1-Containing Feed on the Muscle Proteins and Ice-Storage Life of White Shrimp (Litopenaeus vannamei)

Juvenile (5.5–5.7 g) white leg shrimp were exposed to mycotoxin in one indoor trial by feeding fumonisin B₁ (FB₁) at levels from 0.2 to 2.0 μg g^?1 FB₁ for 30 days. Shrimp growth was affected after exposure to more than 0.6 μg g^?1 FB₁. Soluble muscle protein concentration decreased, and changes in myosin thermodynamic properties were observed in shrimp after 30 days of exposure to FB₁. Marked histological changes in tissue of shrimp fed a diet containing FB₁ at 2.0 μg g^?1 were also observed. Shrimp fed diets containing more than 0.6 μg g^?1 FB₁ showed greater decrease in shear forces after 12 days of ice storage.     

In vivo calcitropic effect of some vitamin D compounds in the marine Antarctic teleost,Pagothenia bernacchii

The Antarctic notothenioid, Pagothenia bernacchii, were found to have plasma total and free calcium levels, plasma inorganic phosphate and whole body calcium efflux rates which were similar to those seen in other teleosts. But total bone calcium was lower than reported for other teleosts. A single injection of vitamin D₃ (5 ng g^–1 fish) increased plasma total and plasma free calcium and these increases were associated with an increase in whole body calcium efflux and bone calcification. Conversely, the same treatment with 1,25-(OH)₂-D₃ reduced plasma free calcium. This seco-steroid also increased the specific activity of ⁴⁵Ca in bone at 40h post-injection but did not significantly effect total bone calcium, plasma total calcium or whole body calcium efflux. 25-OH-D₃ at the same dose had no effect on any of the parameters tested and none of the seco-steroids tested had any effect on plasma total inorganic phosphate. These data show that both D₃ and 1,25-(OH)₃-D₃ can have calcitropic effects in this marine teleost and that these two forms of vitamin D can exert different effects within the same species.     

The effect of total replacement of fish oil with DHA‐Gold® and plant oils on growth and fillet quality of rainbow trout (Oncorhynchus mykiss) fed a plant‐based diet

This study investigated the effect of the replacement of fish oil (FO) with DHA‐Gold (DHA‐G)‐supplemented plant oils (PO) in rainbow trout fed plant‐protein‐based diets. Five diets (450 mg g^?1 digestible protein and 150 mg g^?1 crude lipid) were fed to rainbow trout (initial weight 37 ± 0.5 g) for 12 weeks in a 15 °C recirculating water system. The lipid inclusion types and levels were FO, PO and PO with DHA‐G supplemented at 30 mg g^?1, 60 mg g^?1 or 90 mg g^?1 of the diet replacement for corn oil. Fish fed 90 mg g^?1 DHA‐G were significantly larger and consumed more feed than fish‐fed PO or FO (218 g and 2.6% bwd^?1 versus 181 g and 2.4% and 190 g and 2.3%, respectively). Feed conversion ratio was significantly increased in fish fed 90 mg g^?1 DHA‐G (0.99) as compared to fish‐fed FO (0.90) and 30 mg g^?1 DHA‐G (0.91). Panellists found trout fillets from fish fed the 90 mg g^?1 DHA‐G diet to have significantly fishier aroma and flavour than fish fed the FO diet. Fatty acid analysis demonstrated that 60 mg g^?1 or 90 mg g^?1 DHA‐G supplementation increased PO fed fish fillet DHA to fatty acid levels equivalent or higher than those fish fed a FO diet.     

Effects of dietary Lactobicillus plantarum on the growth,carcass quality,and immune response of African catfish (Clarias gariepinus) challenged with Salmonella typhi

An experiment was conducted to investigate the effects of Lactobacillus plantarum on the production of African catfish (Clarias gariepinus). Five experimental diets containing 0, 10³, 10⁵, 10⁷, and 10⁹ CFU of Lactobacillus plantarum g^?1 diet (T₁–T₅ treatments respectively) were fed to African catfish (Clarias gariepinus) (9.20 ± 0.1 g initial body mass), for 70 days. Results indicated significantly lower growth performance in the fish fed diet without probiotics and in those fed diet with the least probiotic level. Treatments with probiotics significantly improved the blood profile and carcass protein but significantly reduced the carcass fat (P < 0.05); these treatments also marginally improved the carcass minerals in comparison with the treatment without probiotic (P < 0.05). Challenging the fish fed the experimental diets with Salmonella typhi showed higher immunity of fish fed the probiotic diets than those fed the nonprobiotic diet. Duncan’s multiple range test showed that the best fish performance was observed with 10³ CFU g^?1 L. plantarum for very parameter measured. However, regression analyses showed the optimum level of the bacteria to be 10^4.13–10⁵ CFU g^?1     

Relative bioavailability of zinc in supplemental inorganic and organic sources for Nile tilapia Oreochromis niloticus fingerlings

A 90‐day feeding experiment was conducted with sex reversed Nile tilapia (Oreochromis niloticus) fingerlings fed purified or practical diets supplemented with different zinc sources to evaluate fish growth performance and zinc and iron retention in fish bones, fillets, liver, skin and eyes. The relative bioavailability value (RBV) of zinc in the supplemental sources tested was also calculated. Fish were fed with isonitrogenous and isoenergetic purified or practical diets supplemented with 150 mg Zn kg^?1, as zinc sulphate monohydrate (ZnSO₄), zinc oxide (ZnO) or zinc amino acid complex (Zn‐AA). The feeding trial was conducted in 30, 50 L aquaria where four 0.66 ± 0.01 g (mean ± SD) fingerlings were initially stocked. No significant differences were observed for any growth performance variables (P > 0.05). In practical diets, only ZnSO₄ and ZnO presented bone zinc retention similar to that for the standard zinc source. Zinc concentration in the bone of fish fed practical diet supplemented with Zn‐AA (171 ± 3.62 μg g^?1) was significantly lower than that verified for the practical diets supplemented with the standard zinc source (200 ± 17.7 μg g^?1) or with ZnSO₄ (204 ± 19.9 μg g^?1). Assuming the concentration of zinc in bones as the response criterion, the supplemental zinc RBV from ZnSO₄ (105%) was higher than the RBV for Zn‐AA (95.1%) or ZnO (94.9%). Iron concentration in the bones of animals fed the non‐zinc‐supplemented purified diet was significantly higher than that observed for purified diet supplemented with Zn‐AA (P < 0,05). The results of the present work allowed us to conclude that ZnSO₄ in relation to ZnO or Zn‐AA was the supplemental zinc source with higher zinc bioavailability to Nile tilapia.     

Dietary vitamin E requirement for maximizing the growth,conversion efficiency,biochemical composition and haematological status of fingerling Channa punctatus

The effect of feeding graded levels of vitamin E (E₀, E₂₀, E₄₀, E₆₀, E₁₀₀, E₁₄₀, E₁₈₀, E₂₂₀, E₂₆₀) in nine casein–gelatin‐based isonitrogenous (450 g kg^?1 crude protein) and isoenergetic (17.97 kJ g^?1 gross energy) experimental diets was evaluated in fingerling Channa punctatus for 12 weeks. Growth, nutritional and haematological parameters were studied. Hepatic lipid peroxidation as thiobarbituric acid‐reactive substances (TBARS) was also assayed. The maximum absolute weight gain (AWG g/fish, 55), best feed conversion ratio (FCR, 1.32), protein retention efficiency (PRE, 40%) and energy retention efficiency (ERE, 76%) were achieved in fish fed on a diet supplemented with 140 mg vitamin E kg^?1 diet (E₁₄₀). A consistent decline in the hepatic TBARS concentration and an improvement in haematocrit (Hct) and haemoglobin (Hb) were displayed in fish fed on diets with increasing concentrations of vitamin E up to 140 mg kg^?1 (E₀–E₁₄₀), beyond which (E₁₈₀–E₂₆₀) a reverse trend in these parameters was evident. Based on the broken‐line regression and exponential analyses of AWG, FCR, PRE, ERE, Hb and Hct data, diets for fingerling C. punctatus should contain vitamin E in the range of 140–169 mg kg^?1 to maintain satisfactory fish performance.     

An evaluation of the duration of efficacy of emamectin benzoate in the control of Caligus curtus Müller infestations in Atlantic cod, Gadus morhua L

The duration of efficacy of emamectin benzoate in the control of Caligus curtus infestations in Atlantic cod, Gadus morhua L., was studied following an administration of 50 μg kg^?1 for seven consecutive days. No lice were found on medicated fish when challenged 1 week (challenge 1) or 5 weeks (challenge 2) following termination of medication, whereas the mean abundance of lice among the unmedicated fish was 17.9 and 19.3 lice per fish in challenge 1 and 2, respectively. Muscle concentrations of 19.5 ± 8.2 ng g^?1 and 3.4 ± 0.9 ng g^?1, respectively, and skin concentrations of 23.1 ± 10.8 and 4.2 ± 1.0 ng g^?1, respectively, were found 27 and 55 days following the termination of medication. Tissue concentrations and the duration of efficacy indicate a dosing regime for emamectin in cod, similar to the regime used for Atlantic salmon, Salmo salar L.     

Toxicity of cultured puffer fish and seasonal variations in China

To confirm the toxicity or the tetrodotoxin (TTX) content of cultured puffer fish in China, 565 specimens of cultured puffer fish (Takifugu rubripes, Takifugu fasciatus or Takifugu obscurus, Takifugu flavidus and Takifugu bimaculatus) were collected from five provinces from November 2007 to November 2008. The toxicity of the skin, muscle, liver and testis/ovary was examined using methods based on a mouse assay for TTX. The results indicated that the skin, muscle, liver and testis of specimens were ‘non‐toxic’ in both of the mouse assays [<10 mouse unit (MU) g^?1 or 2.2 μg g^?1] from the viewpoint of food hygiene. However, TTX was detected from an ovary sample of the cultured T. rubripes collected from the Shandong province in March 2008, which was 125.43 MU g^?1 tissue. The average TTX contents in the muscle, liver and skin of T. rubripes from Hebei and Shandong provinces were the highest in May or July (1.31, 0.90 and 0.62 MU g^?1, respectively, in Hebei, and 1.57, 0.32 and 0.16 MU g^?1, respectively, in Shandong) and the lowest in January (<0.1 MU g^?1 or 0.02 μg g^?1). Thus, non‐toxic cultured puffer fish could be produced successfully in mainland China.     

Effect of dietary protein-energy levels and fish initial sizes on growth rate, development and production of Nile tilapia, Oreochromis niloticus L.

The effects of dietary protein‐energy levels on the growth rate, proximate composition and production were examined in Nile tilapia, Oreochromis niloticus, at two starting weights (22.9 and 39.8 g) reared in concrete ponds for 180 days. The highest weight gain (183.1 g) was obtained with fish fed a 30% protein and 10.5 kJ g^?1 diet for the small initial size and 180.2 g for a diet containing 25% protein and 12.6 kJ g^?1 for the large initial size. Dressed yields (edible mass) and fillets increased to 56.9% and 52.5% in fish fed diet with 25% protein and 10.5 kJ g^?1 at the initial size of 22.9 g, while fish started at 39.8 g exhibited the best values (56.5% and 52.1%) when fed the 30% protein and 10.5 kJ g^?1 diet. Proximate composition of soft tissue (wet weight basis) in small fish was significantly influenced by dietary protein‐energy levels. Protein was 26.1±0.3% in fish fed the high protein (30%) and low energy (10.5 kJ g^?1 diet), while lipid content was 6.4±0.3% at diet containing 20% protein and 14.7 kJ g^?1 diet. Large initial size fish fed the diet with 25% protein and 14.7 kJ g^?1 had the highest body protein (32.0±0.4%) and lowest lipid content (2.2±0.3%). Feed conversion ratio (FCR) and protein efficiency ratio varied with different dietary protein‐energy levels and initial fish sizes. Feed conversion ratio increased with increasing protein and decreasing energy level in the diet, and values in small fish were higher than values in large fish. Protein efficiency ratio decreased with increasing dietary protein level and decreasing energy level. The maximum total production (7.6 tons feddan^?1) was with dietary high protein (30%) and low energy (10.5 kJ g^?1) for small‐sized fish, while large initial fish had the highest production (3.7 tons feddan^?1) when fed the 25% protein and 12.6 kJ g^?1 diet energy. Starting with 22.9 g fish was more advantageous than the initial size of 39.8 g for rearing Nile tilapia. Small fish required a high‐protein and low‐energy diet, whereas large fish required a low‐protein and high‐energy diet to achieve highest production.     

Bovine placental lactogen invokes rapid growth in chinook salmon

The effect of recombinant bovine placenta) lactogen (rbPL) treatment upon growth of juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum) (14.0 ± 0.31 g wet wt), was examined over a period of 6 weeks. Experimental animals were either injected (5 μg rbPL g^?1 week^?1), implanted with a cholesterol pellet containing 0.4 mg rbPL (approximately 4 μg g^?1 week^?1), or orally and rectally intubated with 7.5 μg rbPL g^?1 week^?1. Control animals were injected with bovine serum albumen (BSA), 5 μg g^?1 week^?1, implanted with a placebo or orally intubated (7.5 μg BSA g^?1 week^?1). Significant (P < 0.05) growth acceleration was recorded for rbPL-injected and pellet-implanted groups from week 2 onwards when compared against all other groups. Oral or rectal intubation of rbPL (7.5 μg rbPL g^?1 week^?1), however, was without effect. Condition factor decreased in all groups, but was significantly lower in rbPL-injected and pellet-implanted fish at trial end when compared against controls. No differences were recorded between groups for per cent body moisture or relative gut length. Hepatosomatic index was significantly (P < 0.05) higher in rbPL-injected and rbPL-implanted chinook salmon versus other fish.     

Effects of low and medium levels of red alga Nori (Porphyra yezoensis Ueda) in the diets on growth,feed utilization and metabolism in intensively fed Nile tilapia,Oreochromis niloticus (L.)

A 10‐week feeding experiment was conducted in a respirometric system to evaluate the suitability of red alga Nori (Porphyra yezoensis) as a partial replacement for fish meal in intensively fed Nile tilapia. Diets were formulated to be iso‐nitrogenous and iso‐energetic and to replace 0%, 15% and 30% fish meal with Nori, P. yezoensis. No statistically significant differences in growth or feed utilization between the control diet and either Nori diet were found. Tilapia fed on Nori 15 increased their body mass by 415%, those fed the control diet by 341% and fish fed Nori 30 by 317% over the experimental period. Nori 15 fed fish showed the best feed utilization, highest metabolic growth rate and significantly lower oxygen consumption rates than the control. Both Nori supplemented groups (Nori 15: 4.1 g O₂ g^?1 protein gain and Nori 30: 3.9 g O₂ g^?1 protein gain) used less oxygen per gram of protein gain compared to fish fed the control diet (5.4 g O₂ g^?1 protein gain). Our results show that a low replacement level (15%) of fish meal with Nori improves growth and feed utilization while oxygen consumption and amount of oxygen consumed per gram protein gain are significantly decreased.     

Dietary Lactobacillus plantarum supplementation decreases tissue lead accumulation and alleviates lead toxicity in Nile tilapia (Oreochromis niloticus)

Pollution by the heavy metal lead (Pb) has become a threat to both aquaculture and food safety. In this study, the protective effects of a selected probiotic with good Pb binding capacity (Lactobacillus plantarumCCFM8661) against waterborne Pb exposure were evaluated in Nile tilapia (Oreochromis niloticus). One hundred and eighty fish were divided into four groups as control, Pb‐only, Pb‐plus‐CCFM8661 and CCFM8661‐only. Fish were exposed to a dose of waterborne Pb level at 1 mg L^?1 for 4 weeks, and the probiotic was administered at 10⁸ CFU g^?1 in fish diet twice daily. The results showed that dietary supplementation of CCFM8661 ameliorated the growth performance and prevented the death of Pb‐exposed fish. Cotreatment with Pb and CCFM8661 also effectively decreased Pb accumulation in kidney, liver, gonad, brain, gills and muscle. Moreover, the administration of this probiotic alleviated Pb‐induced oxidative stress, recovered digestive enzyme activities and blood δ‐aminolevulinic acid dehydratase activity, reversed alterations in innate immune status and decreased the frequencies of the nuclear abnormalities in peripheral blood erythrocytes of fish. These results suggested that CCFM8661 may be a novel dietary supplement against Pb toxicity at least in tilapia.     

The fate of chlortetracycline residues in a simulated chicken–fish integrated farming systems

Two experiments were conducted at the Asian Institute of Technology, Pathumthani, Thailand to investigate the fate of chlortetracycline (CTC) residue in chicken manure and its effect on integrated chicken–fish farming system. During the first experiment, broiler chickens were raised and CTC residues in their manure were analysed. Chicken fed diets containing 0, 50, 200 and 800 CTC mg kg^?1 had CTC residue levels of 0, 0.9, 3.8 and 6.5 CTC ng g^?1. Once the diet containing CTC was withdrawn, CTC in the manure dropped to negligible amounts (0, 0, 0.2 and 0.5 CTC ng g^?1) within 1 day. Integrated chicken–fish farming systems were simulated during the second experiment to determine the fate of antibiotic residues in chicken manure in aquaculture environment. Chickens were fed a CTC‐free diet and a feed containing CTC at 200 mg kg^?1. Ten 4 m³ square concrete tanks (2 × 2 × 1 m) were used for the experiment. Five tanks were fertilized with CTC‐contaminated manure and the remaining five tanks were fertilized with CTC‐free manure at a rate of 100 kg dry matter ha^?1 day^?1. Sex‐reversed Nile tilapia (Oreochromis niloticus) was stocked at 12 fish tank^?1 on the 14th day after chicken manure application. The immuno‐radio microbial receptor assay (Charm II test) revealed that edible fish muscle, fish intestinal tract and sediment were contaminated by CTC at rates of 7.21, 22.104 and 1.788 ng g^?1, respectively, after 45 days. Chlortetracycline was detected on day 20 in the water column and gradually increased from 0.26 to 12.13 ng g^?1. Chlortetracycline residues were not detected in fish or the aquatic environment of the CTC‐free treatment. The results demonstrate the potential for antibiotic residue accumulation in fish and aquatic environment when CTC‐contaminated chicken manure is used for pond fertilization.     

Carotenoid Pigments Composition of Two Commonly Discarded Decapod Crustaceans in Grand Sole and the Galician-Northern Portugal Coast Fisheries

ABSTRACT

Carotenoid composition of two commonly discarded decapod crustaceans, Liocarcinus depurator and Munida spp., was assessed in different catching months. Total carotenoid content ranged between 7 ± 1 and 22.4 ± 0.7 μg g^?1. Pigment separation was performed by high-performance liquid chromatography coupled with a diode array detector. Astaxanthin accounted for 21 to 50% of total carotenoids, and the remaining percentage corresponded mainly to esters of astaxanthin. The fatty acid profile of carotenoid extracts for each species was evaluated. Overall total unsaturated fatty acids content ranged from 406 to 1,631 μg g^?1. Both species were rich in omega-3 fatty acids, which on average represented 68% of total unsaturated fatty acids. Therefore, the use of these low value by-catch species as a source of carotenoid pigments and fatty acids (e.g., for aquaculture formulations) is a possible alternative to their disposal at sea.     

Dietary histidine affects lens protein turnover and synthesis of N-acetylhistidine in Atlantic salmon (Salmo salar L.) undergoing parr–smolt transformation

This study was conducted to investigate protein synthesis rates and metabolism of histidine (His)‐derivatives in lenses of Atlantic salmon (Salmo salar L.) of different dietary His background during parr–smolt transformation. Two populations of Atlantic salmon parr of equal origin were established in freshwater (FW), 3 months prior to transfer to seawater (SW). The populations were fed either a control diet (CD) containing 8.9 g kg^?1 His or the same diet added crystalline His to a total level of 14.2 g kg^?1 (HD). On the basis of these two populations, ¹⁴C His force‐feeding studies were performed; in FW 3 weeks prior to sea transfer and in SW 6 weeks after transfer. The studies were conducted by force‐feeding the respective diets enriched with ¹⁴C labelled His, with subsequent measurements of incorporation of ¹⁴C His into lens free amino acid pool, as well as into lens proteins and other free His pool fractions. The latter included the major lens imidazole N‐acetylhistidine (NAH). Lens concentrations of His and NAH were clearly influenced by dietary His history, both in parr and smolt. The lens His and NAH concentrations in the CD population were considerably lower in SW than in FW, while in the HD group the His level was equal and the NAH level 50% higher in SW than in FW. Fractional synthesis rate for NAH, K_{S (NAH)}, in FW was 8.2 and 4.2 μmol g^?1 day^?1 for fish in the CD and HD populations, respectively. The corresponding K_{S (NAH)} values in SW were 5.1 and 33.0 μmol g^?1 day^?1. Our data show that free His is rapidly converted to NAH in the lens, and that NAH seems to have a very high turnover, especially in salmon reared in SW. Fractional synthesis rate for lens proteins, K_{S (PROTEIN)}, ranged between 1.8 and 17.3% day^?1 (182 and 2791 μg g^?1 day^?1, respectively), and was generally higher in SW than in FW (P < 0.01). In SW, K_{S (PROTEIN)} was highest in fish in the HD population (P < 0.05), whereas lens protein retention in the HD group was significantly lower than the CD group (P = 0.01). In a second model assuming that His from lens NAH is available for protein synthesis, calculated values of K_{S (PROTEIN)} ranged between 0.17% day^?1 (17.6 μg g^?1 day^?1) and 0.48% day^?1 (70.2 μg g^?1 day^?1). Cataract scores recorded in the His populations at a later point (day 204), showed that the CD fish had significantly higher mean cataract scores than individuals in the HD population (P < 0.01), confirming that low levels of lens His and NAH are associated with cataract development.     

Effects of dietary propolis supplementation on growth performance, immune responses, disease resistance and body composition of juvenile eel, Anguilla japonica

This study was conducted to investigate the effects of dietary propolis supplementation on growth performance, immune responses, disease resistance and body composition of juvenile eel, Anguilla japonica, in order to evaluate its bioavailability as a feed additive for this species. A total of 540 fish averaging 7.7?±?0.22?g (mean?±?SD) were randomly distributed into 18 tanks in groups of 30, and each tank was then randomly assigned to one of three replicates of six diets containing 0 (P₀), 0.25 (P_0.25), 0.5 (P_0.5), 1.0 (P₁), 2.0 (P₂) and 4.0 (P₄) % dietary propolis. At the end of 12?weeks of feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) of fish fed P_0.5 diet were significantly higher than those of fish fed P₀, P₁, P₂ and P₄ diets (P?<?0.05). These parameters were 148.9%, 0.72% day^?1, 94.4% and 2.9, respectively for fish fed P_0.5 diet. Serum lysozyme activity of fish fed P_0.5 (105.7 units mL^?1) and P₁ (106.0 units mL^?1) diets were significantly higher than those of fish fed P₀, P_0.25, P₂ and P₄ diets. Mucus lysozyme activity of fish fed P₁ (8.4 units 10?cm^?2) diet was significantly higher than those of fish fed P₀, P₂ and P₄ diets. Results indicated that the optimum dietary propolis supplementation levels could be 0.25?C0.5% for optimum growth and feed efficiency, and 0.5?C1% for enhanced immune responses and disease resistance in eel, A. japonica. This study may suggest that the dietary propolis level for the optimum immune responses could be higher than the level for the optimum growth of eel.     

Presence and distribution of PAHs,PCBs and DDE in feed and sediments under salmon aquaculture cages in the Bay of Fundy,New Brunswick,Canada

• 1. Wastes from feed and faeces can result in the deposition of contaminants in sediments around aquaculture sites. Five types of feed pellet, a commercial fish oil and 76 sediment samples collected under and up to 100 m away from salmon aquaculture cages in the south‐western Bay of Fundy between 1998 and 2000 were analysed for polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and chlorinated pesticides.
• 2. Five alkylated naphthalenes (aNAs) were consistently detected in fish oil (116–180 ng g^?1, per aNA), in pellets (25–51 ng g^?1, dry weight, per aNA), and sediments (<1–45 ng g^?1, dry weight, per aNA). Other PAHs were detected at variable levels in feed or in sediments.
• 3. IUPAC congener 153 (a PCB) and p,p′‐dichlorodiphenyldichloroethylene (p,p′‐DDE) were detected more frequently than other chlorinated targets in oil (108 ng g^?1 and 176 ng g^?1 respectively), feed (<1–14 ng g^?1 and 1.7–28.2 ng g^?1 respectively) and sediments (<0.08–3 ng g^?1 and <0.5–7 ng g^?1 respectively).
• 4. Trends were observed during the first year of sediment sampling (1998), with higher organic carbon, PCBs and p,p′‐DDE levels below the cages than 50 m away. The PAHs other than aNA showed an opposite trend with distance. In 1999, levels of p,p′‐DDE and PCBs were somewhat reduced under the cages, but were detected up to 100 m away from the cages.
• 5. Levels of aNA tended to be higher at some sites in 1999 relative to 1998, reflecting variability in feed and/or differential transport or degradation of contaminants relative to the environmental background. When detected, mean levels of PCBs and DDE were 2–10 times lower in 2000 than in 1999, and PAHs were 30–40% lower in 2000 than in 1999.
• 6. Interpretation of the results is done cautiously, since the exact locations of the sites sampled is only known to an intermediate facilitating the work between farmers and scientists. Levels of contaminants are compared with international results, interpreted relative to potential toxicity, uptake from feed, from deposited sediments, and in the framework of an aquaculture decision‐support system published recently.

Copyright © 2005 John Wiley & Sons, Ltd.     

Characterization of whitebait (Galaxias maculatus) respiratory rates to optimize intensive culture carrying capacities

Galaxias maculatus is an osmeriform native fish of the Southern Hemisphere, in which the crystalline larvae is considered as a luxury delicacy, for this reason, it has been commercially exploited in Chile, Argentina and New Zealand. However, the fisheries have been rapidly decreasing due to the overexploitation and the predation of introduced species. Because of these events, there is a need to determine a carrying capacity for an intensive fish culture. In order to optimize stocking densities for fish culture, this paper proposes objectives to determine oxygen consumption (OC) rates, dissolved oxygen concentrations that produce signs of hypoxia and the average time elapsed between food intake and peak OC in G. maculatus. In the oxygen experiments under routine metabolism conditions, we found that G. maculatus adults and whitebait showed signs of asphyxia at dissolved oxygen concentrations between 1.3 and 2.2 mg L^?1 and that adults tolerated dissolved oxygen levels as low as 1.3 mg L^?1. The results showed that G. maculatus individuals with an average weight of 0.04 g consumed 0.048 mg O₂ h^?1, whereas individuals with an average weight of 1.4 g consumed 0.345 mg O₂ h^?1. Galaxias maculatus increased the OC rate by 31%, from 0.39 to 0.51 mg O₂ h^?1 g^?1, occurring 14 min after food intake. The carrying capacities for industrial cultures of G. maculatus, were estimated using an allometric equation (OC=0.2363 ×W ^0.612 ), a water flow rate of 1 m³ h^?1 and an input oxygen concentration of 10 mg L^?1 at 12 °C. The density culture of whitebait (4 g) can be allowed to reach 8–11 kg m^?3; therefore, these stocking densities reduce the risk of hypoxia and mortality, ensuring the appropriate growth and feed conversion rates.     

Magnesium requirement of Atlantic salmon (Salmo salar L.) parr in seawater-treated fresh water1

This experiment was undertaken to establish the magnesium (Mg) requirement in young Atlantic salmon, Salmo salar L., in seawater-treated fresh water. In Norwegian hatcheries it is a common practice to add sodium hydroxide and/or sea water (1–2%) to improve pH and conductivity of the natural fresh water. Parr with initial weight of 8 g, were divided in six triplicate groups in brackish water containing 54 mg Mg L^?1 and fed a basal casein-gelatine diet supplemented with minor amounts of krill and fish meal (containing 200 mg Mg kg^?1) for an initial period of 3 weeks. Thereafter the fish were fed this diet supplemented with either 0, 100, 200, 300, 400 or 500 mg Mg kg^?1 (as MgSO₄) for 12 weeks. Growth and feed efficiency were recorded. Concentrations of Mg and other divalent cations (Ca and Zn) were measured in whole fish, serum and vertebrae. Sodium concentration in vertebrae was also measured. Growth and feed efficiency were unaffected by the levels of dietary magnesium used in the experiment. Magnesium concentrations in the whole body, serum and vertebrae Mg appeared to be more sensitive than growth and feed efficiency to differences in dietary Mg intake. The group fed the unsupplemented diet showed significantly lower Mg concentration in these tissues than the other groups. Whole-body calcium concentration was negatively correlated with dietary Mg and Ca:Mg ratios in the vertebrae were significantly affected by the dietary Mg levels. Zinc concentration in whole body, serum and vertebrae was not altered by the dietary Mg levels. Further, vertebral Na concentration did not vary between the dietary treatments. In conclusion, a minimum Mg supplementation level of 100 mg kg^?1 dry diet (in total, 326 mg kg^?1) was needed to maintain Mg concentration in the whole body and serum and for proper bone mineralization.     

Effect of replacement of dietary fish meal by meat and bone meal and poultry by-product meal on growth and feed utilization of gibel carp, Carassius auratus gibelio

Triplicate groups of gibel carp Carassius auratus gibelio (initial body weight: 5.25 ± 0.02 g) were fed for 8 weeks at 20–25 °C on five isonitrogenous (crude protein: 400 g kg^?1) and isoenergetic diets (gross energy: 17 kJ g^?1). Meat and bone meal (MBM) or poultry by‐product meal (PBM) were used to replace fish meal at different levels of protein. The control diet contained fish meal as the sole protein source. In the other four diets, 150 or 500 g kg^?1 of fish meal protein was substituted by MBM (MBM₁₅, MBM₅₀) or PBM (PBM₁₅, PBM₅₀). The results showed that feeding rate for the MBM₅₀ group was significantly higher than for other groups except the PBM₅₀ group (P < 0.05). Growth rate in the MBM₁₅ group was significantly higher than that in the control (P < 0.05), while there was no significant difference in growth between the control and other groups (P > 0.05). Feed efficiency and protein efficiency ratio in MBM₅₀ was significantly lower while that in MBM₁₅ was significantly higher (P < 0.05). Replacement of fish meal by MBM at 500 g kg^?1 protein significantly decreased apparent dry matter digestibility (ADC_D) and gross energy (ADC_E) while apparent protein digestibility (ADC_P) was significantly decreased by the replacement of MBM or PBM (P < 0.05). The results suggest that MBM and PBM could replace up to 500 g kg^?1 of fish meal protein in diets for gibel carp without negative effects on growth while 150 g kg^?1 replacement by MBM protein improved feed utilization.