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Tengiliður

Jónas Baldursson

Verkefnastjóri

jonasb@matis.is

This report provides initial identification of utilization alternatives for liver, viscera and swim bladders of silver carp harvested in the Illinois River. The report was contracted by Íslenski Sjávarklasinn as part of a larger consultancy work on utilization alternatives for carp in the Great lakes.

Mass balance and chemical analysis was made on samples of silver carp, from which suggestions for utilization alternatives were based on. The proportions of liver and viscera of the whole fish that was analyzed in this study was 2.5 ± 0.6% and 4.9 ± 1.5% with a fat content of 3.1% and 7.5% respectively.

The utilization alternatives identified include that the liver and viscera could be processed into fish meal and oil, or processed into fish silage. Fish meal and oil production is highly dependent on volume since the investment and production cost is most likely high and a better alternative would be to process all rest raw material originating from Asian carps in a specific location together to increase the capacity of the production. Producing fish silage has lower investment and production cost and can better preserve the rest raw material until further processing.

The swim bladder has an opportunity of being processed further into either dried swim bladder for human consumption or for collagen products used in the health industry. More studies on collagen yield from silver carps is needed to estimate what revenues can be achieved.

This report is to be considered as an initial identification of utilization alternatives. Further analysis is needed to determine the applicability of the alternatives identified.

Skýrslan er lokuð / This report is closed

Tengiliður

Undesirable substances in seafood – results from the Icelandic marine monitoring activities in the year 2020

This report summarises the results obtained in 2020 for the screening of various undesirable substances in the edible part of Icelandic marine catches.

The main aim of this project is to gather data and evaluate the status of Icelandic seafood products in terms of undesirable substances and to utilise the data to estimate the exposure of consumers to these substances from Icelandic seafood and risks related to public health. The surveillance programme began in 2003 and was carried out for ten consecutive years before it was interrupted in 2013. The project was revived in March 2017 to fill in gaps of knowledge regarding the level of undesirable substances in economically important marine catches for Icelandic export. Due to financial limitations the surveillance now only covers screening for undesirable substances in the edible portion of marine catches for human consumption and not feed or feed components. The limited financial resources have also required the analysis of PAHs, PBDEs and PFCs to be excluded from the surveillance, providing somewhat more limited information than in 2013. However, it is considered a long-term project where extension and revision is constantly necessary. 

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Different colourant and colourant inclusions in diets for Atlantic salmon and its effect on flesh colour was tested. Experimental diets of similar nutritional composition, but different colourant sources and inclusions were produced in commercial fish feed mill (Laxa ltd.). Panaferd-AX colourant was compared to standard colouring regime using Lucantin® Pink  (30/60/50mg/kg) as a control. Atlantic salmon were fed these diets in a growth trial in experimental tanks in saline water for 438 days.

The original plan was to test the colourant Aquasta® in addition but since its production was halted, it was only used in the first phase of the experiment. The continuing experiment compared Panaferd in different inclusion and Lucantin® Pink. Initially The recovery of the colorants in the experimental feed production was tested. Using Panaferd, the recovery of astaxanthin was only 76,9% after feed processing and extrution compared to 100+% recovery using Lucantin. Therefore the experimental diets were added plus 30% colourantsto ensure astaxanthin level according to feed analyses.

To adjust planned colourant consumption the feeding was mixed with unpigmented basal diet. The growth, feed intake and feed conversion were similar between groups, and no mortalities were related to treatments during the experimental period.

The flesh colour was measured by DSM Salmofan®, Konica Minolta CR-400 Chroma Meter and by chemical analyses of astaxanthin and sum of carotenoids. Only small differences were found in visual filet pigmentation, measured by Salmofan and Konica Minolta Chromo Meter, between the different colouring regimes. The filet colour was considered acceptable in all treatment groups. The correlation between chemically analysed content of carotenoids, including astaxanthin, and visual colour score of the filets was poor.

In conclusion: all tested regimes and carotenoid content in the diets for Atlantic salmon resulted in acceptable fillet colour.

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This study mainly aimed at researching dietary effects on growth and important quality characteristics of Arctic charr, lipid composition and flesh color. The first object of this study was to investigate the effect of different lipid sources and lipid ratio in diets on growth and chemical composition in fillets. The second object was to investigate the effect of different colorant sources in diets and colorant feeding combinations on flesh color in fillets. Two long-term experimental trials (1= 250 days; 2=268 days) were run in saline water (approx. 12-18ppt) with initial weight of fish above 100+g in both trials. The water temperature was in the range of 6-9°C in the first but 8,5-10,5°C in the second trial.

1. Different dietary lipid ratio and lipid sources did not affect the fish growth, growth rate, feed consumption, FCR or harvesting output. The dietary lipid content and composition was reflected by lipid content in fillets. The fatty acid composition in the diets was reflected fatty acid composition of the fillets. The most important difference was in the content of the long chain n-3 and n-6 fatty acids and n-3/n-6 fatty acid ratio between groups fed fish oil or mix of plant oil sources. Lipid source or volume in diets only had minimal effects on other nutritional components analysed in fillets. The different dietary lipid sources and ratio was considered to have rather small effect on visual fillet color, although some existing variation related to analytical methods.

2. Analysis of carotenoids in the experimental diets showed difficulties in producing diets containing exact carotenoid content, according to plan and formulation, regardless of colorant types. The feed processing, lack of stability of the sensitive carotenoids or inaccurate content description of the colorant sources led to varying recovery of estimated concentration in the diets. Therefor the feeding and regimes needed to be adjusted by mixing daily ration with uncolored diets. Consumed colorants were calculated according to diet color content and consume. The growth rate, FCR and harvesting output was similar in all groups. The fish was grown to an average size of 1800g. Maturity ratio (indication of maturity) was in the range of 11-24% but mature fish were intentionally avoided in the estimates of fillet color and chemical composition. Minimal differences were detected in visual fillet color (Salmofan), but fillet color measured by Minolta Chromatography showed more relation in fillet color and consumed carotenoids in diets. Carotenoid analysis in fillets correlated to carotenoid consumption. Beneficial effects of increased carotenoid content in diets above 50 mg/kg were not detected in visually more reddish fillets.

The overall aim of this study was:

• Estimate the effect of lipid content (energy) and lipid sources in diet on growth and feed efficiency of Arctic charr.
• Estimate the effect of dietary fat sources on fat composition and flesh quality of Arctic charr.
• Evaluation of economically feasible and efficient utilization of colorants in fish diets and interactions with fat content in diet and fish.
• Decrease production cost in Arctic charr culture.

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