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1. Nutrition and Seafood Safety by Dr. Øyvind Lie, Director of National Institute of Nutrition and Seafood Research, Bergen, Norway (E-mail: oyvind.lie@nifes.no).

Dr. Lie’s paper was largely centered on the complexity of issues relating to food safety of aquaculture products in Europe. He noted that most feed safety regulations were developed for terrestrial livestock and applied as such for aquatic animals. Explaining that risk assessment of additives and contaminants in animal feed included four elaborate steps namely, hazard identification; hazard characterization; exposure assessment; and risk characterization, he stated that the risks must be evaluated from the perspective of the animal health, human health, user safety and environment. He proceeded to give several case studies of contaminants such as arsenic, dioxins and brominated flame retardants which have undergone some level of risk assessment. Finally, he spoke about the challenges in seafood safety which included the severe lack of data on nutritional toxicity of a wide range of contaminants and the need for tools and models for risk assessment of fish feed contaminants.

2. The Effect of Feeding Diets Containing Marine Fish Oil or Vegetable Oils on Dioxin and Dioxin-like PCB Content of Farmed Salmon Flesh by Dr. Gordon Bell of Lipid Nutrition Group at Stirling University, Scotland, UK (E-mail: g.j.bell@stir.ac.uk).

Dr. Bell presented the results of a trial in which Atlantic salmon were fed four diets containing either 16% or 35% of fish oil or vegetable oil. The vegetable oil was a 1:1 blend of rapeseed and linseed oil. The fish were fed the experimental diets from first feeding to 2 kg. Afterwards the fish were fed a finishing diet containing 35% of fish oil for six months. Dioxin and dioxin-like PCB concentrations were measured in the diets and flesh samples. The results of the study were as following:

• The dioxin concentration of fish fed high fish oil diet was 0.53 ng TEQ/kg, which was well below the maximum limit of 4 ng TEQ/kg set by the European Union.
• Use of vegetable oils significantly lowered the dioxin concentrations in the flesh. The 2 kg fish fed high vegetable diets had only 25% of dioxin concentration compared to fish fed the high fish oil diet. After being on the high fish oil finishing diet for 6 months, the fish had only 37% of dioxin concentration compared to the fish that were on the high fish oil diet throughout the culture cycle.
• While the concentrations of the contaminants in the diets positively correlated with the concentrations of the contaminants in the fish fed the diets, the concentrations of the contaminants in the flesh were always lower than corresponding feed concentrations.
• Growth rate and feed conversion efficiency of salmon were not affected by the replacement of fish oil by vegetable oil. However, fatty acid composition of the flesh was affected. HUFA levels of fish fed vegetable oils were only 30% of those of fish fed fish oil. Linoleic and linolenic acid levels in fish fed vegetable oil increased by 5-fold and 20-fold, respectively when compared to those levels in fish fed fish oil. After being on the high fish oil finishing diet for six months, the HUFA levels in fish fed high vegetable oil diet were restored to 80% of those levels in fish fed high fish oil diet throughout the culture cycle.

3. Use of Alternative Feed Resources during a Full-life Cycle and Reducing Dioxins: Food Safety and Health by Dr. Marc H.G. Berntssen of National Institute of Nutrition and Seafood Research, Bergen, Norway (E-mail: marc.berntssen@nifes.no; website: www.nifes.no).

Dr. Berntssen reported the results of a trial in which Atlantic salmon were fed diets containing fish oil or vegetable oil throughout culture cycle (22 months). Levels of dioxins and dioxin-like PCBs were measured in the feeds and fish. Significant findings of the study were:

• The total concentration of dioxins and dioxin-like PCBs in fish (capelin) oil was 16.21 ng TEQ/kg whereas it was only 0.53 ng TEQ/kg in the vegetable oil.
• The level of dioxins and dioxin-like PCBs in fish followed that of the concentrations of the contaminants in the feed, but the levels of the contaminants in the flesh were lower than the corresponding feed concentration. Dilution due to growth explained why the flesh concentrations were lower than the feed concentrations.
• Assimilation efficiency of dioxin-like PCBs was higher than that of dioxins. Among dioxins, the more toxic dioxin-forms had a higher assimilation efficiency compared to the less toxic forms.
• While substitution of fish oil by vegetable oil resulted in 10-fold reduction of dioxins and dioxin-like PCBs, it also caused a 6-fold reduction in the n3/n6 ratio of the salmon fillet.

4. Removal of Dioxins and PCBs from Marine Oils: Current Status and Future Developments by Mr. Jan De Kock of De Smet Technologies & Services, Belgium (E-mail: Kok@DeSmetGroup.com; website: www.desmetgroup.com).

Providing a broad overview of major contaminants in fish oil (see box), Mr. De Kock presented options available for removal of the contaminants. A critical consideration in the removal of contaminants from fish oil is that the process should not remove beneficial components of the oil, particularly the HUFA. Mr. De Kock presented lab trials that showed that activated carbon treatment can effectively remove dioxins from marine oils up to 90%, but it is less effective in the removal of PCBs. The contaminants that persist after activated carbon treatment can be removed by stripping at low pressure (< 3 mbar) at 190C. Complete chemical refining is also highly effective in removing the contaminants (Table 1). The cost of treatment increases as the level of contaminants removal increases, and decreases with the increase in treatment capacity (Table 2).

Table 1. Effect of complete chemical refining on fish oil quality

Table 2. Treatment cost in Euros per ton of fish oil. The cost includes capital and operating costs.

5. Influence of Gene Modified Organisms as Feed Ingredients on Fish by Dr. Shuichi Satoh of the Tokyo University of Marine Science Technology, Japan (E-mail: ssatoh@s.kaiyodai.ac.jp).

Dr. Satoh presented the results of two trials conducted at his laboratory to understand whether foreign genes present in gene modified organisms (GMO) can be transmitted to fish that consume the GMO. In the first trial, guppy was used as the model fish. A test diet containing GMO soybean meal (SBM) and corn gluten meal (CGM) was fed to the fish for 24 weeks. The control diet contained non-GMO SBM and CGM. In the second trial, the diets were given to rainbow trout for 50 days, and afterwards the group receiving the GMO diet was switched to the control diet for another 28 days. The researchers checked for the presence of the foreign gene, Cauliflower Mosaic Virus 35s promoter (CaMV 35s promoter), in various tissues of the fish using PCR and in situ hybridization analyses. The findings showed that:

• The foreign gene was detected in the fish tissues indicating that the foreign gene could be transferred to the fish through ingredients.
• The rate of transfer of the foreign gene fragment was 30% in the guppy while it was only 10% in the trout.
• The foreign gene survived in the trout muscle only one week after the fish were switched to the control diet containing non-GMO ingredients.
• There was no effect of the GMO ingredients on fish growth.

Understanding PCBs, Dioxins and Related Contaminants

• "Dioxins" refers to several hundred, closely-related chemical compounds that belong to three closely related families: the chlorinated dibenzo-p-dioxins (CDDs), chlorinated dibenzofurans (CDFs) and certain polychlorinated biphenyls (PCBs). CDDs and CDFs are produced inadvertently by a number of human activities such as burning of wastes and fuels. Natural processes such as forest fires also produce CDDs and CDFs. PCBs are byproducts of industrial manufacturing, but manufacturing processes that produce PCBs have been banned in many countries.
• Dioxins are health hazards because they are carcinogenic.
• The most studied and one of the most toxic dioxins is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).
• Toxicity of dioxins and related compounds are expressed in Toxicity Equivalence (TEQ).
• TEQ of TCDD = 1.0. TEQ of other CDDs = 0.01-0.5. TEQ of CDFs = 0.1. TEQ of PCBs < 0.1 TEQ.
• European Union has placed regulatory limit on dioxins in feedstuffs, feed and food. Current upper limits are 1.25, 2.0, 2.25 and 4.0 ng TEQ/kg for fishmeal, refined fish oil, fish feed and fish, respectively. These limits are going to be reduced to 0.75, 1.5, 1.25 and 3 ng TEQ/kg, respectively in 2006. EU has not specified any limits on PCBs so far, but directives are expected in 2005.
• United States Food and Drug Administration (USFDA) has issued temporary tolerance limits for PCB residues in feedstuffs, feed and food. The limits are 2 ppm in feedstuffs of animal origin (including fish meal), 0.2 ppm in finished feeds and 2 ppm in the edible portion of fish and shellfish. USFDA has not set any limits on dioxin levels so far.