International Journal of Aquaculture, 2024, Vol.14, No.1, 40-50 http://www.aquapublisher.com/index.php/ija 45 6 Case Study 6.1 Detailed analysis of a specific case of aquaculture fish with enhanced fatty acid composition In this case study, we focus on the Atlantic salmon (Salmo salar), a species that has been extensively studied for its fatty acid composition, particularly the levels of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) (Figure 1), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The replacement of traditional fish oil and fishmeal with plant-based ingredients in the diet of farmed Atlantic salmon has led to a reduction in these essential fatty acids in their fillets (Sprague et al., 2016; Tocher et al., 2019). However, selective breeding and dietary modifications have been explored to enhance the n-3 LC-PUFA content in farmed salmon (Horn et al., 2018). Figure 1 Relationship between fish body weight and proportional content of fatty acids in the muscle (Adopted from Horn et al., 2018) Based on the data in the figure by Horn et al. (2018), the relationship between fish body weight and the proportional content of different fatty acids in the muscle can be summarized as follows: As the fish body weight increases, the content of 16:0 (palmitic acid) remains stable, while the content of 18-carbon fatty acids (such as 18:1n-9 and 18:2n-6) shows an upward trend. However, the proportions of EPA (20:5n-3) and DHA (22:6n-3), which are n-3 polyunsaturated fatty acids, decrease with increasing fish body weight. This indicates that during fish growth, the accumulation and utilization of different types of fatty acids in the muscle vary, with a particularly higher utilization of n-3 polyunsaturated fatty acids. All estimates have been adjusted for body weight, ensuring the accuracy and comparability of the data. 6.2 Analysis of the impact of feed formulation changes on the fatty acid composition of atlantic salmon This approach combines dietary intervention and genetic selection. Researchers compared the fatty acid composition of over 3,000 farmed Scottish Atlantic salmon from 2006 to 2015, analyzing the impact of changes in feed formulations on the fatty acid composition of the salmon (Figure 2). Additionally, genetic parameters for muscle content of individual fatty acids were estimated to evaluate the potential for selective breeding to increase n-3 LC-PUFA levels in salmon tissues (Horn et al., 2018). The dietary interventions included the use of microalgae and genetically modified crops as alternative sources of EPA and DHA (Sprague et al., 2016; Tocher et al., 2019).
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