## 2 New Trends in Aquaculture Feed Production  
Fish plays a crucial role in global human nutrition as a source of essential nutrients [1,9]. Marine-derived ingredients (fishmeal and fish oil) are of critical importance in fish feed production [10]. Fishmeal primarily provides protein for fish growth but is also a valuable source of micro-nutrients such as vitamins, minerals, and lipids. In addition, fishmeal contributes to improved feed digestibility and palatability, particularly in weaning diets for many species [11]. Fish oil is used in fish feed to meet the requirements of the long-chain omega-3 series essential fatty acids (HUFAs, highly unsaturated fatty acids) [12] DHA (docosa-hexaenoic acid) and EPA (eicosapentaenoic acid) [13]. In recent decades, fish oil has been partially replaced with several vegetable oils, such as canola and flax oil [14]. The use of marine-derived ingredients (meal and oil) is higher in species of high commercial value, such as rainbow trout and Atlantic salmon [1,15]. In 2020, 15 MT of harvested fish was used for fishmeal and fish oil production [1]. Fishmeal and fish oil are obtained from small pelagic species (e.g., anchovies (_Engraulis encrasicolus_) and blue whiting (_Micromesisitus poutassou_)). The fisheries are primarily concentrated in certain countries, notably, Peru, Chile, Norway, and Thailand [16]. The amount of fish oil recovered for anchovies is approximately 5% of the total weight, while that for herring (_Clupea haregus_) and capelin (_Mallotus villosus_), the most commonly used fish for fish oil production in Europe, is approximately 10%. Up to 33% of fishmeal and fish oils are obtained by means of by-products. Fishmeal and fish oil are obtained through the same production process [17]. On average, processing one tonne of caught fish yields 225 kg of fishmeal and 50 kg of fish oil [18]. The processing coefficient varies according to the different fish species, sizes, and seasons of capture [19]. From 2000 to 2020, global fishmeal production decreased from 6.6 to 4.8 MT and fish oil production from approximately 1.5 to 1.0 MT. Over the past decade, fishmeal and fish oil prices have been higher than those of vegetable meals and oils (Table 8). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Year** & **Soybean Meal** & **Fishmeal** \\ \hline
2010 & 400 & 1600 \\
2012 & 410 & 1250 \\
2014 & 450 & 1610 \\
2016 & 390 & 1590 \\
2018 & 400 & 1600 \\
2020 & 380 & 1550 \\ \hline \hline \end{tabular} Source: FAO, 2022 [1].  
\end{table} 
Table 8: Soybean meal and fishmeal prices over the past decade (USD/t). From 2000 to 2020, in fish feed manufacturing, the fishmeal percentage increased from 33% to 69%. During the same period, the fish oil percentage increased from 55% to 75%. Recently, the increasing amounts of fish products used in fish feeds have raised global public concern regarding the sustainability of the marine system [1; 20]. Indeed, excessive fishing activity could result in a global reduction in the valuable ecosystem benefits of fish [10]. Moreover, a portion of the caught fish could be used for direct human consumption [5; 19; 21]. Although marine-derived resources continue to play an important role in fish feed production, the use of plant-derived ingredients is steadily increasing [22]. Some feed ingredients, such as grains and legumes used in pet food, present some critical issues for fish. In fact, fish are more sensitive to some substances, such as antinutritional factors and toxins. For this reason, additional processing steps are used in the production of fish feed to increase their nutritional value. There are several factors to consider when using new feed ingredients to replace fishmeal, including: nutritional value, availability and price, customer acceptability, and effects on growth and health [3]. Different types of plant-based ingredients have been studied. Soybean products are the most widely used plant-based protein source in trout feeds, used alone or in combination with other plant-based ingredients.