Exploring the Potential of Atlantic Mesopelagic Species Processed on Board Commercial Fishing Vessels as a Source of Dietary Lipids

Abstract

This study investigates the use of untapped mesopelagic species as a source of long-chain polyunsaturated omega-3 fatty acids (LC n-3 PUFAs) to meet the growing demand. The challenges faced by commercial fishing vessels, such as varying catch rates and species distribution affecting lipid levels, are addressed. Marine oils were produced post-catch using thermal separation and enzymatic hydrolysis during four commercial cruises, screening approximately 20,000 kg of mixed mesopelagic species. Maurolicus muelleri and Benthosema glaciale were the dominant species in the catch, while krill was the primary bycatch. The lipid composition varied, with B. glaciale having a higher prevalence of wax esters, while triacylglycerols and phospholipids were more predominant in the other species. LC n-3 PUFAs ranged from 19% to 44% of lipids, with an average EPA + DHA content of 202 mg/g of oil. Both processing methods achieved oil recoveries of over 90%. Estimates indicate that the mesopelagic biomass in the Northeast Atlantic could supply annual recommended levels of EPA + DHA to 1.5 million people, promoting healthy heart and brain functions. These findings offer valuable insights for considering mesopelagic species as a potential source of dietary marine lipids, laying the groundwork for further research and innovation in processing and obtaining valuable compounds from such species.

Keywords: Benthosema glaciale; DHA; EPA; Maurolicus muelleri; enzymes; hydrolysis; krill; marine oils; omega-3; thermal separation.

Figure 1

The map indicates the locations of the trawl hauls conducted during Cruises 1–4. The latitude on the y-axis and longitude on the x-axis indicate the geographical position of the hauls. Twelve hauls were conducted during Cruise 1 (shown in the map), but only samples from hauls 1–10 were used for the analysis and processing of the raw material (see Table 1).

Figure 2

Flow chart showing the experimental design for the on-board processing experiments. In the flow chart, thermal inactivation refers to thermal separation. This method was used as a processing procedure, but it was also used to inactivate the enzymes during hydrolysis. Reprinted with permission from BioRender.com [2024].

Figure 3

Principal component analysis (PCA) of the total lipid content, lipid classes, fatty acid profiles, and presence of mesopelagic species in the hauls. Eigenvalues in brackets represent the variance percentage explained by each axis (PC1 and PC2). The abbreviations for the lipid classes are as follows: WE: wax esters; FFA: free fatty acids; TG: triacylglycerols; Ch: cholesterol; PH: phospholipids. For the fatty acid profiles, the total sum of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), and total sum of LC n-3 PUFAs were included in the PCA analysis. The term “others” refers to the presence of species other than M. muelleri, B. glaciale, or krill in the catch. M. norvegica likely dominated among krill species, but taxonomic identification was not performed and all of the krill species that came aboard as bycatch are included here.

Figure 4

Graphical illustration of the provision of the dietary lipids EPA + DHA to the population from the mesopelagic biomass observed during Cruises 1–4, together with estimates of biomass in the Northeast Atlantic and globally. The units of measurement are represented by the letters M, G, and k, which correspond to million, giga, and kilo, in that order. Consequently, Mt, Gt, and kt refer to million tons, giga tons, and kilo tons, respectively. The arrows reflect the conversion from the biomass into an average content of EPA + DHA and the size of the population that would meet the yearly recommendations of 250 mg EPA + DHA. The dashed rectangles in green, pink, and red represent these outcomes under three different scenarios, according to oil recovery rates set at 27%, 90%, and 100%, respectively. These assumptions were made based on the lowest and highest oil recovery rates reported in Table 5, and a full recovery scenario. This means that the oil obtained from the biomass would represent 27% of the total lipid content, 90%, or the same amount as in the raw material. Based on this premise, an average content of 202 mg/g of oil (derived from Cruises 1–4) was used to calculate the average EPA + DHA provided by the three different biomasses and oil recovery rates. Reprinted with permission from BioRender.com [2024].