Results of the experiment on the nutritional value of native and non-native shrimps from the Baltic Sea and their importance as a food source for humans or in future fish farms

Around 100 species of macroinvertebrates live on or in the sediment of the Polish part of the Baltic Sea. They play important role for marine ecosystem and for human. Crustaceans and bivalves are prey for many marine fish and birds within their distribution area. For example, Saduria entomon and prawns from genus Palaemon are pray for cod. In many places in the world invertebrates are caught locally for human consumption (e.g. prawns or bivalves) and crustaceans are used as valuable live food source for aquaculture (e.g. prawns or amphipods). But not in Poland.
Beside energetic value of marine food the unique value is possession of long-chain poly-unsaturated fatty acids (LC-PUFAs). Some of them are called essential fatty acids (EFAs): ARA arachidonic acid (20:4ω6), EPA eicosapentaenoic acid (20:5ω3) and DHA docosahexaenoic acid (22:6ω3), because of their bioactive nature and the fact that presence of some fatty acids has a significant positive effect on animal growth. Marine organisms are main source of LC-PUFAs in human diet.
The aim of the case was to determine nutritional value of some invertebrates living in the Baltic Sea. Results of the study could help to choose species most valuable for aquaculture of invertebrates for using them in future as food for animals or human. What is more we compare results of nutritional value of non-indigenous prawn P. elegans with cultivated in RAS Penaeus vannamei.
In 2021 and 2022 invertebrates were sampled during cruises and in the coastal area of the Gulf of Gdańsk. Three species belonging to genus Palaemon, one isopod Saduria entomon, one amphipod Platorchestia platensis and mysis Neomysis integer as well as two bivalves: Mya arenaria and Rangia cuneata were collected. Samples were kept in freezer at temperature below -20°C and were prepared for further analysis. Length, mass of all individuals were determined. The invertebrates were measured (total length and wet mass). Then, the whole soft tissue from individual was freeze-dried and homogenized. Additionally, prawns P. vannamei cultured in laboratory in RAS in 2021 were compared with P. elegans from the Gulf of Gdańsk. For this purpose, abdomens of the prawns were separated, freeze-dried and homogenized. Carbon, nitrogen and lipids content as well as fatty acids composition were analyzed in prepared samples. In total 38 fatty acids were detected in studied invertebrates. Fatty acids that did not exceed 0.5% of total fatty acid in at least one invertebrate were excluded from our analysis. For this study we used 25 fatty acids which constituted from 97,9 to 99,2% of the total detected fatty acids. The fatty acids were divided into three groups: saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA).
Our results show that lipids content varies between 5% d.w. (dry mass) for isopod S. entomon to 12% d.w. for Baltic prawn P. adspersus. Abdomens of cultured P. vannamei had 57% higher content of lipids than abdomens of wild P. elegans (7% d.w.). Carbon content (46% d.w.) in abdomens of P. vannamei was slightly lower (2%) than in P.elegans but nitrogen content (14.3% d.w) was 6% higher.
For all studies invertebrates, a higher proportion of PUFA than that of MUFA and SFA were observed. The percentages of PUFA in the studied species varied from 27% in P. platensis to 50% in S. entomon. Content of EFAs varied from 15 to 40% in the mentioned species. Generallycrustanceans had high content of EPA (usually more than 15%) with one exception P. platensis with only 9%. Very high values of EPA were found for prawns from genus Palaemon (>20%). Especially high content of DHA (>10%) was found in N. integer, S. entomon and Palaemon macrodactylus. EFAs content in abdomens of P. vannamei was lower than in P. elegans, 29 and 32% respectively.
High content of essential fatty acids found in non-indigenous prawns P. elegans and P. macrodactylus show that they could be a valuable food for fish in aquaculture or for human. It is worth mentioning that especially P. elegans is easy to breed.

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