A thorough screening of publication lists obtained from three bibliographic databases (i.e. PubMed, Web of Science, and Google Scholar) was conducted. The Google Scholar database was processed with the use of the platform provided by Harzing (2007) (Harzing, 2007) to overstep limitation in Boolean search tools and importable items. The last search date for Google Scholar was October 2020, while for the other databases, it was March 2023.

The search queries in each database utilized the same keywords (“jellyfish” “scyphozoa”, “schyphomedusa, “nutrient” “microelement” “macroelement”, “vitamin”, “protein”, “lipid*”, “ash”, “organic matter”, “carbohydrate”, “amino acid”, “fatty acid”, “elemental”, “biochemical”, “nutritional”, “gross” “proximate”, composition”, “compound”) and were expressed in the appropriate language of the specific database ( Supplementary File 1 ).

To manage the large number of items, a three-step eligibility criteria process was implemented ( Figure 1 ). Firstly, titles were screened for relevance to the paper’s objective or the potential to report nutritional data. Secondly, structured eligibility criteria were applied to define the nutritional composition of jellyfish, excluding publications reporting data on specific substrates like collagen or gelatin and considering only papers focusing on the medusa stage of the Scyphozoa class. Thirdly, only scientific publications with available data in English were considered. Briefly, only data related to wild organisms, whole body, oral arms, bell, and raw material were included, while entirely reared and processed organisms, other body parts such as mesoglea and gonads, and extraction substrates such as collagen and gelatin were excluded. However, aspects influencing nutritional composition and potential use as feed components were discussed in the text.

Qualitative parameters included in the final tables were family, species, and body parts. Data related to factors not evaluated in the eligibility criteria process, such as site, size, and sex, were extracted as a range or mean if directly available in the reference. Nutritional composition data, if only graphically presented were extracted with an online software WebPlotDigitizer (Rohatgi, 2017).

Data were categorized into four main groups: proximate composition (Pc), amino acids (AA), fatty acids (FA), and minerals (Mi). Each nutritional compound was converted into a unique unit of measurement, applying appropriate unit conversions ( Supplementary File 1 ). Water content data, if missing, was back-calculated from the respective specular dry weight values reported in the references.

Furthermore, nutritional composition data for the most used aquafeed ingredients and supplements were extracted from the NRC (Nutrient Requirements of Fish and Shrimp, 2011) (NRC, 2011) and other sources as needed. Data were unit-converted for direct comparison with the jellyfish nutritional profile.

Jellyfish, characterized by their high moisture and consistent ash content, generally exhibit lower protein content (DW) compared to established feed ingredients like fish meal and soybean meal ( Figure 3 ). However, their protein content is comparable to seaweed (14.4 ± 6.6% DW) and to other plant-based sources such as corn (10.6 ± 1.3% DW), and wheat (15.6 ± 2.5% DW). Certain species, such as Rhopilema esculentum and Rhopilema hispidum (oral arms) display protein content within the range of soya bean meal ( Figure 3 ).

Considering the quality of proteins in terms of essential amino acids (EAA), jellyfish present a heterogeneous profile ( Supplementary File 2 ), with lower relative amounts of EAA compared to traditional protein sources like fish meal and soyabean meal ( Figure 4 ). Moreover, jellyfish demonstrate a variable quantitative EAA profile across species (Semaestomae generally displaying lower amino acid levels compared to Rhizostomae) and body parts, with oral arms consistently exhibiting higher EAA values compared to bell segments ( Supplementary File 2 ). Notably, certain species like Acromitus hardenbergi (0.57-14.8% DW), Rhopilema esculentum (0.29-7.96% DW), and Rhopilema hispidum (0.06-9.8% DW) display particularly high net quantitative EAA profiles. Along with non-EAAs as glycine, proline, hydroxyproline, aspartic acid, glutamic acid and alanine also arginine resulted consistent in jellyfish ( Supplementary File  2 ).

Amino acid composition, expressed as % of total amino acid (%TAA), is relatively consistent among species ( Tables 2 , 3 ). Under this perspective, jellyfish have similar or higher proportions of EAA (42.6- 48.1%TAA in Semaeostomeae and 49.2-54.1%TAA in Rhizostomeae) compared to fishmeal (43.4%TAA), soybean meal (46.0%TAA) or seaweed (45.7%TAA) (Angell et al., 2016). Moreover, the proportion of limiting amino acids in jellyfish demonstrates comparability to commonly used and alternative protein sources such as fish meal, soybean meal, and seaweed. Methionine levels in jellyfish (1.5- 1.9% TAA) fall within the range observed for seaweed (1.25% TAA) and fish meal (2.8% TAA) and the proportion of lysine in jellyfish (6.4-12.2% TAA) also appears to be higher or comparable to the one observed in soybean meal (6.66% TAA), seaweed (5.88% TAA), and fish meal (7.4% TAA) (Angell et al., 2016).

The overall lipid content (% DW) of jellyfish is low, varying between 0.2 and 5.8, and comparable to some plant-based ingredients ( Figure 3 ). Nevertheless, some species such as Cotylorhiza tuberculata, (12.3% DW) Cyanea nozakii, (8.1% DW) and Stygiomedusa gigantea (10.2% DW) display lipid values similar or even higher than those found in fish meal (9.58 ± 1.16) ( Figure 3 ).

In terms of fatty acid composition, saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA), particularly arachidonic acid (ARA) (2.8-23.7), eicosapentaenoic acid (EPA) (1.23-25.9), and docosahexaenoic acid (DHA) (0.8-25.9), were more abundant than monounsaturated fatty acids (MUFA) ( Supplementary File 2 ). However, high variability was observed among species, with some species like Aurelia aurita and Pelagia noctiluca, presenting consistently low levels of these compounds ( Supplementary File 2 ).

Despite the similarities between jellyfish and fish oil fatty acid profiles, the ω3/ω6 ratio is higher in fish oil (12.4- 24,1% DW) (NRC, 2011) due to the greater amount of ARA in jellyfish ( Figure 5 ).

Macroelements, including sodium (Na) (37.4-80.79 g/kg DW), potassium (K) (1.26 – 2.29 g/kg DW), calcium (Ca) (1.33 -2.36 g/kg DW), magnesium (Mg) (4.27 – 6.92 g/kg DW), phosphorus (P) (0.046 – 59.55 g/kg DW), and chlorine (Cl) (326-587.6 g/kg DW), are abundant in jellyfish, with variations observed among species and body parts and lower concentrations reported for Pellagia noctiluca ( Supplementary File 2 ). Rizhostoma species generally exhibit higher concentrations of K (5.57-126.70 g/kg DW) compared to Sematostoma species (1.6-19.66 g/kg DW). Compared to fish meal, jellyfish exhibit lower Ca content, but comparable levels to seaweed ( Supplementary File 1 ). Regarding P, its content in jellyfish is variable, but generally comparable to other ingredients used in aquafeeds ( Supplementary File 1 ).

Microelements in jellyfish display more variability, with variable concentrations for iron (Fe) (0.59- 252 mg/kg DW), copper (Cu) (0.11 – 49.82 mg/kg DW), zinc (Zn) (3.61 – 400 mg/kg DW), manganese (Mn) (0.11 – 18.66 mg/kg DW) and selenium (Se) (0.31-5.49 mg/kg DW) content ( Supplementary File 2 ). No data on iodine (I) were encountered. Zn concentrations, especially in species associated with symbiotic dinoflagellates, namely - Cotylorhiza tuberculata (Furla et al., 2011; Enrique-Navarro et al., 2022) and Cassiopea sp (Templeman and Kingsford, 2010; Templeman et al., 2021), - show potential for fish nutrition.

Collagen is a prominent protein constituent of jellyfish that in some species accounts for about 50% of its total protein content (Merquiol et al., 2019). Given the high content of glycine, proline, and hydroxyproline in collagen, it was not surprising to find these amino acids abundant in jellyfish ( Supplementary File 2 ). Proline and hydroxyproline are conditionally EAA whose dietary intake might become necessary under specific conditions like rapid growth, illness, or deficiencies in other nutrients (Li and Wu, 2018) and consequently represent an attractive characteristic of jellyfish for aquatic animal nutrition. Glycine, as one of the major non-EAA in jellyfish may play a role in gut health and immune function in fish (Hoseini et al., 2022; Aidee et al., 2023). In terms of amino acid composition, jellyfish contain high proportions of specific amino acids comparable to or higher than those found in commonly used protein sources. The consistent proportion of lysine and arginine ( Table 2 ) unravel appealing characteristics accounting that their requirements for fish and crustaceans are among the highest in the comparison with other EAA (Xing et al., 2024). Therefore, limitations associated with plant-based feedstuffs, particularly regarding AA balance deficiencies (Cai et al., 2022), could be effectively supplemented by incorporating conditionally EAA and/or EAA from selected jellyfish species/parts, namely R. esculentum and R. hispidum arms, and A. hardenbergi. However, accounting the net amount of protein, jellyfish emerge as a more suitable feed ingredient to fulfil the protein requirements of freshwater fish, as marine species typically require higher levels of dietary proteins (40–55%) compared to most freshwater fish (25–40%) (Velasco Santamaría and Corredor Santamaría, 2011; Bowyer et al., 2013). Moreover, despite jellyfish possessing promising protein content, processing methods can significantly impact the bioavailability and digestibility of jellyfish protein. Studies on mammals have shown that hydrolyzed collagen (gelatin) can decrease food efficiency and protein bioavailability (Bordin and Naves, 2015). This finding highlights the importance of investigating processing techniques specific for jellyfish to optimize their nutritional value as an aquafeed ingredient. Beyond its nutritional merits, jellyfish collagen, peptides and free amino acids exhibit a plethora of bioactive functionalities to be dealt with further ahead.

ARA represents the jellyfish characteristic fatty acid. Studies suggest that ARA may play a significant role in growth performance, reproduction, survival, and stress resistance in marine organisms (Xu et al., 2010; Torrecillas et al., 2017, 2018; Ding et al., 2018). However, excessive ARA intake can lead to issues such as reduced performance in Litopenaeus vannamei (Araújo et al., 2020) and problems as at metamorphosis in flatfish (NRC, 2011). Jellyfish could serve as a natural source of ARA to enrich diets according to experimental evidence. Takifugu rubripes, tiger puffer, fed with Aurelia sp. showed increased proportions of polar lipids, ω −3 and ω −6 highly unsaturated fatty acids, especially ARA and DHA (Miyajima-Taga et al., 2017a). Similarly, threadsail filefish (Stephanolepis cirrhifer) fed artificial diet supplemented with N. nomurai presented high levels of ARA (Miyajima-Taga et al., 2015, Miyajima-Taga et al., 2017a). Jellyfish could be used to supplement terrestrial plant oils as lipid source, mitigating their commonly reported deficiencies in long chain PUFA (Zhang et al., 2024). Despite the generally low lipid content in jellyfish, certain species with higher lipid levels—such as Cotylorhiza tuberculata, Cyanea nozakii, and Stygiomedusa gigantea—could serve as a notable lipid source with an attractive fatty acid profile. Additionally, reared jellyfish have been reported to exhibit significantly higher lipid content (De Domenico et al., 2025) and elevated levels of SFA and PUFA, alongside lower MUFA levels (Wang et al., 2021b), compared to their wild counterparts. These findings suggest the potential for jellyfish to be utilized as a lipid source, though further research is required to optimize such practices.

Mineral nutrition in fish, though less studied than other nutrients (Lall and Kaushik, 2021), is essential for their growth and health (NRC, 2011). In jellyfish differences in macro element concentrations between body parts suggest influence from osmotic balance and floating capacity (Costa et al., 2019).

Microelements are typically more limited than macro element in compound feeds and dietary supplementation of trace minerals is commonly employed to ensure optimal growth and health of cultured species (Watanabe et al., 1997). Jellyfish could serve as a potential future source of minerals for dietary supplementation. However, attention must be paid to possible pollution by toxic trace elements (Muñoz-Vera et al., 2015, Muñoz-Vera et al., 2016; Templeman et al., 2021), particularly aluminium (Al) previously detected in the jellyfish, Catostylus tagi (Morais et al., 2009). Monitoring of toxic trace element levels in jellyfish is essential to ensure their safety for use in feed and food. Nevertheless, despite the potential anthropogenic impacts, jellyfish generally exhibit low levels of toxic elements, suggesting their suitability for consumption within regulatory limits. For instance, toxic elements (arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg)) concentrations in Rhizostoma pulmo were found below the limit levels for human consumption allowed by Australian, USA, and EU Food Regulations (Basso et al., 2021).

The composition of jellyfish biomass can vary due to several factors beyond body parts and taxonomy. For instance, size and water content (Malej et al., 1993; Lucas, 1994) affect protein content. In Aurelia aurita (Lucas, 1994) and Pelagia noctiluca (Malej et al., 1993), larger organisms show decreased protein content, likely due to egg transfer and organic content loss. Contrastingly, according to Schaub et al., 2023, Aurelia labiata shows increased protein with bell diameter, though larger diameter ranges indicate an opposite trend (Luskow et al., 2022). These variations suggest complex interactions beyond size, such as diet and trophic factors (Schaub et al., 2023). Seasonal shifts in diet and life cycle are the primary sources of nutritional variability. Although, size-based dietary shifts significantly influence lipid and fatty acid composition in Aurelia labiata (Schaub et al., 2023), the absence of size-based influence on lipid and fatty acid composition in Nemopilema nomurai confirmed the need to account for species-specific trophic habits (Wang et al., 2022a). Notable trophic transitions include shifts from grazing to detritus (Fukuda and Naganuma, 2001), from microzooplankton to microplankton and resuspended particles (Javidpour et al., 2016), and from seston to zooplankton diets (Wang et al., 2020). Pelagia noctiluca’s generalist trophic habits (Milisenda et al., 2018) further underscore the plasticity of jellyfish trophic interactions. Lipid composition varies with life stages, especially reproductive tissues. Gonads maintain consistent nutritional content, affecting overall organism composition during reproduction as indicated by energetic measurements (Doyle et al., 2007), direct lipid (Milisenda et al., 2014) and fatty acid content (Milisenda et al., 2018; Stenvers et al., 2020).

Although, gonadal lipid content has a crucial role as reserve during sexual maturation (Stenvers et al., 2020), food sources, nutritional status, and energy costs were further underlined to be the source of variation in FA profiles between wild and farmed Rhopilema esculentum. Specifically, farmed specimens were characterized by high level of SFA and PUFA and the lowest level of MUFA probably mirroring the adequate supply of specific diet in farmed specimens (Wang et al., 2021b). Macroelement composition in jellyfish reflects seawater composition (De Barba et al., 2016) but varies with species, body parts, and ecological factors (Costa et al., 2019). Microelement distribution has been studied in Cotylorhiza tuberculata (Muñoz-Vera et al., 2015) Rhizostoma pulmo (Muñoz-Vera et al., 2016) and Cassiopea sp (Templeman and Kingsford, 2010) suggesting that the variability in concentrations has a close relationship with water quality at the collection site. Zn and As concentration related with animal size in Cotylorhiza tuberculate and species-specific Zn level were mainly associated to symbiotic dinoflagellates living in Cotylorhiza tuberculata (Furla et al., 2011; Enrique-Navarro et al., 2022) and Cassiopea sp (Templeman and Kingsford, 2010; Templeman et al., 2021). Furthermore, for those jellyfish that harbor symbiotic photosynthetic dinoflagellates (zooxanthellate jellyfish), the strength of this association can be influenced by the life stage and geographic location of the jellyfish species (Djeghri et al., 2019). This variation in the symbiotic relationship ultimately affects the overall chemical composition of the jellyfish. Also, methodological factors like different drying methods may affect nutritional assessment (Siddiqui et al., 2024), impacting in the overall chemical composition (Fukushi et al., 2005; Emadodin et al., 2020), including amino acid content (Kogovšek et al., 2014; Yuferova, 2015; Leone et al., 2019).

Research and innovation in aquafeed formulation continue to explore diverse sources of bioactive compounds to optimize feed efficiency, promote animal health, and minimize environmental impact in aquaculture operations. Presently, the most promising sources of functioning feed additives are plant based, yeasts, mushrooms, seaweed, and their derivatives (Van Doan et al., 2019; Agboola et al., 2021; Firmino et al., 2021), besides the traditional sources such as fish discards and processing byproducts (Ozogul et al., 2021), and synthetic and semi-synthetic compounds (Wang and Hui, 2021).

However, multiple studies have demonstrated that extracts, collagens, and hydrolysates derived from various jellyfish species exhibit a range of potentially beneficial properties for aquaculture. Research suggests these products, particularly from species like Catostylus tagi (Morais et al., 2009) and Rhopilema nomadica (Leone et al., 2015, 2019), possess antioxidant activity, potentially helping to reduce oxidative stress and improve the overall health of organisms, and additionally prolonging shelf life of feeds. Extracts from Rhopilema tetrapilema (Esparza-Espinoza et al., 2023) have also shown antimutagenic properties, which could be beneficial for cell health. Other studies on Rhopilema esculentum suggest potential anti-fatigue effects (Ding et al., 2011), which could benefit aquaculture animals by reducing stress and improving their resilience. Additionally, extracts from Stomolophus nomurai demonstrate immunostimulant activity (Sugahara et al., 2006), with potential to boost the immune system of organisms.

Moreover, the presence of free amino acids in jellyfish ( Tables 4 , 5 ), including taurine, hydroxyproline, glycine, arginine, glutamic acid, and alanine, holds significant potential for enhancing the nutritional performance of farmed animals by stimulating feeding in various marine and freshwater fish (Kasumyan and Doving, 2003) and in shrimps (Tantikitti, 2014). Taurine has been shown to enhance growth performance and feed efficiency when supplemented in low-fish meal diets (Magalhães et al., 2019; Sampath et al., 2020). Therefore, jellyfish, rich in taurine, a prominent free amino acid in Aurelia sp., Aurelia aurita, and Nemopilema nomurai, present a promising source for this amino acid supplementation in aquafeeds.

Observations of several fish species attracted to jellyfish carcasses as bait (Sweetman et al., 2014; Dunlop et al., 2018) and to jellyfish portions in controlled feeding experiments, particularly with A. aurita (Miyajima et al., 2011b) and N. nomurai (Miyajima-Taga et al., 2015), also suggest that jellyfish possess unique characteristics that could make them valuable attractants for aquaculture feeds. This approach presents a sustainable alternative for enhancing the palatability of current feed trends that incorporate reduced levels of fish meal (Yue et al., 2022) as opposed to traditional fish derived attractants (He et al., 2022).

Fishery by-catches, including jellyfish may cause problems of waste management and disposal, and are costly (Coppola et al., 2021; D’Ambra and Merquiol, 2022). The multi-valorization of marine discarded wastes into high value-added materials approach helps to overcome these major issues, subsequently contributing to the reduction of marine environmental polluting discard accumulation in coastal areas (Govindharaj et al., 2019).

To conduct a meaningful evaluation of a new ingredient for feed purposes, we have not only characterized its nutritional aspects but also assessed the variability in composition, source, and species of origin, which constitutes a crucial element and essential step (Glencross et al., 2007).

According to the biochemical characterization in this review, jellyfish represent a valuable but complex resource for feed applications, offering nutritional variability and bioactive functionalities that can be harnessed to improve aquaculture sustainability and performance. The most relevant jellyfish properties, previously discussed, that are crucial for effective feed formulation and maximizing their potential as underutilized marine resources are as follows:

On the other hand, there are still challenges that need to be addressed if jellyfish are to be used as an aquafeed ingredient:

Despite the promising findings, further research and innovation are necessary to overcome limitations. Moreover, the safe utilization of jellyfish in both feed and food applications requires a thorough risk assessment, as outlined by Bonaccorsi et al. (2020), and strict adherence to established safety parameters, like any new aquafeed ingredient (Bleve et al., 2019).

Finally, assessing the long-term sustainability of utilizing jellyfish as an aquafeed ingredient is crucial. While this study positioned jellyfish as a potential alternative to currently limited feed ingredients, a dedicated sustainability assessment is needed. This analysis should consider factors such as harvesting practices and potential ecological impacts in the case of sustainable fishery exploitation (as recommended by Edelist et al., 2021) or take the shape of a comparative environmental assessment between a valorization process to produce a feed ingredient and different waste management options such as, composting, incineration and landfilling for a waste disposal scenario (Lopes et al., 2015) following jellyfish blooms.

The nutritional variability and bioactive functionalities of jellyfish underscore their potential as a feed supplement for aquaculture feeds rather than a novel major feed ingredient. Conditionally essential amino acids (glycine, proline, glutamic acid and taurine) proportion of EEA (lysine and methionine), the long chain fatty acid ARA and selected minerals such as Na, K, Cl, Mg, and Zn were highlighted in this study as a most promising source of supplementing ingredients.

Continued research and development efforts are needed to elucidate the full potential of jellyfish in feed applications, optimize processing techniques, and evaluate their impact on animal growth, health, and product quality. By associating jellyfish species from specific geographic regions to their applications in situ by the feed industry, this study may additionally contribute to the development and sustainability of jellyfish fisheries.