4. New food sources and food production systems

4.2 Jellyfish

Jellyfish are marine invertebrates that are abundant in both cold and warm ocean waters, along coastlines and in deeper waters. They belong to the phylum Cnidaria and are different from the cephalopods (squids, octopuses, cuttlefish), but closely related to corals and sea anemones (Boero, 2013).

Jellyfish aggregations are a natural feature of a healthy marine ecosystem (Griffin et al., 2019; Hays, Doyle and Houghton, 2018) with periodic fluctuations in their occurrence and abundance (Condon et al., 2013). While there is lack of data to show if the global jellyfish population is rising (Condon et al., 2013; Mills, 2001; Sanz-Martín et al., 2016), there is a general agreement that over the last few decades certain regions have observed a significant increase in the number and duration of jellyfish blooms⁶ (Boero, 2013; Brotz et al., 2012; Dong, Liu and Keesing, 2010). Around the world some of these blooms have been appearing beyond their traditional habitats.

Conditions brought by climate change – warming seas, ocean acidification – as well others such as increase in plankton numbers and oxygen depletion from eutrophication events can be conducive to these population increases and geographic expansions (Boero, 2013; Mills, 2001; Purcell, Uye and Lo, 2007). Overfishing removes top predators (red tuna, swordfish, sea turtles) and competitors allowing certain jellyfish populations to thrive (Boero, 2013; Purcell, Uye and Lo, 2007). Other factors that can potentially be linked to jellyfish blooms include introduction of non-native species of jellyfish by ships or ocean currents, and proliferation of man-made coastal structures (sea walls, oil rigs, docks, offshore windfarms and so on) which act as shaded habitats for jellyfish polyps⁷ (Boero, 2013; Purcell, Uye and Lo, 2007; Vodopivec, Peliz and Malej, 2017).

All over the world jellyfish blooms have been disastrous for the fishing and aquaculture industries by clogging nets and destroying fish farms (Bosch-Belmar et al., 2021; Dickie, 2018; Siggins, 2013; Tucker, 2010). They have forced temporary closures of power plants in Sweden and Israel (Kiger, 2013; Rinat, 2019) and a desalination plant in Oman (Vaidya, 2003) by blocking pipes that bring in seawater. Jellyfish blooms have also impacted coastal economies and public health by swarming popular tourist destinations (Tucker, 2010).

What is driving the recent interest in jellyfish consumption?

Flourishing jellyfish blooms create a vicious cycle where the jellyfish prey on fish eggs and larvae as well as compete for the same food source as the fish stock that are already affected by overfishing (Boero, 2013). Attempts to capture and remove jellyfish blooms, together with moving towards diversifying sustainable fishing to feed a growing global population may necessitate creating commercial markets for jellyfish across various global regions (EC, 2019; Petter, 2017; UN Nutrition; 2021; Youssef, Keller and Spence, 2019).

While eating jellyfish may strike many as unconventional, jellyfish have in fact been consumed in some places of Asia as part of the traditional cuisine for generations and are valued for their health benefits (Brotz, 2016). The edible species tend to be low in carbohydrates and lipids, high in protein (mainly represented by collagen) content and several minerals (De Domenico et al., 2019; Khong et al., 2016; Leone et al., 2015).

While some jellyfish species can be toxic to humans, there are others that are safe to consume (Brotz, 2016). Jellyfish fisheries can be found in a number of Asian countries such as Japan, Malaysia, Republic of Korea, and Thailand, with export industries also found in Australia, Argentina, Namibia, Bahrain, Nicaragua, Mexico and the United States of America, among others (Brotz, 2016; Brotz et al., 2017). Though the total marine capture of Rhopilema spp. and Stomolophus meleagris (cannonball jellyfish) was estimated at approximately 300 000 tons in 2018 (FAO, 2020), there is no reliable data on comprehensive catch statistics for jellyfish.

What are the food safety implications to be considered?

Like other foods, jellyfish are also associated with some food safety hazards which must be taken into consideration to drive further development in this sector.

Microbiological hazards

Fresh jellyfish tend to spoil readily at ambient temperatures and therefore they tend to be processed relatively quickly after capture. This reduces risks associated with microbiological contamination. According to studies, no foodborne pathogens have been found to be associated with jellyfish (Bonaccorsi et al., 2020; Raposo et al., 2018). However, research on the diversity of bacterial community associated with jellyfish show the presence of potentially pathogenic bacterial genera – Vibrio, Mycoplasma, Burkholderia and Acinetobacter, among others (Kramar et al., 2019; Peng et al., 2021). This denotes that jellyfish can serve as vectors of pathogenic bacteria implicated in affecting human health as well as the health of marine animals (Basso et al., 2019). In addition, Bleve et al. (2019) reported low level of Staphylococci in jellyfish and attributed that to the microbial content found in the specific marine environment where the jellyfish were collected.

Chemical hazards

Heavy metals: Bioaccumulation of pollutants from the marine environment is an issue of food safety concern in jellyfish. Epstein, Templeman and Kingsford (2016) studied the rate of uptake and retention of trace metals in Cassiopea maremetens and found that metal accumulation in jellyfish began within 24 hours of exposure to treated water. High concentrations of copper were observed, reaching more than 18 percent above ambient concentrations (Epstein, Templeman and Kingsford, 2016). Another study conducted by Muñoz-Vera, Castejón and García (2016) assessed the possibility of bioaccumulation of various trace and heavy metals (aluminium, titanium, chromium, manganese, iron, nickel, copper, zinc, arsenic, cadmium and lead) by Rhizostoma pulmo, in the Mediterranean coastal lagoon from southeast Spain. The bioconcentration of these elements in the jellyfish, in relation to seawater metal concentration, was high, especially arsenic (Muñoz-Vera, Castejón and García, 2016). This risk underscores the importance of carrying out constant monitoring of the water where jellyfish are captured or bred.

Algal toxins: A solitary case of suspected ciguatera poisoning after ingestion of imported jellyfish has been reported in published literature (Zlotnick et al., 1995). Further investigations (Cuypers et al., 2006; Cuypers et al., 2007) will be needed to explore this potential risk. No other reports of intoxication, from marine toxins, upon consumption of edible jellyfish was found in literature.

Allergenic potential: Research shows that people with history of allergic reactions to crustaceans, cephalopods and/or fish can safely eat jellyfish without any adverse reactions (Amaral et al., 2018; Raposo et al., 2018). Most allergic reactions to jellyfish consumption have been recorded in people who have been previously stung by the invertebrate (Imamura et al., 2013; Li et al., 2017). However, there are a few instances of anaphylaxis post jellyfish-ingestion recorded in individuals with no history of being stung by jellyfish (Okubo et al., 2015). The allergens in jellyfish that cause these allergic reactions upon consumption are yet to be identified.

Other chemical hazards from the post-harvest stage: A traditional way of processing jellyfish employs a brining solution containing alum.⁸ This process dehydrates the jellyfish and decreases the pH, and can extend the shelf-life if the jellyfish is kept at a suitable temperature post processing (Hsieh, Leong and Rudloe, 2001; Lin et al., 2016). There are concerns regarding the amount of aluminium retained in jellyfish products as a result of using alum (FAO and WHO, 2012; Lin et al., 2016). A study looking at dietary exposure to aluminium in China, Hong Kong SAR observed high levels of aluminium in ready-to-eat jellyfish and jellyfish-based products (Wong et al., 2010). Although maximum levels (MLs) have not been established at the level of the Codex Alimentarius, some Asian countries have set MLs for aluminium (100 mg/kg in dry weight), specifically for jellyfish. In addition, the Joint FAO/WHO Committee on Food Additives (JECFA) have determined a provisional tolerable weekly intake (PTWI) of 2 mg/kg body weight for aluminium, with estimates of dietary exposure to aluminium (not including jellyfish, in most countries) known to potentially exceed the PTWI (FAO and WHO, 2011).

A jellyfish bloom.
©Shutterstock/Ethan Daniels

High levels of dietary aluminium have been suggested to play a role in developmental problems in infants and young children as well as liver damage, reproductive toxicity, inflammatory bowel disease (IBD), and potential risk for developing Alzheimer’s disease in adults (de Chambrun et al., 2014; FAO and WHO, 2006; FAO and WHO, 2011; Lin et al., 2016; Tomljenovic, 2011; Yokel, 2020).

Physical hazards

Jellyfish, like other marine organisms, have been reported to ingest plastics (macro, micro and nano) from their environment, facilitating their transfer up the trophic level and potentially posing as physical hazards (Costa et al., 2020; Iliff et al., 2020, Macali and Bergami, 2020; Macali et al., 2018; Sun et al., 2017). While the implications of microplastics on human health is still not well understood (Chapter 6), any potential risk of human exposure to microplastics through jellyfish consumption will need to be explored through further studies.

What is the way forward?

Consumption of edible jellyfish is not prevalent in Western countries due to the lack of market demand for jellyfish products as well as the absence of adequate processing methods and lack of national safety and quality standards. Research on alternative processing techniques to eliminate alum, for instance, by using high-temperature treatment, can open up potential markets (Leone et al., 2019). In addition, thorough assessment of food safety hazards associated with jellyfish harvesting, processing and consumption will help to establish appropriate hygiene and manufacturing practices as well as develop relevant regulatory frameworks for the sector.

While it may be tempting to exploit this marine resource as food, it is important to note that jellyfish populations can be extremely variable in their abundance from year to year, which can make investments in infrastructure to create new fisheries quite challenging. Few jellyfish species are edible, and therefore not all blooms can be managed by fishing them. In addition, only a small subset of jellyfish species form blooms. Focusing on a few species may not be environmentally sustainable as it increases the chances of overfishing them unless proper management strategies are put in place. For instance, commercially important Rhopilema esculentum is subjected to stock enhancement in China where juvenile jellyfish are reared and released in Liaodong Bay of Bohai Sea (Dong et al., 2009; Dong et al., 2014). This is in response to natural fluctuations in their population as well as overfishing. Furthermore, it is essential to promote jellyfish research (Gibbons and Richardson, 2013) by an ecosystem-based approach to advance knowledge and predictive modelling of jellyfish blooms as well as to implement strategic monitoring and management plans to develop this resource as a sustainable food source