[[00 Home|English]] · [[00 首页|中文]] · [[ESCC as a thorny cancer/40 Diatom frustules/trash-fish|EN]] · [[刺乎乎的食管鳞癌/40 水中硅刺/trash-fish|中文]] # Trash fish ## Why we suspect trash fish We first highlight the importance of focusing on the "small" traits of trash fish: - small-bodied filter-feeding pelagic species → feed on algae including diatoms → diatom silica frustules accumulate in their guts - small-sized fish traditionally eaten whole → micronutrients are fully retained, while diatom silica frustules enter human diets - small-scale fisherfolk widespread across low- and middle-income countries in Africa and Asia → supply local communities with affordable, nutrient-dense trash fish Trash fish account for more than 30% of the total weight of global capture fisheries landings. ([https://meetings.pices.int/meetings/international/2022/pelagic/scope](https://meetings.pices.int/meetings/international/2022/pelagic/scope)). Most trash fish are processed as animal feed worldwide. However, in many parts of Africa and Asia, low-income populations rely on trash fish as a staple food, which plays a vital role in nutrition supply and food security [Robinson2025_PNAS.pdf](https://www.dropbox.com/scl/fi/0t0u0p57y4jiejkf7l1dc/Robinson2025.pdf?rlkey=r5cam1oo3tt5ctgv24cztsgbf&st=t6442ql4&dl=0) [FAO_Bavinck2023.pdf](https://www.dropbox.com/scl/fi/xmk4s8ep1o9lfkhcxj0uz/FAO_Bavinck2023.pdf?rlkey=tr3jtkojrg6e2o3ovmlk57n74&st=n85vv6hl&dl=0) [Robinson2022_NatFood.pdf](https://www.dropbox.com/scl/fi/iyp9wp67i8oxuey7oc1z1/Robinson2022_NatFood.pdf?rlkey=tpt2pgifv99ow3zsocrmao4hh&st=4y68v2bv&dl=0). ![[dagaa.png|w2/3]] _Fig. 1 Dried trash fish (locally named "dagaa") sold at local markets in Tanzania_ --- ## How we suspect trash fish Trash fish undoubtedly contributes to nutrition and food security, yet the food safety risks posed by abundant needle-shaped diatom silica frustules in these fish have long been overlooked. Three observations guide our hypothesis: - Not all regions consuming trash fish have high esophageal cancer (EC) risks - Not all productive trash fish openwaters have needle-shaped diatoms as predominant species in the phytoplankton community - Not all regions in the globe have the dietary culture of trash fish on the dining table We suspect that the unfortunate combination of **waters with prevalent acicular diatoms** and **tradition of eating trash fish** might be linking to esophageal cancer regional epidemics. --- ## Trash fish in Africa Dried small fish have been recognized by media as a "hidden superfood" vital for millions of poor households across Africa: https://www.nutritioninsight.com/news/africa-diet-malnutrition-dried-fish-superfood.html. > Kolding, J., van Zwieten, P., Marttin, F., Funge-Smith, S., & Poulain, F. 2019. Freshwater small pelagic fish and fisheries in major African lakes and reservoirs in relation to food security and nutrition. FAO Fisheries and Aquaculture Technical Paper No. 642. Rome, FAO. 124 pp. Licence: CC BY-NC-SA 3.0 IGO. | PDF | [FAO_Kolding2019.pdf](https://www.dropbox.com/scl/fi/cevr1qjh0i1e73selb2ff/FAO_Kolding2019.pdf?rlkey=caz6lh5bd3ams00yvttb0wq9p&st=ea1db3f3&dl=0) The FAO report shows that small pelagic fish species, naturally occurring or introduced to lakes and reservoirs, form some of the most important inland fisheries in Africa and account for the highest volume of inland fishery catches on the continent. > Robinson, J. P., O'meara, L., Fiorella, K. J., Byrd, K. A., Kjellevold, M., Ansong, R. S., ... & Hicks, C. C. (2025). Dried fish provide widespread access to critical nutrients across Africa. _Proceedings of the National Academy of Sciences_, 122(39), e2426844122. | PDF | [Robinson2025_PNAS.pdf](https://www.dropbox.com/scl/fi/0t0u0p57y4jiejkf7l1dc/Robinson2025.pdf?rlkey=r5cam1oo3tt5ctgv24cztsgbf&st=t6442ql4&dl=0) Robinson et al. analyzed sun-dried and smoked small fish from East and West Africa: 1. Dried small trash fish can largely meet the daily nutrient requirements of children and women. 2. One-third of local households consume dried trash fish every week. 3. Trash fish consumption is prevalent across both West and East Africa, while the two regions show striking differences in esophageal cancer incidence. Are there any differences in diatom species and morphology in trash fish between West and East Africa? Openwater habitats are particularly important for trash fish supply. **West Africa's coastal upwellings** and **East Africa's Great Lakes** support productive populations of small pelagic fishes. ![[East_Africa_Lake.png]] _Fig. 2 East African Rift Valley Lakes. Map source: Karp et al., 2012. [https://doi.org/10.1306/13291394M952903](https://doi.org/10.1306/13291394M952903)_ Phytoplankton surveys show that East African Great Lakes host a unique plankton community: low abundance of green algae, but rich in **long, thin diatoms (mainly Nitzschia and Fragilaria)**, filamentous cyanobacteria, picocyanobacteria and cryptophytes. - Hecky, R. E., & Kilham, P. (1973). Diatoms in alkaline, saline lakes: ecology and geochemical implications. _Limnology and Oceanography_, 18(1), 53-71. - Abo-Taleb, H. A., El-Tabakh, M. A., & Hendy, D. M. (2023). Plankton and fish nutrition in African lakes. In _Lakes of Africa_ (pp. 139-172). Elsevier. - Lung'Ayia, H. B., M'harzi, A., Tackx, M., Gichuki, J., & Symoens, J. J. (2000). Phytoplankton community structure and environment in the Kenyan waters of Lake Victoria. _Freshwater Biology_, 43(4), 529-543. - Descy, J. P., Hardy, M. A., Stenuite, S., Pirlot, S., Leporcq, B., Kimirei, I. & Sinyenza, D. (2005). Phytoplankton pigments and community composition in Lake Tanganyika. _Freshwater Biology_, 50(4), 668-684. - Hecky, R. E., and H. J. Kling. Phytoplankton ecology of the great lakes in the rift valleys of Central Africa. _Arch. Hydrobiol. Beih. Ergebn. Limnol_ 25 (1987): 197-228. By contrast, phytoplankton communities in West African coastal waters differ greatly. Existing studies indicate local diatoms are mostly blunt and round-shaped species; elongated or needle-shaped diatoms are not dominant here; or diatoms as a whole account for a small proportion of total algae. - Seu-Anoï, N. M., Ouattara, A., Koné, Y. J., & Gourène, G. (2011). Seasonal distribution of phytoplankton in the Aby lagoon system, Ivory Coast, West Africa. _African Journal of Aquatic Science_, 36(3), 321-330. - Emmanuel, B. E., & Onyema, I. C. (2007). The plankton and fishes of a tropical creek in south-western Nigeria. _Turkish Journal of Fisheries and Aquatic Sciences_, 7(2), 105-113. --- ## Trash fish in Asia Similar to Africa, some Asian countries with high EC incidence (e.g., Bangladesh) rely heavily on small and dried fish for food security and economic development. In China, while most other coastal provinces use their trash fish for animal feed, it is only the esophageal cancer epidemic areas of coastal southern China that value trash fish as human food. This geographic contrast in the human consumption of trash fish was disclosed in a report by Greenpeace East Asia which is concerned about the smaller mesh sizes of fishing nets and sustainable fishery. ![[TrashFishDestination_China.png]] _Fig. 3 Map showing esophageal cancer mortality rates and trash fish utilization across coastal provinces of China. Right map adapted from: Greenpeace, 2017. [Greenpeace2017.pdf](https://www.dropbox.com/scl/fi/ov60e7mp82jfvzp0vdd2x/Greenpeace2017.pdf?rlkey=po38pf2i43cy6xo1nut3k08pi&st=itf66a0s&dl=0)_ --- ## Trash fish in South America In South America, high esophageal cancer incidence concentrates in the southeast, covering southeastern Brazil, Uruguay, and northeastern Argentina. The primary trash fish species are Argentine anchovy along the eastern coast and Peruvian anchovy along the western coast. - Habitats and fishing grounds of Argentine anchovy in the southeast largely overlap with high EC areas. Published studies reported needle-shaped diatoms are the dominant diatom group here. - On the western coast, Peruvian anchovy is abundant but mainly processed into animal feed rather than consumed locally. Needle-shaped diatoms are not the dominant species in its habitats. ![[Argentine_anchovy.png]] _Fig. 4 Geographic distribution of habitats and fishing grounds for Argentine anchovy in South America, alongside dominant diatom species. Map adapted from: FAO, 2026. [https://www.fao.org/fishery/en/aqspecies/2916/en](https://www.fao.org/fishery/en/aqspecies/2916/en)_ --- ## Our ongoing work Our research focuses on exploring the potential association between consumption of trash fish, needle-shaped diatom silica frustules, and esophageal cancer epidemics. - We have completed sample collection and preliminary analysis of trash fish from multiple sites across China and Tanzania. Relevant findings are currently under submission for publication; a brief summary is available here: [DiatomNeedles_China_Tanzania_2026.pdf](https://www.dropbox.com/scl/fi/lep5c4ixjxsvecyondvrh/DiatomNeedles_China_Tanzania_2026.pdf?rlkey=3sduawx51p5pi0rivb2nev0e1&st=tb16t7m1&dl=0). - In May 2026, we collected a new batch of dried trash fish samples from local markets across East African countries (Tanzania, Kenya, Malawi, with high EC incidence) and West African countries (Cameroon, Ivory Coast, Nigeria, with relatively low EC incidence). - We will continue to collect representative and comparative trash fish samples from more high- and low-EC regions across Africa, East Asia, South Asia and South America. We welcome collaboration on sample collection and analysis. Please contact Mr. Wu Haisheng: [[email protected]](mailto:[email protected]) if you are interested in this project. ![[TrashFishCollection.png]] _Fig. 5 Global map of esophageal cancer incidence (Global Cancer Observatory, [https://gco.iarc.fr/en](https://gco.iarc.fr/en)) with marked trash fish sampling sites. Sampling coverage is expanding, and the map will be updated regularly._