Pyropia spp.

Pyropia or Porphyra spp. are commonly referred to as ‘nori’ and are most popular as thin sheets for sushi preparation.This group of species are red seaweeds that occur in the temperate zone. Pyropia spp. are comparably high value seaweeds, and farming and processing has a higher level of automation than other seaweed species. 

Common name: 
Laver, nori, gim

Scientific name: 
Several different species: Pyropia yezoensis,  P. seriata, P. dentata

Red seaweeds (Rhodophyta)

Pyropia spp. naturally occur in the intertidal zones, growing on the surface of rocks. For the entire life cycle, temperatures between 10 and 20°C are most suitable. Farming dates back to as early as the 1600s, yet industrial cultivation only began in the mid-1960s, when artificial seed production was established and synthetic nets developed soon after.


Pyropia in the form of the thin ‘nori sheets’ used for sushi rolls have become popular around the world in the past decades. In China, Korea and Japan the consumption of nori sheets has a much longer tradition and remains very popular today.

Beyond sushi, pyropia sheets are a popular snack available in all types of flavours. Toasted and seasoned they are used to roll any type of snack or rice for a quick bite. Furthermore cut up in smaller pieces, dry pyropia sheets are added to a wide variety of other snack foods, such as cookies.


Commercial Pyropia farming began in China in the 1960s. According to official data provided by the Chinese Fishery Statistical Yearbook, the production has steadily increased and in 2020 made up 222,000 tonnes dry weight, The FAO converts this into 2.2 million tonnes wet weight, using a conversion factor of 10 percent, however the wet-to-dry sheets ratio is in fact 5%.

Dry sheet output: 5.9 billion sheets were produced in 2021 according to official records.

Production outlook:  
Continuous growth seems unlikely, considering the existing high densities in most areas and the increasing governmental restrictions on expanding into new areas.

South Korea

Commercial farming since the 1960s. With the introduction of new species and expansion of culture grounds in the 1980s, the production grew significantly and has since reached an annual output of about 500,000 – 600,000 tonnes wet weight (Ministry of Oceans & Fisheries).

Today it is the most valuable farmed species within the Korean seaweed industry and the second most valuable marine product exported from Korea.

Dry sheet output: 1.57 million sheets in 2021

Production outlook:
Future growth of the current production is primarily constrained by limited space nearshore to expand the farms and shorter seasons due to climate change effects. Nevertheless the South Korean national breeding programme is dedicated to developing climate resistant and high quality cultivars that can sustain the strength of the industry.



Pyropia aquaculture production reached 480,000 tonnes wet weight in 1994 and has since gradually decreased, reaching about 250-300,000 tonnes wet weight in recent years. All Pyropia products are sold through the fishery cooperatives and the auction data provides the basis for the Consensus of Fisheries by the Ministry of Agriculture and Forestry of Japan.


Production outlook:
Future production in Japan is primarily constrained by the lack of labour, due to an ageing population and low level of automation in the Pyropia farming process.

The high-level supply chain overview for Pyropia

Input suppliers: farmers need equipment such as lines, ties, buoys and anchors, as well as seed material from dedicated hatcheries. Equipment is easily available through local shops, which provide all materials required to build the cultivation system.

Farmers: either companies or family farmers. Learn more about the farmers and the cultivation process in our farm insights chapter. In Japan and China, the primary processing is usually carried out by farmers or farming companies themselves with an automatic machine for dry nori sheet production.

Fisheries cooperatives: in South Korea all Pyropia farmers sell the freshly harvested seaweed straight from the harvesting vessel through the auctions that take place every morning during harvest season at the farmers’ cooperative port. In Japan, these sheets are sold through open tenders at the fishery cooperative’s auction and sent to department stores, restaurants and supermarkets.

Processors turn Pyropia into dry sheets, seasoned sheets or other types of snack products and sell packaged Pyropia products to wholesale markets and retail stores that sell them onwards to restaurants or directly to consumers for consumption at home.

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