of Porphyra yezoensis
As mentioned previously, the farming of nori occurs in two stages.
The first occurs indoors, from May to October, where the Conchocelis stage
is cultivated along with the production of conchospores. The second
stage occurs from October until May or April, where the framer focus
on the cultivation of the thallus in the field. The following will
provide a timeline sketch of how nori is farmed in China.
Cultivation of Conchocelis
Early and mid-May
- Carpospores are collected and seeded on mollusc shells (Meretrix
meretrix). The cultivation occurs in large elongated shallow
concrete tanks with 20-30 cm of seawater in depth. The seawater
has been subjected to sedimentation and the addition of nitrogenous
and phosphate nutrients. At this stage, the temperature is not
controlled and allowed to flunctuate with the air temperature.
However, optimal growth occurs between the temperatures of 20-25
- The carpospores develop to the Conchocelis phase, which
is responsible for creating conchospores. The conchospores will develop
into the thallus stage, which is then ready for harvesting.
Prof. Michael D. Guiry. Reuse of picture not permitted without prior
Mid-May to early June
Water temperature is raised to 22-23 degrees Celsius to encourage
vegetative growth of the Conchocelis phase.
Early July to late August
- The water temperature is raised again from 22-23 degrees Celsius
to 27-28 degrees in mid-August. After mid-August, the water temperature
is gradually decreased.
- In July, light intensity is reduced to encourage formation of conchosporangia,
which will eventually release conchospores.
Late August to late September
- Water temperature is dropped to 23 degrees during this period of
- Light intensity is held the same to encourage the formation of
the conchospores in conchosporangia.
- The light period is reduced to 8-10 hours by darkening the culture
Late September to mid-October
- Conchospores are present in late September.
- The mass discharge of conchospores occurs in early and mid-October.
- Once the conchospores are released, they are seeded on special
cultivation nets which are placed in the tanks.
- When 50,000 spores are being released a day, the light intensity
is increased slightly to encourage thallus germination.
- The water in the tanks are also agitated to move the spores and
to obtain an even distribution of conchospores on the cultivation
After the release of the conchospores, the cultivation processes
now focuses on the cultivation of the thallus of Porphyra. These processes
now occur outdoors, in the field, where the seaweed is now subject
to natural environment conditions.
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© 1999 Lisa Chen.
All rights reserved. Use for educational purposes permitted with acknowledgment