The mass cultivation of Ecklonia stolonifera Okamura was studied as a possible summer feed for the abalone industry in Korea for the period between August and November when Undaria and Laminaria are not available. Experiments were conducted to investigate the optimal conditions for artificial seed production and mass cultivation of this species. Seedlings of E. stolonifera were reared in an indoor tank for 60 days until they were around 500 μm in length. Following indoor tank culture, the seedlings were transferred in situ to a nursery culture area for 2 months, before begin transferred to the main grow-out area. The maximum growth and development of young thalli in nursery culture area occurred at 2 m depth, whilst maximum growth of thalli in the main culture area occured at 1.5 m depth. Production of E. stolonifera was between 3 and 9 kg wet wt. m −1 in the first year of culture after seeding and 12 to 13 kg wet wt. m −1 in the second year of culture, after management (depth control and fouling organism removal, etc.) of the holdfast. The relationship between optimal water depth for culture and underwater irradiance during the E. stolonifera cultivation was defined as: y =−0.331x+ 8.198 (r 2 =0.9903). The growth rates achieved in this trial indicate that E. stolonifera cultures could produce sufficient biomass to supply summer feed for the Korean abalone industry.
Sargassum fulvellum is a brown alga recently introduced to the seaweed cultivation industry in Korea. There is current interest in the commercial scale of aquaculture of this species. For the artificial seeding and cultivation of this alga, growth and maturation were investigated from September 2002 to August 2003. Indoor culture experiments for maturation induction were also conducted at temperatures of 5, 10, 15, 20 and 25 • C and irradiances of 20, 50, 80 and 100 μmol photons m −2 s −1 under 16:8 h (L:D) photoperiod. Within a given culture test range, higher temperature and irradiance levels favoured the maturation of receptacles in S. fulvellum. Using temperature and irradiance control for thalli, artificial seed production of this species could be done one month earlier than thalli matured in nature. Under natural condition, receptacle formation of the plants began in February, and the eggs were released from March to April. For mature thalli of 200 g wet wt., artificial seeding was complete enough for attachment on seed strings of 100 m. Mean production obtained from the artificial seeding technique in situ was 3.0 kg wet wt m −1 of culture rope during the cultivation period.
Codium fragile (Suringar) Hariot is an edible green alga farmed in Korea using seed stock produced from regeneration of isolated utricles and medullary filaments. Experiments were conducted to reveal the optimal conditions for nursery culture and out-growing of C. fragile. Sampling and measurement of underwater irradiance were carried out at farms cultivating C. fragile at Wando, on the southwestern coast of Korea, from October 2004 to August 2005. Growth of erect thalli and underwater irradiance were measured over a range of depths for three culture stages. During the nursery cultivation stage (Stage I), growth rate was greatest at 0.5 m depth (0.055±0.032 mm day −1 ), where the average midday irradiance over 60 days was 924± 32 μmol photons m −2 s −1 . During the pre-main cultivation stage (Stage II), the greatest growth rate occurred at a depth of 2 m (0.113±0.003 mm day −1 ) with an average irradiance of 248±116 μmol photons m −2 s −1 . For the main cultivation stage (Stage III) of the alga, thalli achieved the greatest increase in biomass at 1 m depth (7.2±1.0 kg fresh wt m −1 ). These results suggest that optimal growth at each cultivation stages of C. fragile could be controlled by depth of cultivation rope.
This study was aimed at determining the optimal depth and photon irradiance for growth of Sargassum fulvellum. Sampling and measurement of underwater irradiance were carried out at farms cultivating S. fulvellum at Wando, southwestern coast of Korea, from May 2004 to April 2005. Growth of thalli, underwater irradiance and photosynthetic quantum yield were measured over a range of depths for three culture stages. During their nursery cultivation stage (Stage I), length increase was greatest at 1.5 m depth (2.5±0.2 cm), where the average midday irradiance over 28 days was 488±58 μmol photons m −2 s −1 . During the pre-main cultivation stage (Stage II), the greatest length increase occurred at 1 m depth (10.9±0.1 cm) with an average irradiance of 845±169 μmol photons m −2 s −1 . For the main cultivation stage (Stage III) of the alga, thalli showed maximal length growth in March and early April at depths of 1-2 m and 3 m. These results suggest that growth at each cultivation stage of S. fulvellum could be controlled by depth of cultivation rope.
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