Effect of ecofeed addition and inhibition of macroalge in mass seed production of asari clam Ruditapes philippinarum using sea water pond
2020
Kishioka, M. | Wanishi, A. | Murakami, D.
In order to improve the nutritional condition of asari clam, Ruditapes philippinarum in the culture pond (1.5 ha), utilization of ecofeed, produced from food residues discharged from food processing industry and out-of-date food from supermarkets and convenience stores, was examined in addition to fermented chicken feces. Total amounts of 34,800 kg and 31,800 kg of fermented chicken feces, 2,790 kg and 4,100 kg of ecofeed were spread over the pond in 2016 and 2017 respectively. There was no significant difference in growths of asari clam between 2015 and 2016, but degree of condition factor and population maturity rate were improved in 2017 compared with 2015. There were no significant changes in the contents of acid volatile sulfides (AVS), total nitrogen (TN), and total phosphorus (TP) in the bottom sediment during the period of the experiment. It was inferred that the accumulation of organic matters in the bottom sediment hardly progressed because ecofeed may be used directly or indirectly through wide variety of organisms in the pond. In previous studies, rapid increase of macroalgae such as genus Ulva and family Cladophoraceae often caused serious damage to asari clam by covering the bottom surface in the sea water pond. In order to solve this problem, the macro algae were killed by periodical dry-up around the shallow bottom of the pond and stirring the bottom using a trawling net.
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