PROBLEM TO BE SOLVED: To provide a raising agent that effectively supplies, even in a culture fishery where water flows, much-needed nutritional components to cultured laver which is frequently discolored due to lack of nutritional components in seawater, so that sound growth is secured to prevent the discoloring.SOLUTION: A sustained-release raising agent composition for laver culture has nutritional components dispersed and held in a biodegradable sustained-release base such as polyvinyl alcohol, the nutritional components containing desired kinds of principle elements indispensable for the growth of laver and trace elements indispensable for the synthesis of pigments of laver. Even when administered in seawater where water flows, the nutritional components elute gradually in a short time without being dissolved, diffused or flowing out, and necessary amounts of nutritional components can be continuously supplied to cultured laver in a fishery over a desired period of time.【課題】海水中の栄養成分の不足欠乏から色落ちを頻発している養殖海苔に対して、不足欠乏している栄養成分を水流のある養殖漁場でも有効に供給し良好な生育を確保して色落ちを防止する育成剤の提供。【解決手段】海苔の生育に欠かせない主要元素や海苔の色素合成に欠かせない微量元素の所望種類を含む栄養成分をポリビニルアルコールなど生分解性のある徐放性基剤の中に分散保持させた海苔養殖用徐放性育成剤組成物であって、水流のある海水中に投与した場合にも栄養成分が短時間で溶解・拡散・流失せずに徐々に溶出し、漁場の養殖海苔に対して栄養成分の必要量を所望時間に亘って継続して供給することができる。【選択図】なし
