高密度養殖蝦池間捕增產之研究

Abstract

在超高密度的池蝦養殖中，於中後期常因蝦池的現存量(Biomass)太高、蝦體的排泄、飼料的殘餌與腐敗導致水質劇變管理困難。其影響輕微者使蝦類生長緩慢、池蝦大小參差不齊、蝦病叢生、浪費飼料；而嚴重者甚至於發生部份池蝦死亡或全池死亡殆盡，功虧一簣，此種情形在多種病毒的爆發肆虐下尤為明顯。因此在本研究，引入現存量、生產載量的養蝦管理理論，並採行間捕的管理技術，以期能易化養蝦困境，增加池蝦產量，並提高經濟效益。 結果發現蝦池的水質環境與生產載量隨著養殖日期的增加，而有水質逐漸變差與蝦池最適生產載量的減少。其中特別是氨態氮的增加、溶氧量的降低與生長緩慢最為明顯。斑節蝦A池高密度養殖4個月的生長與間捕，使每公頃的產量達28公噸，池蝦大小為18-24公克。斑節蝦B池3個月的生長與間捕，使1公頃的產量達10公噸，池蝦大小為7-10公克。草蝦A池養殖由於水溫高，生長快速，二個月已長到50尾/斤(12公克) ，由於池釣蝦價太好，40尾/斤(15公克) 每公斤500元，故開始間捕出售15公克者，其總產量為每公頃7.13噸，由間捕的操作，每公頃增產1.65公噸，且體型亦大些、價格高些。 管理者除了增加換水量、多加水車使用量或施用藥劑或活菌酵素淨化水質外，間捕可維護蝦池的生產載量(carrying capacity)，減少養蝦風險，增加蝦池的生產量與經濟效益，水質亦較易維持與穩定，池蝦存活率提高。間捕後能使小個體的池蝦快速成長達上市規格。間捕雖會增加人工及網具支出，但相較之下仍值得，故間捕為目前最具效果的健康安全與提高產量的管理方式之ㄧ。

In shrimp ponds with highly intensive stocking density, at the middle and/or latter period, the high existing volume (biomass) of shrimp ponds, the excretion of shrimps, over-feeding and feed-corruption led to drastic changes in water quality. The slight effects are slow growing rate of shrimps, shrimp size differences, shrimp diseases and feed wasting. In some serious cases, the shrimps die partially or even completely. Therefore, in this study, the shrimp-farming management for existing capacity and high production, partial harvesting, were carried out in order to simplify the management of shrimp-farming, to increase production and to improve economic efficiency. The results showed that as the shrimp farming period passed by, the water quality and carrying capacity got worse gradually. In Kuruma shrimp (Penaeus japonicus) pond A, after four months the harvest per hectare increased to 28 tons, due to partial harvest, with the average body-size of 18-24 grams. Similarly in Kuruma shrimp pond B, the harvest per hectare was 10 tons, and the average body-size of shrimp was 7-10 grams after three months. Due to high temperature during the farming period, the growing rate of grass shrimp(P. monodon) pond A was very quickly, and after two months the total output was 7.13 tons per hectare. Because of the operation of partial harvesting, the output increased 1.65 tons per hectare, the shrimp body enlarged and the price increased. In addition to increase the water exchanging rate and application of biotics or water purification, the partial harvesting could maintain the production loading (carrying capacity), reduce farming risk, increase the output and benefits, simplify water quality management, increase the survival rate of shrimps and raise the growing rate of shrimps. Although the partial harvesting will increase the cost of farming, it is still worthy. Thus, the partial harvesting is one of the most effective management strategies increasing shrimp production.