水産養殖研究開発ジャーナル

概要

Effects of Natural Diet on Growth on White-Leg Shrimp Litopenaeus vannamei Under Experimental Mesocosms Emulating an Intensive Culture System

Bojórquez-Mascareño EI ,Soto-Jiménez MF *

A study of nitrogen (N) balance and stable isotopes was conducted to assess the impact of natural diet on white leg shrimp (Litopenaeus vannamei) under experimental mesocosms emulating an intensive culture system. We tested isonitrogenous diets by using commercial formulated feed (FF), natural food (NF) produced in the column water (FF+NF) and sediments (FF+NF+S) on earth ponds, and combinations 50:50 ratio based on N content. A followed study was conducted in three representative ponds at farm level. Specimens were tested for gain of weight, survival rate, specific growth rate (SGR) and parameters k and m and t50 in four trials, from post-larvae of twenty days (PL-20’s) to larger juveniles. Specimens raised on FF+NF+S and FF+NF treatments showed weight, SGR´s and survival significantly higher than shrimp raised on pure diets (FF and NF) and in ponds at the same time (p<0.05). Exceptions were observed for the larger shrimp (trial 4) with no significant differences. Feed conversion ratios (FCR) in organisms reared on combined diets were lower than FF diet. Based on isotope mixing model the relative contribution of the natural productivity varied among combined diets and trials. N contributions to growth of PL-20’s specimens were 18-74% for FF+NF and 25-62% for FF+NF+S treatments, decreasing with the shrimp size to <10% in largest juveniles. Comparable results were observed in ponds. Extrapolating our results to a farm level, farmers may be able to reduce FCRs and improve profitability by enhancing the natural productivity during the first weeks of an intensive shrimp farm culture. Stable isotopes of N were useful to assess changes in the isotopic signals of shrimp fed with different diets and thus, to determine the N source for shrimp growth.