Growth of the Pacific white shrimp, Litopenaeus vannamei, under an intensive farming system

Abstract

This research work aimed at evaluating the influence of the onset of cultivation, geographical position and stock density on the growth rate of the Pacific white shrimp, Litopenaeus vannamei, reared from postlarva through to its commercial size. The databank refers to 136 production cycles carried out in 13 ponds of a commercial shrimp farm from October, 2001 to July, 2007. The intensive rearing system was adopted with a mean farming period of 23.19 ± 1.07 weeks leading to a mean final weight of 14.09 ± 9.64 g. For the purposes of statistical analysis of the growth rate the data were grouped according to the following treatments: onset of cultivation, on the first and second semesters of the year; stock density, as ≤ 60 shrimps.m-2 and > 60 shrimps.m- 2; farming site, considering areas to the north and south of the supply channel. Individual mean weight (g) per week was the analyzed variable, fitted to regression equations for the comparison of growth rates through the regression slope submitted to the F-test and Student’s t test. The results are as follows: (1) there is a statistical difference in growth between the semesters (t = - 8.480; P < 0.01; F = 63.78; P < 0.01), the higher rate having been found to occur during the second semester (b = 0.996), probably on account of the water salinity’s stabilization; (2) the growth rate was quicker for a stock density of ≤ 60 shrimps.m-2 (b = 0.995), after the tests results, namely t = 9.405 (P < 0.01) and F = 44.52 (P < 0.01); (3) the growth rate was higher in the area to the north of the supply channel, with a statistical significance borne out by the values of t = 4.209 (P < 0.01) and F = 25.57 (P < 0.01).