Effects Of Meal Frequency On Growth And Reproduction In The Ornamental Red Swordtail, Xiphophorus Helleri

Abstract

Experiments were performed to investigate the influence of meal frequency on growth, gonad weight and fertility in an ornamental fish, the red swordtail Xiphophorus helleri. Five groups of uniform-sized 30-day juveniles (0.04±0.01 g, 13.10±0.61 mm) were fed either one meal in 3 days (1/3), one meal in 2 days (1/2), one meal a day (1/1), two meals a day (2/1) or three meals a day (3/1) for 210 days. Group 3/1 had the highest mean body weight throughout the experiment, fol- lowed successively by groups 2/1, 1/1, 1/2 and 1/3. The growth rate was higher in all groups before breeding began and drastically declined afterwards; the significant reduction might have been due to the diversion of assimilated food energy to fry production. The gonad weight and gonadosomatic index (GSI) increased with the increase in meal frequency and as the rearing period progressed. Fish in groups 1/1, 2/1 and 3/1 began to develop gonads on day 42 and reached the breeding stage on day 70; fish in 1/2 and 1/3 began to develop gonads on days 70 and 98 and reached the breeding stage on days 98 and 112, respectively. The increase in meal frequency significantly reduced the interbrood interval and fertility. Fish in group 3/1 produced the highest number of fry (704). Those in groups 2/1, 1/1, 1/2 and 1/3 released 450, 372, 70 and 8 fry, respectively. Groups 3/1, 2/1, 1/1, 1/2 and 1/3 bred four, three, three, two and one times, respectively. Based on the present study, three meals a day is optimum for X. helleri growth and reproduction in a culture system.