Effect of body weight on satiation time and predation rate in red swordtail, Xiphophorus helleri (Poeciliidae) fed on adult Artemia

Abstract

Satiation time and predation rate were studied in six different size groups (Group A : 0.016 g; B: 0 132 g; C: 0.309 g; D: 0.422 g; E: 1.057 g; F: 3.635 g) of the ornamental fish Xiphophorus helleri fed on adult Artemia under constant density. The satiation time increased with increase in size. A minimum of 17 minutes feeding duration was sufficient for the smallest size group tested and a maximum duration of 1 hour was required for the largest group (F size group). The maximum number and weight of prey organisms were consumed during the first 10 min of feeding and it gradually decreased in every successive 10 min in all weight classes of X helleri except the size group A. Animals consumed 78, 65, 64, 61 and 31% of total food during the first 10 min and it declined to 22, 30, 27, 17 and 30% during the second 10 min respectively in B, C, D, E and F size groups. However, the size group A predated 37% of prey during the first 10 min and it increased to 63% in second 10 min. The rate of predation was maximum (404 mg/g live fish) in the lowest size group tested (A) and minimum (49 mg/g live fish) in the largest size group (F). This high predation rate could have resulted in quick satiation in smaller size groups.