High density effects on the growth, development and survival of Litoria aurea tadpoles

Abstract

Increased production of frogs is expected as markets increase and wild stocks dwindle. With conventional rearing techniques, high tadpole densities lower metamorphosis weight, and increase metamorphosis time (MT) and variation. These problems result from low water quality and competition for feed. In this study, tadpoles of Litoria aurea, a species with a similar ecology and physiology to commercial frog species, were reared at high to very-high densities (40, 80, 120, 160 and 330 l −1). Adequate dissolved oxygen was achieved with shallow water (1.2 cm), water was changed every 12 h, and the tadpoles feed to satiation. Individual weight and survival were calculated at 14-day intervals until first metamorphosis at 45 days. With increasing density, tadpole weight declined from 4.23±0.10 to 1.68±0.18 (g). Survival was greater than 85% for all densities except for 330 l −1 (64%). At metamorphosis, mean survival, metamorphosis time, and weight were calculated for densities of 40–180 l −1. The weight of juveniles (1.90–2.10 g) from the 40–80 l −1 densities compared favorably with that of wild juveniles (1.8 g). Metamorphosis time was 52–62 days, which compares favorably with the ≈100 days achieved by conventional techniques with commercial species at much lower densities (≈2 l −1). This study shows the use of high density rearing techniques with tadpoles; (1) produce consistently high quality metamorphs, (2) shorten rearing time and metamorphosis period, (3) potentially use water, feed and space more efficiently.