Effects of age, size, and light intensity on spawning performance of pond-reared Penaeus merguiensis

The effects of prawn age, size, and light intensity on spawning performance of pond-reared Penaeus merguiensis were studied by inducing spawning of prawn broodstock by eyestalk ablation under two different light intensities (bright,1100 lx and dim, 2 lx) at three different known ages (7, 10, and 13 months old). For each age group (except the 13-month-old group), two distinguished size classes (large and small) were established to reveal the effect of prawn size. Results showed that light intensity did not affect spawning performance of prawns of different ages and sizes (P>0.05). In contrast, age had a significant effect on spawning performance of prawns (P<0.01). The overall spawning performance of the prawns increased from 7 to 10 months old and started to decline at 13 months old. Within the 7- and 10-month-old groups, larger prawns produced a superior overall spawning performance compared with smaller ones (P<0.01). Comparison across the size range of the experimental prawns showed that spawning performance improved with the increase of body size. However, the 13-month-old prawns, although having a similar size as large 10-month-old prawns, had an inferior spawning performance (P<0.01). Survival and growth of ablated prawns significantly decreased with the increase of prawn size and age (P<0.01). It is suggested that spawning performance of pond-reared P. merguiensis peaked between 10 and 12 months old, and broodstock should be bred during this period for hatchery production. (C) 2002 Elsevier Science B.V. All rights reserved.