Continuous Illumination at Increasing Light Intensities and the Effect on the Growth and Survival of Snubnose Pompano Trachinotus Blochii in the Early Stage

Abstract

The study investigated the influence of continuous illumination at increasing light intensities on feeding, growth, and survival of early-stage snubnose pompano larvae from 1 to 10-day post-hatching ( Fish larvae were exposed to 5 treatments with 3 replicates [T1 – natural indoor light; 12 hours light (hL): 12 hours dark (hD), T2 – 300-500 lux (lx), T3 – 300-1000 lx, T4 – lx, T5 – 300-3000 lx]. Newly hatched larvae were stocked at 15 ind. /L density and fed with enriched rotifers (Brachionus plicatilis; 50-250 µm) at 30 ind. /ml starting from 2 DPH. The number of rotifers in the digestive organ, feeding incidence, and total length of larvae were examined at 3-hour intervals from 0400 hour (H) to 2200H on 3 DPH, at 6-hour intervals from 4 to 5 DPH, and once on 8 DPH at 1000H. The fish final growth and survival were determined after the study. Results justified that snubnose pompano is a visual feeder and exhibits diel rhythm within 24 hours of light, while larvae at natural photoperiod usually undergo diurnal rhythms. However, changing light intensity conditions from low to high levels altered the feeding behavior of the fish larvae. Better and consistent feeding and survival of larvae were obtained at moderate continuous illumination at increasing light intensities (300-500 lx), but more remarkable fish growth can be obtained at higher light treatments (300-1000 lx, 300-2000 lx, 300-3000 lx). Adverse effects of higher light intensities on larvae survival were observed after 5 DPH.