Density optimization of pearlspot, Etroplus suratensis (Bloch, 1790), fry and fingerlings for live transportation

Aim: The study aimed to identifying optimal stocking densities and transport durations of Pearlspot (Etroplus suratensis) of varying sizes (1–3 inches) in closed, oxygenated systems. Methodology: Pearlspot fry and fingerlings were transported for 6, 12, 18, and 24 hr in 30 l polythene bags containing 5 l of oxygenated 15 ppt brackishwater. In Trial one, 1-inch fry (2.5-2.7 cm) were packed at stocking densities of 20, 40, 60, 80 and 100 fish l-1. In Trial two, 2-inch fry (5.0-5.5 cm) were packed at 20, 40 and 60 fish l-1, while in Trial three, 3 inch-fingerlings (7.3-7.9 cm) were packed at 10, 20 and 30 fish l-1. An oxygenated-water-only treatment was maintained as the control in all trials. Bags held in thermocol boxes, and survival and water quality (temperature, salinity, pH, dissolved oxygen, ammonia) were assessed pre-packing and post-transport. Results: A 1-inch fry, survived above 99% up to 18 hr at of 20–60 Nos. l-1, with the 20 Nos. l-1 supporting 99.0% survival at 24 hr. A 2-inch fry, survived 97% up to 12 hr at 20 and 40 Nos. l-1 but dropped sharply at higher densities. A 3-inch fingerlings were most sensitive, tolerating only 10 nos. l-1 for 6 hr before survival declined to 0% by 24 hr. Interpretation: Optimal stocking densities for transporting fry and fingerlings over short and long distances, benefit seed producers and farmers. Key words: Etroplus suratensis, Live transport, Pearlspot fry, Transit time, Water quality