61 Some aspects of nursery rearing of the Asian seabass (Lates calcarifer, Bloch) in indoor cement tanks K. K. PHILIPOSE, S. R. KRUPESHA SHARMA, N. SADHU, N. G. VAIDYA AND G. SYDA RAO* Karwar Research Centre of Central Marine Fisheries Research Institute, Karwar - 581 301, Karnataka, India *Central Marine Fisheries Research Institute, Kochi - 682 018, Kerala, India e-mail: kkphilipose@gmail.com ABSTRACT Asian seabass (Lates calcarifer) is a highly valued food fish of great culture potential. Nursery rearing of Asian seabass in indoor cement tanks was undertaken. Fish were fed on artificial diets at 4% body weight and four times feeding per day with periodical size grading. Mean weight and length at the end of the 45 days experimental period was 8.55 g and 91.03 mm, respectively. While survival rate was 100%, FCR and PER at the end of the 45 days experimental period was 1.15 and 1.07%, respectively. The results of various growth parameters studied showed that the values obtained were in conformity with earlier reports on nursery rearing of Asian seabass under varied rearing systems and growth conditions. Keywords: Asian seabass, Lates calcarifer, Nursery rearing Introduction Asian seabass Lates calcarifer, also known as barramundi, is a catadramous species widely distributed in the Indo-West Pacific region from the Persian Gulf, throughout south-east Asian countries to Australia. Seabass has been cultivated in brackish as well as freshwater ponds and marine cages in many south-east Asian countries (Cheong, 1989). Asian seabass is an ideal aquaculture candidate species due to its high demand and rapid growth, and has been cultured successfully in Australia since 1980s (Partridge, 2008). Though cage culture technology for seabass has been established, grow-out techniques in ponds are still at infancy. Asian seabass is a potential candidate species in India for rearing in closed recirculating systems as well as in floating cages because of its fast growth rate, ability to adapt to varying environmental conditions and its demand in domestic as well as export markets. While many published reports are available on nursery rearing of L. calcarifer, reports on work done in India are scarce. The present study was conducted on growth performance and survival of seabass during nursery rearing in cement tanks, fed on artificial diets. Materials and methods L. calcarifer fingerlings Ten thousand hatchery produced fingerlings of L. calcarifer were brought from Rajiv Gandhi Centre for Indian J. Fish., 57(4) : 61-64, 2010 Aquaculture, Sirkazhi, Tamil Nadu. The fingerlings (weight: 2.01 ± 0.53 g; total length: 55.58 ± 4.64 mm) were packed in aerated polythene bags (50/bag) containing 5l of seawater (salinity 28 ‰; pH: 7.8:, temperature: 28 O C) and transported to the nursery rearing tanks at Kumta, Karnataka by road. The transportation time was 19 h. Rearing system Immediately on arrival, the fishes were given a freshwater dip and placed in four cement tanks each of size 10’ X 6’ X 5’ containing 7000 l of seawater (2500 fingerlings/ tank) with continuous aeration. The juveniles were reared in nursery rearing tanks upto 45 days before they were shifted to open sea cages for further experiments. Feeding regime From second day onwards, the fish were fed commercial fish feed with a pellet size of 0.5 mm diameter at 4% of the body weight, four times a day (6.00 am, 12.00 pm, 6.00 pm and 12.00 am) for the first 15 days. Then the pellet size was increased to 1 mm for next 15 days while the feeding rate and frequency remained unchanged. For the remaining 15 days, the fishes were fed with a pellet size of 2 mm. Proximate analysis of the feed was done in the beginning of the experiment (AOAC, 1975). Eighty per cent of the water was replaced 5 min after feeding with 20 min flow -through thereafter. It was confirmed that the feed was consumed immediately after feeding with no visible feed pellets settled at the bottom.