Croatian Journal of Fisheries (Mar 2012)
REARING CARP LARVAE (Cyprinus carpio) IN CLOSED RECIRCULATORY SYSTEM (RAS)
Abstract
Postembryonic rearing of carp larvae in closed recirculatory system was conducted in 2009 at the fish farm Ribnjak LLC, Donji Miholjac, Croatia. The research was conducted in two test groups (A and B with three iterations in each) with a control group (C). Test group A (3 tanks x 250 l) consisted of 150 000 larvae (density of 200 larvae•l-1), test group B (3 tanks x 500 l) consisted of 600 000 larvae (density of 400 larvae•l-1), and the control group (C) was a mud fish pond T-6 which was stocked by 800 000 larvae•ha-1 under standard production conditions. In this research, basic physical and chemical water parameters were controlled (temperature, oxygen, pH, total ammonia and nitrites). Initial measuring of carp larvae total length (TL) was conducted prior to their placement into tanks (N=120). On the fourth, sixth, eighth and tenth day of research 20 larvae (N=140) were taken out of every tank as well as out of control group and measured. Feeding with live feed began on the third day after hatching (larval TL 6.00±0.36 mm). Ten minutes after feeding live feed to larvae for the first time, 20 larvae (N=120) were taken out of every tank and a high portion of larvae that accepted live feed (89.17±3.76%) was determined by a magnifying glass. Feeding artificial feed began on the seventh day after the hatching. After ten minutes, a high portion of larvae who accepted artificial feed (96.67±2.58%) was determined. Since the end of the research, the determined length increment (ITL) per day was 0.41±0.04 mm, a very high survival rate was established (group A: 96%, group B: 93%). Feeding frequency was four times a day in five-hour intervals (at 06:00, 11:00,16:00 and 21:00 hours). The research was terminated after ten feeding days due to deteriorating condition of zoohygienic filter. The total of 3807 g of live feed and 1080 g of artificial feed was used.
