Efeito do fotoperíodo na sobrevivência e crescimento de larvas e juvenis do linguado Paralichthys orbignyanus.
The objective of this study was to evaluate the effects of photoperiod on the rearing of larvae and juvenile flounder Paralichthys orbignyanus. Three experiments were done (EXP1, EXP2, and EXP3), the first two studied the larval stage and the last the juvenile stage. In a preliminary evaluation (EXP1) three photoperiods were tested: 0, 12, and 24 hours of light (hL) with two replica each, it lasted for five days. EXP2 evaluated two photoperiods: 18 and 24 hL with three repetitions each, it lasted for 30 days. In EXP3 four photoperiods were tested: 0, 12, 18, and 24 hL with four repetitions each, it lasted for 35 days. In EXP1 and EXP2 larvae were reared in cylindrical tanks with flat bottom. Water volume was 10L, stocking density was 50 larvae/L, rotifers and artemia were offered as live prey in a green water system, 50% of the water was exchanged daily. In EXP3 juveniles were reared in cylindrical tanks with flat bottom filled with 50L of water, in a flow-through system with capacity to exchange 200% of the water daily. Metanauplii of artemia were offered as live food. Survival and growth were proportional to the photoperiod in EXP1, no survivors were observed five days after hatching in the dark (0 hL), and 1.6 and 4.5% survived in 18 and 24 hL respectively. Notochord length was equal to 3.44±0.4 and 3.75±0.3mm for 18 and 24 hL respectively. Survival in EXP2 was also proportional to the photoperiod, 4 and 13% respectively for 18 and 24 hL. Growth was higher in 24 hL during the larval stage, but as the flounder metamorphosed, those individuals reared in 18 hL achieved a better growth rate. Final length was equal to 12.7±1.9 and 11.6±1.4mm respectively for 18 and 24 hL respectively. In EXP3, survival was equal to 38±14, 69±11, 69±6, and 81±9% respectively for 0, 12, 18, and 24 hL. Final weight was equal to 21.8±4.5, 114.0±3.7, 132.7±3.8, and 105±3.5mg respectively for 0, 12, 18, and 24 hL. The results obtained in this study suggest that larval flounder should be reared with constant illumination until 15-20 days after hatching, but older larvae and juvenile will have a better performance with 18hL.
Advisor:João Carlos Brahm Cousin; Luís André Nassr de Sampaio; Vinicius Ronzani Cerqueira
School:Fundação Universidade Federal do Rio Grande
Source Type:Master's Thesis
Date of Publication:06/28/2004