USO DE COPÉPODES NA ALIMENTAÇÃO DE LARVAS DE LINGUADO Paralichthys orbignyanus (Valenciennes, 1842)E OTIMIZAÇÃO DO CULTIVO DO COPÉPODE Acartia tonsa Dana, 1849.
The experimental rearing of the flounder Paralichthys orbignyanus has been carried out with relative success at the Estação Marinha de Aqüicultura - FURG, Rio Grande, RS, Brazil. Nevertheless, its large scale cultivation is still limited by frequent high mortality rates observed in larvicultures using rotifers and Artemia as live food. Recent studies have shown that copepods can be a good alternative as live food for fish larvae. However the existing copepod culture techniques need many improvements towards the development of reliable production systems. The objectives of this study were to evaluate the performance of P. orbignyanus larvae from the first feeding until the metamorphosis, under a diet composed by the copepod Acartia tonsa and also; to contribute for the improvement of copepods culture system by testing the influence of different diets and algal densities on the copepods egg production rates. P. orbignyanus larvae were reared in a 50 L tank during 22 days after hatching (dah) (S = 30, T = 22 °C). A. tonsa nauplii were offered through the 3° dah to the 19° dah, and after this period, copepodits and adults were included in the larval diet. Regarding the trial of the influence of different algal densities on the copepods egg production, the diatom Thalassiosira fluviatilis was offered at the following concentrations: 0, 5 000, 10 000, 20 000, 40 000 and 80 000 cels mL-1. To evaluate the influence of different diets on the egg production of A. tonsa, the microalgae Nannochloropsis occulata and Chaetoceros mulleri, and an inert diet were tested. The results showed that the flounder larvae were able to feed effectively on A. tonsa, completing the metamorphosis between the 19° and the 22° dah. The larval standard length (mm) in the 7° dah was 2.98 ± 0.20, 4.77 ± 0.24 in the 14° dah, and 4.90 ± 0.42 in the 22° dah. The density of the diatom T. fluviatilis had a high influence on A. tonsa egg production, reaching a maximum value at 80 000 cels mL-1 (~ 60 eggs female-1 24 h-1). Concerning the different diets tested, the copepods fed the artificial diet and N. occulata exhibited a very low egg production rate (~ 1 - 2 eggs female-1 24 h-1). On the other hand, the copepods fed on the diatom C. mulleri showed a relatively high egg production (22 eggs female-1 24 h-1); suggesting that this microalga represents a good choice for the cultivation of A. tonsa. Moreover, the size of this diatom (~ 7 ?m) allows its application on the feeding of both nauplii and adults, simplifying the copepods culture system.
Advisor:José Guilherme Bersano Filho; Andréa Santarosa Freire; Luís André Nassr de Sampaio; Erica Alves Gonzalez Vidal
School:Fundação Universidade Federal do Rio Grande
Source Type:Master's Thesis
Date of Publication:03/31/2006