RESUMEN
The aim of this study is to characterize some population biology parameters of P. squamosissimus, A. altiparanae and S. maculatus, the dominant fish species of the Santa Bárbara River, a tributary of the Nova Avanhandava Reservoir, low Tietê River. Fish samplings were performed monthly between September/2002 and August/2003, using gill nets with different mesh sizes. Females of all species have larger standard lengths than males (Mann-Whitney, p
The aim of this study is to characterize some population biology parameters of P. squamosissimus, A. altiparanae and S. maculates, the dominant fish species of the Santa Bárbara river, a tributary of the Nova Avanhandava reservoir, low Tietê river. Fish samplings were performed monthly between September/2002 and August/2003, using gill nets with different mesh sizes. Females of all species have larger standard lengths than males (Mann-Whitney, p 0.0001), and are more frequent in superior size classes (Kolmogorov-Smirnov, p 0.0001). All populations presented isometric growth, but differences between males and females were observed. Only P. squamosissimus presented a gender ratio different from 1:1, with a higher proportion of males (1:2, 2, p 0.05). The onset of gonadal maturation occurs at 15 cm in P. squamosissimus, 9 cm in S. maculates and at 8.9 cm in A. altiparanae. In all species populations, the adults predominate over juveniles. The allometric condition factor (K) of P. squamosissimus and S. maculates presented higher values in the periods from March-May and June-August, and A. altiparanae in the period from March-May (Kruskal-Wallis, p 0.05). These results indicate that the populations successfully exploit the lentic environment, and present life cycle tactics adapted to their particular means of environment occupation.
RESUMEN
The effect of molasses addiction on carbon:nitrogen ratios (C:N) on the performance of Litopenaeus vannamei shrimp during the nursery phase cultured without water exchange was investigated. The C:N ratios were evaluated in 25:1 (25M) and 15:1 (15M) proportion and a control (0M), with no carbon source addition, in a randomized experimental design with four replicates. Post-larvae (PL) with initial weight of 2.5 ± 0.5 mg were stocked in 12 tanks (800 L net volume), at the density of 6.25 PL L-1 during 42 culture days. At the end of culture, the shrimps weights on 25M (532.0 mg) and 15M (540.0 mg) treatments were higher (p 0.05) than the 0M (428.6 mg) treatment. Shrimp survival was high in all treatments (77.9 to 90.0%), but without significant difference (p 0.05). Therefore, the 15 and 25:1 C:N ratios showed an increased growth performance of nursery phase L. vannamei post-larvae cultured without water exchange.
Investigou-se o efeito da adição do melaço nas relações carbono:nitrogênio (C:N) sobre o desempenho zootécnico do camarão Litopenaeus vannamei, na fase berçário, quando cultivado sem renovação de água. As relações do C:N foram avaliadas nas proporções de 25:1 (25M), 15:1 (15M) e o controle (0M), sem aplicação de carbono, em delineamento experimental inteiramente casualizado, com quatro repetições. Pós-larvas (PL) com peso inicial de 2,5 ± 0,5 mg, foram estocadas em 12 tanques (800 L volume útil), em densidades de 6,25 PL L-1, durante 42 dias de cultivo. Ao final do cultivo, os pesos finais dos camarões dos tratamentos 25M (532,0 mg) e 15M (540,0 mg) foram superiores (p 0,05) aos do tratamento 0M (428,6 mg). A sobrevivência dos camarões foi satisfatória em todos os tratamentos (77,9 a 90,0%), mas não houve diferença significativa (p 0,05) entre os mesmos. Desta forma, conclui-se que as relações C:N de 15 e 25:1 são mais eficientes ao propiciarem melhor desempenho no crescimento das pós-larvas de L. vannamei cultivadas na fase berçário sem renovação de água