Feeding protocol with live feed and inert diet to determine the ideal age/size for weaning mullet Mugil liza (Valenciennes, 1836).

The Lebranche mullet Mugil liza is a marine fish of great importance for artisanal and industrial fishing, as well as aquaculture. The use of live feeds during the larviculture phase of marine fish is a significant component of production costs. The present study evaluated the effects of the feeding transition on different larval stages of M. liza, from the combined supply of live feed (Brachionus rotundiformis + Artemia franciscana) and live + inert feed (Artemia franciscana + inert diet) until the weaning phase to only the inert diet. A total of 3240 M. liza larvae (weight 0.0133 ± 0.0062 g and length 0.793 ± 0.160 cm) were distributed among the 12 experimental units (n = 270), resulting in four groups with three replicates each. Treatment groups consisted of feed transition with A. franciscana (enriched metanauplii) to commercial inert feed starting weaning at four different larval ages: 28, 31, 34, and 37 days post hatching. Zootechnical performance indexes and intestinal histomorphometry were evaluated. Mortality, condition factor, and length variation coefficient did not show significant differences between treatments. Final weight, final length, weight gain, and length gain were significantly greater in larvae that started weaning at 31, 34, and 37 days post hatching. Weight coefficient of variation was significantly higher in larvae that started weaning at 28 days (67.51 ± 11.70) compared to 37 days (34.40 ± 7.30). In intestinal histology, villi height (180.3 ± 4.4) was significantly higher in larvae that started weaning at 37 days post hatching. Considering the evidence found in the present study, it is recommended to start weaning M. liza on the 31st day post-hatching, using a 2-day co-feeding protocol (31st and 32nd days). From the 33rd day after hatching, M. liza larvae can receive only commercial feed.

Amyloodiniosis in farmed Sardinella brasiliensis (Steindachner, 1879): Case report of successful therapeutic control with copper sulfate.

Brazilian sardine is emerging as a promising species in Aquaculture. This study describes for the first time a case of parasitic infestation by Amyloodinium in Brazilian sardines Sardinella brasiliensis obtained from natural spawning in captivity. The sardines kept in nurseries were naturally parasitized by the amylodiniosis causative agente the dynoflagellate A. ocellatum with high mortalities above 50%. Fish presented clinical signs characteristic of amyloodiniosis which included easily perceived behavioral changes such as loss of appetite, scraping of the body against objects, walls and bottom, nursery pipes, agglomerations near the aerators and water inlets, presented with accelerated opercular beating and erratic swimming. For therapeutic treatment copper sulfate was used for 10 days. At the end of the treatment period the fish had no clinical signs or presence of the parasite on the body surface, indicating that the application of copper sulfate in concentration of 0.2 mg L-1 of Cu+ was effective to control this parasite, apparently without causing damage to Brazilian sardine.

17α-Methyltestosterone implants accelerate spermatogenesis in common snook, Centropomus undecimalis, during first sexual maturation.

The common snook, Centropomus undecimalis, is an emerging species for intensive fish culture, however, some reproductive aspects of this species, especially the development of the testes and the action of androgen hormones on spermatogenesis have not been studied. The objective of this study was to evaluate the effects of 17α-methyltestosterone (MT) on spermatogenesis and steroidogenesis during the first sexual maturation of the common snook. The fish, which were reproduced in captivity, had a body weight of 305.80 ± 35.60 g and a total length of 34,11 ± 1,08 cm. We used ethylene-vinyl-acetate (EVAc) implants with four concentrations of the hormone MT: T1 (0.3 mg/kg); T2 (3.0 mg/kg); T3 (15.0 mg/kg) and T4 (30.0 mg/kg), and a control group that did not receive the hormone. The gonads increased (P < 0.05) in relation to the concentrations of MT. Histological analysis revealed a progression of spermatogenesis in the MT treatments, especially in T3 and T4. Sperm release was attained in some fish treated with MT. However, there was a partial suppression of the levels of testosterone (T) and 11-ketotestosterone (11-KT) in plasma in the MT treatments, indicating a negative feedback on steroidogenesis. However, this suppression of T and 11-KT in plasma did not prevent an increase in the gonadosomatic index and the progression of gametogenesis. There was also an increase of estradiol (E2) in plasma in the treatments with the highest MT concentrations. The results suggest that the application of EVAc implants with MT at concentrations of 15 and 30 mg/kg stimulates the development and growth of the testes and accelerates spermatogenesis.

Ontogeny of the digestive tract of Centropomus parallelus larvae.

Development of the digestive tract and accessory glands of larvae of the fat snook Centropomus parallelus was examined under light microscopy, from hatching to 60 day post-hatching (dph). At hatching, the digestive tract is straight and composed by a cubic cell layer. The exogenous feeding starts at 3 dph, concomitantly with the mouth opening and subdivision of the rudimentary stomach and esophagus. At 4 dph, the intestine has three sectins, and vacuoles are observed in the posterior section, indicating the beginning of protein digestion and absorption. The pharyngeal teeth appear at 9 dph, and goblet cells appear at 13 dph in the esophagus. Gastric glands appear at 30 dph, marking the beginning of weaning. The disappearance of supranuclear vacuoles in the posterior intestine occurs at 35 dph, suggesting efficiency of extracellular digestion. This study shows that C. parallelus larvae is able to start weaning 15 days earlier than reported in earlier studies, increasing the success of larviculture.

Cultivation of juvenile fat snook (Centropomus parallelus Poey, 1860) fed probiotic in laboratory conditions

The objective of this study was to investigate the growth of juvenile fat snook (Centropomus parallelus) in laboratory conditions when fed a diet supplemented with the probiotic Lactobacillus plantarum. Changes in the intestinal flora, haematological parameters and growth performance were assessed using 180 fishes (54.2 ± 13.4 g each). The fishes were subjected to two treatments divided into six cages: 1) feed supplemented with probiotic, and 2) feed without probiotic (control). The temperature, dissolved oxygen and salinity were maintained at 25 ± 1 ° C, 4.0 mg.L-1 and 33 ‰, respectively. After 10 weeks of culture, the fishes fed probiotic had reduced viable culturable heterotrophic bacteria and Vibrio spp. and increased lactic acid bacteria in the intestinal tract, as well as a higher number of thrombocytes, leukocytes and lymphocytes in the blood. No significant difference was observed in the growth, survival or body composition, but the hepatosomatic index was significantly higher in the fishes fed with probiotic and control.

Egg Development of Paralichthys orbignyanus (Valenciennes, 1839)

Através do cultivo de ovos do linguado Paralichthys orbignyanus, obtidos de reprodução induzida em laboratório, foram descritos pela primeira vez seus estádios de desenvolvimento. O ovo era livre e flutuante, caracteristicamente pelágico. Além disso, tinha formato esférico, córion liso, espaço perivitelino estreito, vitelo homogêneo, e uma única gota de óleo. Seu diâmetro médio era de 0,792 mais ou menos 0,008 mm e o da gota de óleo de 0,114 mais ou menos 0,003 mm. Cerca de 1 h após a fecundação observou-se o blastodisco e em seguida a segmentação celular. A blástula iniciou após cerca de 5 h e a gástrula após 9 h. Com aproximadamente 20 h observou-se o fechamento do blastóporo. A nêurula ou embrião na fase inicial ocorreu após 24 h. Com cerca de 40 h havia batimentos cardíacos e movimentação da cauda do embrião. A eclosão ocorreu num período de 40 a 50 h após a fecundação, em temperaturas de 18 a 20 ºC. A larva tinha um comprimento total médio de 2,04 mais ou menos 0,024 mm, o saco vitelino bastante volumoso, a gota de óleo em sua porção posterior e pigmentação reduzida e esparsa. Estes resultados foram muito similares aos observados anteriormente em outras espécies congêneres.

Validation of an ovarian biopsy method for monitoring oocyte development in the fat snook, Centropomus parallelus Poey, 1860 in captivity

A validação de um método de biópsia ovariana para determinação in vivo da maturação ovocitária em Centropomus parallelus foi descrita. Os diâmetros de ovócitos, obtidos de amostras intra-ovarianas sifonadas por cânula, foram analisados a fresco e preservados com formalina (1%) em solução de NaCl (0,7%). Ovócitos em diferentes estádios de maturação estavam presentes ao longo dos ovários, até o estádio de vitelogênese completa, apresentando uma distribuição de freqüência de diâmetros unimodal. O diâmetro médio dos ovócitos não diferiu significativamente entre as quatro regiões dos ovários (P > 0,05). Amostras obtidas com a cânula são representativas da porção central do ovário, uma vez que as amostras in vivo e in vitro das sete fêmeas examinadas não foram significativamente diferentes (P > 0,05). Uma estimativa do coeficiente de variação corrigido para "bias" (P < 0,05) para oito amostras repetidas in vivo foi de 1,9 ± 0,6. Os resultados demonstraram que para esta espécie, este método de biópsia é satisfatório, provendo amostras representativas dos ovários.