RESUMO
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.
RESUMO
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.
Assuntos
Antiprotozoários/uso terapêutico , Sulfato de Cobre/uso terapêutico , Dinoflagellida/efeitos dos fármacos , Doenças dos Peixes/prevenção & controle , Peixes , Infecções Protozoárias em Animais/prevenção & controle , Animais , Aquicultura , Brasil , Doenças dos Peixes/parasitologia , Infecções Protozoárias em Animais/parasitologiaRESUMO
ABSTRACT The present study aimed to evaluate nitrate acute toxicity in cultured common snook Centropomus undecimalis juveniles. Fish (20.35±6.10 g and 13.90±1.75 cm) were submitted to a control treatment (without nitrate addition) plus 20 increasing concentrations of nitrate up to 2735 mg L-1 obtained by sodium nitrate. System was semi-static, with 100 % daily water renewed and sodium nitrate addition to maintain the respective concentrations. Water temperature was 20.99±0.55 °C, dissolved oxygen 6.79±0.21 mg L-1, pH 8.23±0.10, alkalinity 141.80±7.68 mg L-1 CaCO3, salinity 33.47±3.75 g L-1, total ammonia and nitrite less than 1 mg L-1. During experimental period (96 h), no mortalities were observed in fish with or without nitrate addition. Compared to other species, the common snook presents higher tolerance to nitrate exposition. Based on the present findings, the acute nitrate exposure up to 2735 mg L-1 does not present lethal risk for common snook juveniles.
RESUMEN El presente estudio tuvo como objetivo evaluar la toxicidad aguda de nitrato en juveniles cultivados del róbalo común Centropomus undecimalis. Los peces (20,35±6,10 g y 13,90±1,75 cm) se sometieron a un tratamiento control (sin adición de nitrato) además de más de 20 concentraciones crecientes de nitrato hasta 2735 mg L-1 obtenidas con nitrato de sodio. El sistema era semiestático, con 100 % de renovación diaria de agua y adición de nitrato de sodio para mantener las respectivas concentraciones. La temperatura del agua fue 20,99±0,55 °C, oxígeno disuelto 6,79±0,21 mg L-1, pH 8,23±0,10, alcalinidad 141,80±7,68 mg L-1 CaCO3, salinidad 33,47±3,75 g L-1, amoníaco total y nitrito menor que 1 mg L-1. Durante el período experimental, no se observaron mortalidades en peces con o sin adición de nitrato. Comparado con otras especies, el róbalo común es más resistente a exposición de nitrato. Con base en los hallazgos actuales, la exposición aguda a nitrato hasta 2735 mg L-1 no presenta un riesgo letal para los juveniles de róbalo.
