Rodrigo Takata

Effect of water temperature and prey concentrations on initial development of Lophiosilurus alexandri Steindachner, 1876 (Siluriformes: Pseudopimelodidae), a freshwater fish

The aim of this study was to investigate the effects of water temperature and prey concentrations (Artemia nauplii) on the initial development of Lophiosilurus alexandri larvae. The experiment was conducted using a 4 x 2 factorial design, with four water temperatures (23, 26, 29 and 32 °C), two different initial prey concentrations (P700 and P1,300) and three replicates. Feeding was increased during the fifteen-day experiment. At the end of the experiment, the survival and condition factor were affected only by prey concentrations, with elevated numbers of Artemia nauplii leading to higher averages of these variables. The total length (TL) and specific growth rate were separately influenced by temperature and prey concentration, without interaction between them, and weight showed an interaction with these factors. In general, an increase of temperature (23 to 32 °C) improved the growth and nitrogen gain in L alexandri larvae. For TL, the optimal temperatures estimated were 31.4 and 31.0 °C for P700 and P1,300, respectively. Similar mean body weight larvae and nitrogen gain were observed at 23 °C for both levels of prey concentrations. For other temperatures, the P1,300 level provided greater weight gain for L. alexandri. Therefore, it is suggested that temperatures between 29-32 °C combined with a higher level of prey concentration maximise the development and nitrogen gain in L. alexandri larvae. Moreover, this is the first result about nitrogen incorporation in neotropical fish larvae.

Água levemente salinizada aumenta a eficiência da larvicultura de peixes neotropicais

The objective of this work was to evaluate the effect of slightly saline water in an intensive larviculture of tambaqui, matrinxa, apaiari, and piau, during the initial days of active feeding. Larvae were reared in artificial saline water, at concentrations from 0 (freshwater) to 14 g L ‑1 NaCl (at a 2.0 g L ‑1 ), and fed with two portions of Artemia nauplii, following a specific protocol for each species, in a completely randomized design, with 3 replicates. Tambaqui, matrinxa and apaiari larvae can be reared at saline concentrations till 2 g L ‑1 without impairing growth and survival. Piau larvae were more tolerant and endured saline water until 4 g L ‑1 . At saline concentrations above that, fish mortality increased and reached 100% at 6 g L ‑1 , for matrinxa and apaiari, and at 10 g L ‑1 , for tambaqui. Saline water at 2 g L ‑1 provided a higher survival for matrinxa, and higher growth for tambaqui, apaiari and piau. These last two species showed a better growth performance with the highest quantity of nauplii. Slightly saline water at 2 g L ‑1 is beneficial to these studied species, as it optimizes larval

Stocking density in the larviculture of Nile tilapia in saline water

The objective of this study was to assess the possibility of increasing the stocking density in the larviculture of Nile tilapia, Oreochromis niloticus, in saline water. Six-day post-hatched larvae (average weight of 0.09±0.002 g), at the start of the exogenous feeding, were stocked in twelve 8 L tanks at densities of 1, 10, 20 and 30 larvae/L. The larvae were fed a diet consisting of 40% crude protein five times per day. During larviculture, water was kept at a salinity of 2 g of common salt/L. At the end of the 28-day experiment, the survival rate, length, weight, temperature, water salinity and conductivity were not affected by the different treatments. The dissolved oxygen and pH, however, decreased as density increased, whereas total ammonia concentration, turbidity and biomass showed a direct relationship with the increase of stocking density. Consequently, the present study shows for the first time that the larviculture of Nile tilapia is possible with up to 30 larvae/L in water with 2 g of salt/L.

Frequência alimentar e taxa de arraçoamento durante o condicionamento alimentar de juvenis de pacamã

The objective of this work was to evaluate feeding frequency and rate during feed training of pacama juveniles. Feeding for three or four times a day and the feeding rates at 50, 75 and 100% of biomass were tested. Feeding management did not affect fish growth, survival, mortality, and cannibalism. Lack of management effect was kept when animals were fed extruded feed threefold a day, during 30 days. Feeding rate at 50% of biomass and threefold-a-day feeding can be used for the feed training of pacama juveniles.

Biological responses of Neotropical freshwater fish Lophiosilurus alexandri exposed to ammonia and nitrite

This study aimed to elucidate the responses of the Neotropical fish Lophiosilurus alexandri exposed to ammonia and nitrite, following a period of recovering. Acute toxicity tests lasted 96h, subchronic toxicity tests lasted eight days and the detoxification trial lasted four days. Groups of 12 juveniles were maintained in 90-L tanks and treated with increasing concentrations of ammonia and nitrite, except during the recovery test. All treatments were performed with two replicates. The median lethal concentrations (LC50) of 24, 48, 72 and 96h were estimated at 30.12; 24.35; 19.24 and 18.68mg·L-1 TA-N; 5.37; 4.57; 3.75 and 3.66mg·L-1 NH3-N and 20.37; 7.78; 7.09 and 5.86mg·L-1 NO2--N, respectively. The NO2- caused significant decrease in hematocrit and increase in the urea levels during short-term exposure, with recovery of homeostasis after the subchronic and detox period. Acute exposure to ammonia increased the enzyme profile of transaminases, glucose and urea. Urea concentration remained high in the subchronic and detox tests. Histopathologies were observed in animals exposed to ammonia in both toxicity tests. It was highlighted detachment of epithelium, hyperemia and necrosis in the gills. Exposure to NO2- caused epithelium detachment and aneurysm. Vacuolization and swelling of hepatocytes were the most common injury for both nitrogenous compounds. We concluded that the L. alexandri has moderate tolerance to ammonia and nitrite. The recovery period revealed remedial response to ammonia and nitrite exposure.

Description of amino acid and fatty acid content during initial development of Lophiosilurus alexandri (Siluriformes: Pseudopimelodidae), a carnivorous freshwater catfish

Samples of eggs, newly hatched larvae (NHL), and larvae at the end of the lecithotrophic period (eight days after hatching) (LPL) of Lophiosilurus alexandri were collected to determine the amino acid and fatty acid profiles. Crude protein did not change throughout initial development and the concentration of lipids was highest in NHL. The content of the indispensable amino acids (IAA) isoleucine, leucine, and valine decreased in LPL, while in eggs and NHL they remained high and similar in value. The dispensable amino acids (DAA), such as aspartic acid, tyrosine, and glycine, increased in LPL, while alanine decreased. The percentage of neutral lipids increased in LPL. The saturated fatty acid content decreased during ontogeny, while monounsaturated fatty acids decreased only in LPL. The polyunsaturated fatty acid content was highest in LP. Polar fatty acids were found in higher percentages in eggs and NHL, but lower in LPL. Saturated fatty acid content decreased during ontogenetic development, while that of monounsaturated fatty acids decreased only in LPL. Polyunsaturated fatty acid content was highest in LPL. Protein content was maintained during ontogenetic development, while amino acid classes experienced changes. Lophiosilurus alexandri preferentially uses saturated and monosaturated fatty acids as an energy source during its early development.(AU)

Larvicultura do betta em água levemente salinizada

1Universidade do Estado de Santa Catarina, Avenida Luis de Camões, 2090, 88520-000, Lages, SC, Brasil, thiagofabregat@hotmail. com (autor correspondente) 2Fundação Instituto de Pesca do Estado do Rio de Janeiro, Laboratório de Reprodução de Peixes Nativos e Exóticos. Cordeiro, RJ, Brazil. Cep 28540-000. 3Universidade Federal de Minas Gerais, Escola de Veterinária, Laboratório de Aquacultura, CEP 567, 30123-970, Belo Horizonte, MG, Brazil. 4Universidade Estadual Paulista, Centro de Aquicultura, 14884-900 Jaboticabal, SP, Brazil. ABSTRACT

The effect of water temperature on muscle cellularity and gill tissue of larval and juvenile Lophiosilurus alexandri, a Neotropical freshwater fish

The effect of temperature on muscle development and gill tissue were investigated in larval and juvenile of Lophiosilurus alexandri, a carnivorous Neotropical fish species. Larvae and juveniles were reared at temperatures of 23, 26, 29 and 32 °C for 15 and 35 days, respectively. The larvae were fed Artemia nauplii, while the juveniles received a formulated diet. In both stages, high temperatures resulted in increased fiber diameter of white muscle. Moreover, a pronounced effect of hypertrophy was observed in later stages of development. No alterations to minimum fiber diameter, and similar mosaic standards of muscle growth dynamics, were observed in larvae kept at 23-32 °C, suggesting that hyperplasia was not effected during early stages of development. Gills were analyzed by Degree of Tissue Change (DTC), which is based on the severity of lesions. Significant morphological changes were observed in gills when juveniles were kept at 32 °C, which was considered moderate tissue damage. Temperature modulates cellularity in L. alexandri larvae and juveniles, with pronounced alterations of hypertrophy of white muscle fibers in later stages of development when exposed to elevated temperatures. Higher temperatures may also induce muscle growth dynamics with increased recruitment of new white fiber, increased fiber diameter in the early stages and induced gill lesions.

Períodos de condicionamento alimentar de juvenis de pirarucu na transição da alimentação de ração úmida para seca

The objective of this work was to evaluate the effect of feed training periods on the productive performance and survivorship of pirarucu juveniles ( Arapaima gigas ), during the transition from ground fish mass diet to a dry-feed diet. Animals with 15.8±1.2 g were evaluated with gradual substitutions of the diet at every 2, 3, 4, and 5 days. After 12 days from feed training, the substitutions at every two and three days provided the highest specific growth rates. The replacement of diet based on forage fish by dry formulated diet may be done every two or three days.