Dwarf rainbowfish (Melanotaenia praecox) are an ornamental fish with a high added value and considerable commercial interest. However, little information is known about the organism's reproductive biology, especially the early stages of embryonic development (initial ontogeny). Melanotaenia praecox embryos were examined throughout development to describe the dwarf rainbowfish initial ontogeny. Eggs were incubated at 28°C, and observations were recorded at pre-determined times. Development stages were identified and classified according to morphophysiological characteristics. The initial size of the eggs ranged between 0.99 and 1.04 mm. Oil droplets were observed in the eggs, and fixing filaments for adhesion were observed in the corium. Embryonic development was similar to that of other species in the genus Melanotaenia, in which hatching begins 119.50 h post-fertilisation or 3405.75 degree-h post-fertilisation. The main features of the newly hatched larvae were excellent swimming activity, a reduced yolk sac, mouth movement and an apparently functional digestive system.

RESUMOConduziu-se um experimento com o objetivo de avaliar a influência do período de coalimentação na sobrevivência e no crescimento de larvas de Betta splendens. As larvas foram alimentadas com náuplios de Artemia durante sete dias e, posteriormente, submetidas aos seguintes tratamentos: jejum contínuo; ração contínua; quatro dias de coalimentação + 14 dias de ração; oito dias de coalimentação + 10 dias de ração; 12 dias de coalimentação + seis dias de ração; náuplios de Artemia durante todo o período experimental. Os valores das variáveis de desempenho das larvas do tratamento 12 dias de coalimentação + seis dias de ração e do tratamento náuplios de Artemia foram superiores aos demais tratamentos, exceto para sobrevivência, em que não houve diferença significativa com o tratamento oito dias de coalimentação + 10 dias de ração. Considerando-se apenas o tempo de oferta de Artemia (em dias), obteve-se a equação de regressão para as variáveis analisadas. A sobrevivência e a taxa de crescimento específico (TCE) apresentaram efeito quadrático, e as demais variáveis apresentaram efeito linear. O ponto de máxima para sobrevivência foi de 21,7 dias (88,92%) e para TCE foi de 26,2 dias (23,47% dia -1 ). O período de co-feeding influencia no crescimento e na sobrevivência de larvas de Betta splendens. Após o período de 19 dias de oferta de alimento vivo, com 12 dias de coalimentação, as larvas estão aptas a aproveitar de maneira eficiente o alimento inerte sem prejuízos ao crescimento e à sobrevivência.Palavras-chave: peixes ornamentais, Betta splendens, larvicultura de peixes, coalimentação, transição alimentar ABSTRACT An experiment was carried out to evaluate the influence of the period of co-feeding on survival and growth of Betta splendens larvae. The following strategies for co-feeding were used: continuous fasting, 18 days of inert diet, 4 days of co-feeding + 14 days of inert diet; 8 days of co-feeding + 10 days of inert diet; 12 days of co-feeding + 6 days of inert diet, nauplii of Artemia throughout the experiment period. The values of performance variables for larvae with 12 days of treatment for co-feeding + 6 days of inert diet and the nauplii treatment with

We tested the effect of fasting on the development of juvenile freshwater angelfish (Pterophyllum scalare). The juveniles were subjected to different fasting periods (0, 3, 6, 9, 12, and 15 days of fasting). Fish from all treatments were fed for 30 days after the fasting period. No difference (P > 0.05) was observed between treatments for final weight and length. There was a significant difference (P < 0.05) in treatments 12 and 15 days fasting for liver and intestine weight. These results may prove that 12 and 15 days of fasting force juveniles to use energy reserves, and these adaptations may also represent a saving energy strategy. The fish subjected to treatments 6, 9, 12, and 15 days of fasting showed different vacuolization in hepatocytes from the ones subjected to 0 and 3 days of fasting (P < 0.05). These results show that during the lack of feeding, juveniles (P. scalare) mobilizes energy stored in the liver. No difference (P > 0.05) was observed between treatments for survival rate. However, the increase in the number of deaths from the eighth day of fasting may indicate that periods with more than 15 days of fasting could be fatal to this species during this life stage. According to our findings, it can be assumed that juvenile freshwater angelfishes have strategies (e.g. a decrease in liver and intestine weight) to resist 15 days of fasting.

Three experiments were done with different particle sizes of corn feed on its zootechnical performance, passing rate and apparent digestibility of juvenile tambaqui (Colossoma macropomum). In the first, 200 juveniles were used and distributed in 20 tanks (220 L), 10 fish per unit (four replicates). The experimental system used to record passage time was composed of five incubators with 200 L. In the second, 75 juveniles were used per 55 days (three replications). In the third, 75 juveniles were used and distributed in five incubators of 200 L. All experiments were performed randomly. Different linear behavior treatments were observed for apparent digestibility of crude protein; and the smaller particle size (150 μm) had better results digestibility. smaller particle size of the corn had better results, affected the growth performance of tambaqui and the apparent digestibility of crude protein and ether extract. Thus, is recommended that a particle size of 150 μm of corn be used for tambaqui.

Aim of study: to analyse the effect of stocking density on common carp larvae production. Since stocking density is one of the most important variables in recirculating aquaculture system, it is fundamental to understand its implication on fish larval development. Area of study: BrazilMaterial and methods: In an initial trial over a 30-day period, 18,000 Cyprinus carpio larvae were subjected to eight different stocking densities (5, 10, 15, 20, 25, 30, 35 and 40 larvae/L). In a second trial over a 15-day period, the larvae subjected to the 40 larvae/L treatment were selected according to size and 360 of them were subjected to restocking processes at a density of 5 larvae/L, in order to evaluate possible compensatory growth, while those subjected to the 5 larvae/L treatment were likewise selected according to size and were distributed at the same stocking density (5 larvae/L), to be the control treatment during the restocking process.Main results: The larvae kept at the density of 5 larvae/L showed better growth and development. Increased heterogeneity of the concomitant batch was observed with higher stocking density. Restocking at low density (5 larvae/L), for larvae that had previously been kept at high density (40 larvae/L), caused partial compensatory growth, with an increase in the specific growth rate. Increasing the density caused increased productivity up to the density level of 25 larvae/L, but from then on there was no significant difference (p > 0.05).Research highlights: Carp larvae reared at high densities need to be restocked during rearing in order to avoid the “shooting” problem.

This study aimed to evaluate the influence propolis extract inclusion to the feed mixture for juvenile angelfish (Pterophyllum scalare) on larval performance and transport. Levels of propolis extract inclusion consisted of 0, 300, 600, 900, and 1200 mg.kg -1 of feed. After 14 days of hatching, unmetamorphosed larvae with a total length of 18.4 mm and 0.11 g initial weight were used. Six-hundred larvae were divided into 20 experimental units, totalizing 30 larvae each. Experimental units consisted of polythene containers with independent water input and output and a level controller. Each unit was controlled for maintenance of 40 L water within a recirculation system. After offering feed containing propolis extract, five fish from each experimental unit were packed in bags for transportation only with atmospheric air, without pure oxygen addition. The bags were filled with 300 mL water on a 2:1 basis of air and water respectively. The total transport time was considered until the death of the third fish in package. At the end of the experiment, data underwent statistical analysis through Statistical Analysis System (SAS, 2001). Results showed there was no significant difference (P<0.05) neither for any of the studied zootechnical variables (standard length, total length, height, and weight) nor for the transport of juveniles. In conclusion, propolis extract addition to angelfish feed was ineffective for larval performance and for transportation of juveniles, at the levels tested here.

Four treatments were established to evaluate the effect of delayed first exogenous feeding and subsequent feeding periods on the development of goldfish larvae. The fasting and feeding periods were arranged as follows: T1 (0DFA:30DF), T2 (4DFA:26DF), T3 (8DFA:22DF), and T4 (12DFA:18DF), where DFA are the days of fasting and DF are the days of feeding. The larvae were kept in community tanks for each repetition, with 75 larvae per tank (3.75 larvae L-1). There was no significant difference in total length or final weight between larvae submitted to 0, 4, and 8 days of feed deprivation. However, larvae submitted to 12 DFA had higher values of the same variables than the other treatments. No significant difference in larval survival was observed between T1, T2, and T3, but T4 negatively influenced survival. Under the conditions evaluated, the point of no return was 4 DFA. Dead larvae were partly eaten in the fasting treatments. The delayed first feeding should be avoided in large-scale productions since it significantly reduces survival during cultivation. This article results from research funded by the Pescarte Environmental Education Project (PEA/IBAMA).

In order to optimize the performance and reduce costs in the larviculture of ornamental carp (Cyprinus carpio) in a recirculating aquaculture system, different feeding strategies were tested. For this, two experiments were carried out both under controlled conditions in a greenhouse, in a recirculating aquaculture system with a physical particle filter, biofilter, and filtering by ultra-violet irradiation. In the first experiment, measurements of Artemia nauplii were tested in the initial exogenous feeding of larvae at concentrations of 100, 200, 400, 600, 800 and 1,000 Artemia nauplii per larvae. In the following experiment, different protocols were tested for initial feeding for larvae. At this stage, were used: live food (Artemia nauplii) and inert (powder meal), used separately and simultaneously, and increases in the number of Artemia nauplii were also tested, offered at different times of cultivation. In the first experiment, the amount of 600 Artemia nauplii for larvae demonstrated to be the best option as it generated significant growth and the cost was less than that observed with the use of 800 and 1000 Artemia nauplii per larvae. The second experiment demonstrated that the feeding strategy with live food more commercial inert feed provided the best growth performance for ornamental carp larvae. The need to fix the amount of live food during the cultivation, probably due to the high specific growth rates observed during the larval stage also became evident.