Ronald Kennedy Luz

Larvicultura do Mandi-amarelo Pimelodus maculatus Lacépède, 1803 (Siluriformes: Pimelodidae) em Diferentes Densidades de Estocagem nos Primeiros Dias de Vida

The effect of stocking density on the larviculture of Pimelodus maculatus post-larvae was evaluated. The experiment was conducted at the Sao Carlos hatchery (EPISCar), SC. Post-larvae were daily fed zooplankton at the rate of 300 organisms/post-larvae/day at the following densities: T1. 5 post-larvae/L; T2. 15 post-larvae/L; and T3. 30 post-larvae/L. Survival rates were evaluated on the third and fifth day of the experiment. After three days, density did not affect survival rates; however, on the fifth day survival rate was higher for the lowest density. Average survival rates at the end of the experiment were 35.6, 28.9 and 20.6% for T1, T2 and T3, respectively. Post-larvae average weight was also higher at the lowest density, but average length did not differ significantly among treatments. At density of 30 post-larvae/L, post-larvae survival rate was the lowest, but final productivity was the highest.

Condicionamento alimentar de alevinos de trairão (Hoplias cf. lacerdae)

An evaluation of training strategies in fingerlings of trairao was carried out. The experimental design included six 20 L tanks with artificial aeration, controlled temperature variation (27±0.5oC), and continuously darkened (0L:24D), except during daily management. Fingerlings with 2.9±0.2 cm long were kept at a 4 specimens/L and they were allotted to the following treatments: the first was direct offering of artificial diet and the second involved training strategies by means of the replacement of semi humid food for dry food. At the end of the experiment, average survival rates were 27.5 and 96.66% for the first and second treatments, respectively, demonstrating that feeding conditioning is an efficient management in production and survival of Hoplias cf. lacerdae fingerlings.

Freqüência Alimentar na Larvicultura do Trairão (Hoplias lacerdae)

The effects of feeding management strategies on larval rearing of trairao were evaluated in this trial. Eight-d old larvae were counted and stocked in 20 experimental containers (units with volume of 5 L each), with constant aeration and temperature. The stocking density was 30 larvae/L. The following treatments (feeding frequency) were used: F1 - once a day, F2 - twice a day, F3 - three times a day, F4 - four times a day, each with five replicates. Feeding rate was equal for all treatments. In order to evaluate the animal growth, some samples were collected every five days. At the end of the experiment, after 23 days, the survival, mortality, rates of cannibalism and stress resistance were also evaluated. No significant difference was observed among the growth parameters at 13 days. However, after 18 and 23 days, F1 treatment showed the lowest length and weight averages. No differences of larval specific growth rate due to the feeding frequencies were observed. No effects of feeding frequency on rates of survival, mortality, cannibalism and stress resistance were detected. The survival rates showed the highest values (93%) during the experiment. Thus, trairao larvae can be fed only twice a day, with no changes on growth, at least during the initial rearing (first 23 days).

Diferentes densidades de estocagem na produção de alevinos de trairão (Hoplias cf. lacerdae)

Alevinos de trairao (Hoplias cf. lacerdae), com peso e comprimento total medios de 12,52 g e 10,5 cm, respectivamente, previamente condicionados ao aceite de dietas artificiais, foram distribuidos em seis tanques de alvenaria (5m²) nas densidades de: 1 e 4 alevinos/m². Os peixes dos diferentes tratamentos foram alimentados ad libitum nos horarios de 8 e 14 h com racao comercial extrusada contendo 42% de proteina bruta. A cada trinta dias realizou-se a troca do volume total de agua de todos os tanques. Ao final do experimento (120 dias) foi avaliado o desempenho produtivo dos peixes, por meio da taxa de sobrevivencia, conversao alimentar, ganhos em comprimento e em peso diario. Foram observadas taxas medias de sobrevivencia de 86,7 e 96,7% para as densidades de 1 e 4 peixes/m², respectivamente. A conversao alimentar foi de 1,6 e 1,2; o ganho em peso diario e em comprimento de 0,70 e 0,38 g e 8,01 e 7,27 cm, respectivamente. Estes valores nao diferiram entre si. Com os resultados obtidos pode-se concluir que as densidades de estocagem de 1 e 4 peixes/m² podem ser utilizadas no cultivo de alevinos de trairao sem que haja comprometimento no seu desempenho produtivo.

Tolerance to the Air Exposition Test of Hoplias lacerdae Larvae and Juvenile during Its Initial Development

ABSTRACT The establishment of evaluation parameters for larvae and juvenile quality assessment is highly desirable . Theexperiment evaluated the Stress Resistance Rate (Re) on Hoplias lacerdae tlarvae and juveniles. Larvae on the 13h,16 th , 19 th , 23 rd and 26 th days of life were subjected to Re evaluation tests. Twenty animals were stoked in one literbeaker and kept at 27 to 28.5°C. The following treatments were applied: E 3 -3 minutes; E 5 - 5 minutes; E 7 - 7minutes; E 10 - 10 minutes and E 15 -15 minutes on drying paper. After 24 hours Re was evaluated. It was observedthat Re values showed an increase from 13 th to 19 th day in all treatments indicating an increasing resistance relatedto larval development. High Re rates were observed during the whole experiment, with the lowest value (P<0.05)found on treatment E 10 (67.7% on the 13 th day) and E 15 (41.25% on the 26 th day). It could be concluded that trairaolarvae and juvenile were resistant to the air exposition test on drying paper and expositions higher than sevenminutes were more efficient for Re evaluation of trairao larvae and juveniles subjected to different rearingconditions.Key words: Hoplias lacerdae, fish larvae, stress resistance

Capture, adaptation and artificial control of reproduction of Lophiosilurus alexandri: A carnivorous freshwater species.

The present study describes the capture adaptation and reproduction of wild Lophiosilurus alexandri broodstock in laboratory conditions. There were two periods when capturing was performed in natural habitats. The animals were placed in four tanks of 5m(3) with water temperatures at 28°C with two tanks having sand bottoms. Thirty days after the temperature increased (during the winter) the first spawning occurred naturally, but only in tanks with sand on the bottom. During the breeding season, there were 24 spawning bouts with egg mass collections occurring as a result of the spawning bouts that occurred in the tanks. The hatching rates for eggs varied from 0% to 95%. The spawning bouts were mainly at night and on weekends. In the second reproductive period, the animals were sexed by cannulation and distributed in four tanks with all animals being maintained in tanks with sand on the bottom at 28°C. During this phase, there were 36 spawning bouts. Findings in the present study contribute to the understanding of the reproductive biology of this endangered species during captivity.

Salinity and temperature variations reflecting on cellular PCNA, IGF-I and II expressions, body growth and muscle cellularity of a freshwater fish larvae

The present study assessed the influence of salinity and temperature on body growth and on muscle cellularity of Lophiosilurus alexaxdri vitelinic larvae. Slightly salted environments negatively influenced body growth of freshwater fish larvae and we observed that those conditions notably act as an environmental influencer on muscle growth and on local expression of hypertrophia and hypeplasia markers (IGFs and PCNA). Furthermore, we could see that salinity tolerance for NaCl 4gl(-)(1) diminishes with increasing temperature, evidenced by variation in body and muscle growth, and by irregular morphology of the lateral skeletal muscle of larvae. We saw that an increase of both PCNA and autocrine IGF-II are correlated to an increase in fibre numbers and fibre diameter as the temperature increases and salinity diminishes. On the other hand, autocrine IGF-I follows the opposite way to the other biological parameters assessed, increasing as salinity increases and temperature diminishes, showing that this protein did not participate in muscle cellularity, but participating in molecular/cellular repair. Therefore, slightly salted environments may provide adverse conditions that cause some obstacles to somatic growth of this species, suggesting some osmotic expenditure with a salinity increment.

Feed training of juvenile giant trahira under different light intensities

The aim of this study was to evaluate the influence of light intensity on the feed training of juvenile giant trahiras (Hoplias lacerdae). A completely randomized design with four light treatments and three replicates was used, and the following light intensities were tested: 204.9; 177.58; 54.64 and 0.00 lux. Juvenile giant trahiras (length = 3.0 ± 0.4 cm and weight = 0.5 ± 0.05 g) were stocked at 6 fish L-1 in 12 rectangular tanks (24 × 20 × 14 cm) containing six liters of water, and subjected to feed training to accept dry diets. At the end of the experiment (21 days), weight gain, length gain, survival, cannibalism, and mortality rates were evaluated. Data were subjected to regression analysis at 5% probability. Different light intensities did not affect growth, survival, mortality, or cannibalism rates in juvenile giant trahiras during the feed training. Therefore, this species can be trained to accept dry diets in the presence or absence of light.

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