22 research outputs found
Effects of delayed first feeding on growth of the silver catfish larvae Rhamdia voulezi (Siluriformes: Heptapteridae)
ABSTRACT The effects of the timing of first feeding on the point-of-no-return (PNR) and growth of laboratory reared silver catfish Rhamdia voulezi larvae were studied. The experiment began immediately after the complete absorption of the yolk sac, 3 days after hatching (DAH). The food was provided for the first time on 3rd, 4th, 5th, 6th, 7th, 8th, and 9th DAH. Zooplankton and newly-hatched Artemia spp. were used to feed the larvae. To evaluate the effect of food deprivation on growth, the standard length and weight of 594 larvae were assessed. Larval growth was significantly affected by the time of first exogenous feeding. The larvae fed from 3rd to 5th DAH showed a significantly higher development than those fed from 6th DAH. The larvae reached the PNR on 6th DAH. Survival and larval growth strongly depended on the timing of initial feeding. In order to avoid potential mortality by starvation and obtain good growth, the silver catfish larvae R. voulezi must establish successful initial feeding within 5 days after hatching
Recommended from our members
Session A8: Fishway Permeability for Two Neotropical Long Distance Migratory Species
Abstract:
The effectiveness of fishways should consider the senses of fish movements, both downstream and upstream, if we really want to have them as a tool to minimize the dam impacts. In this study we evaluated the effectiveness of the fishway of the Hydropower Plant “Engenheiro Sergio Motta” (Porto Primavera dam), Upper Paraná River, southeastern Brazil, during 627 days between December, 2012 and August, 2014. We tagged 995 fish with PITtags 23mm, distributed in 628 Prochilodus lineatus and 367 Leporinus obtusidens. The fish were released both downstream (416 P. lineatus and 58 L. obtusidens) and upstream of the dam (212 P. lineatus and 309 L. obtusidens). A total of 145 (34.8%) P. lineatus tagged downstream concluded the passage and 25 (17.2%) of those passed back. The average time of the upstream movement were 201.4 days, with a minimum of 01h 07min and a maximum of 448 days. Of the 58 L. obtusidens released in downstream, 19 individuals (32.8%) ascent the fishway and of these there were no subsequent downstream movements. From 212 P. lineatus tagged upstream, 34 (16%) descent the fishway, with a mean of 148.8 days, minimum of 1hr 54min and maximum of 421.5 days. As for the 309 L. obtusidens released upstream, 21 individuals (6.8%) descent the fishway, with average time spent 36.6 days, the minimum and maximum time was, respectively, 7.6 and 448 days. The permeability of fish ladder is essential for maintenance of migratory species, especially long distance, providing connectivity between different areas of life (feeding and breeding), in order to maintain the fitness of these target species and its consequent conservation
Characterization of the early development of Pseudoplatystoma reticulatum Eigenmann & Eigenmann, 1889 (Siluriformes: Pimelodidae) from the Paraguay River Basin
ABSTRACT This study described the initial development of Pseudoplatystoma reticulatum, as well as changes in growth patterns. Morphometric and meristic variables were analyzed during embryonic, larval and juvenile periods, even as allometric growth coefficients for larvae and juveniles. Eggs showed an average diameter of 1.79 mm and broad perivitelline space (23.41%). The total length (TL) of the larvae ranged from 3.05 to 25.72 mm, and the total number of myomeres ranged from 45 to 50 (preanal = 13-16 and postanal = 30-35). Initial pigmentation is poor, concentrated at the extremities of the yolk sac. In the flexion stage, the pigmentation intensifies and forms a longitudinal stripe extending from the snout to the operculum and two longitudinal stripes on the body, one dorsal and the other ventral, that unite at the caudal peduncle. At first, there is a differential growth of the head and tail, and then there is the growth of the body, which shows changes in the ontogenetic priorities of feeding, swimming, and breathing capacities. Our results are very important for ecology, systematics, and hatchering, especially in terms of ontogenetic variation in morphology, growth, feeding, behavior, and mortality of P. reticulatum
Desenvolvimento embrionário, larval e juvenil de Hemisorubim platyrhynchos (Siluriformes, Pimelodidae) da bacia do rio Paraná
O objetivo deste estudo foi descrever o desenvolvimento embrionário, larval e juvenil da jurupoca, Hemisorubim platyrhynchos (Valenciennes, 1840), bem como as mudanças nos padrões de crescimento alométrico durante a ontogenia inicial da espécie. Um total de 90 ovos, 210 larvas e 24 juvenis provenientes de reprodução induzida foram analisados quanto a variáveis morfométricas e merísticas, além do coeficiente de crescimento alométrico em relação à cabeça, tronco e cauda durante o período larval e juvenil inicial. Os ovos apresentaram diâmetro médio de 1,74 mm, espaço perivitelino amplo (21,29%), com média de 0,37 mm, e diâmetro médio do vitelo de 1,08 mm. O comprimento padrão (CP) das larvas variou de 3,47 a 11,85 mm, com a maioria das medidas apresentando aumento proporcional ao longo do desenvolvimento. O número total de miômeros variou de 40 a 46 (pré-anal=15-17 e pós-anal=24-30). As larvas iniciais de H. platyrhynchos apresentam pigmentação na cabeça e na região ântero-ventral do corpo (anterior e posterior do saco vitelino). No estágio de pós-flexão, a pigmentação se intensifica, distribuindo-se na região dorsal da cabeça, formando uma faixa longitudinal que se estende do focinho ao opérculo, assim como uma faixa transversal, de um flanco a outro, passando pela região anterior da nadadeira dorsal, com máculas distribuídas ao longo do corpo nos juvenis (CP=19,5-49,09 mm). Nos primeiros estágios de desenvolvimento larval, a cabeça e a cauda crescem muito mais rapidamente do que o tronco, o que indica prioridades relacionadas à alimentação e natação, as quais posteriormente tendem à isometria, com um crescimento rápido do tronco nos juvenis iniciais