Optimum loading density for the transport of matrinxã juveniles was investigated in a closed system with plastic bags. Transport was conducted for 4 h with fish (23.5± 0.4g and 11.6 (0.08cm)

Respostas fisiológicas de estresse no matrinxã (Brycon amazonicus) após exercício físico intenso durante a captura Physiological stress responses of matrinxã (Brycon amazonicus) after chasing ABSTRACTThis study reports the stress responses of matrinxã after chasing. Juvenile fish (26.7±6.7 g) were adapted to 100L plastic boxes and submitted to the treatments: Control (no chasing), Chasing for 2 min, Chasing for 5 min, Chasing for 10 min (four boxes/ treatment, 32 fish). Blood was drawn 15, 30 and 60 min after chasing to determine levels of cortisol, glucose, sodium, chloride, potassium, calcium, hematocrit, hemoglobin, erythrocytes number and osmolality. Matrinxã responses after forced swimming did not show the typical stress responses. There were no changes in blood cortisol, glucose, potassium and calcium levels in fish from any treatment until 60 min after chasing. Blood chloride levels were lower 15 min after chasing while the lowest levels of sodium were registered 60 min after the forced swimming. Osmolality dropped 30min after chasing, regardless the period of chasing. The intense swimming did not affect hematological indicators confirming the other physiological indicators.The results suggest that the intense swimming provoked by chasing up to 10 min was not intense enough to promote stress responses in matrinxã indicating that the species is very resistant to the farming handling.

This study compared the larval performance of matrinxa ì , Brycon amazonicus, after maternal triiodothyronine (T 3 ) injection or egg immersion of T 3 . In the ¢rst experiment, three groups of females (n 5 4) induced to spawning received pituitary extract (CPE) and a corn oil injection (control), or CPE plus 10 mg or 20 mg kg À 1 bw T 3 dissolved in corn oil (experimental). Larvae were sampled for body weight and length measurement at hatching (0 h) and12, 24, 36, 48 and 60 h thereafter. Hatching time, hatching success and abnormal development were monitored. In the second experiment, fertilized eggs from four females were immersed inT 3 solutions (0,0.01,0.05 and 0.10 mg L À 1 ) and larvae were sampled at hatching (0 h) and 6, 18, 30, 42, 54, 126 and 198 h thereafter. Hatching time was not a¡ected by either means of hormone treatment. Abnormalities decreased as the T 3 concentration increased in larvae from T 3 -treated brood¢sh but the number of dead larvae increased proportionally. Larvae from T 3 -injected females had higher weight from 24 h after hatching and greater length from hatching, while the weight of larvae produced from T 3 -immersed eggs changed at 198 h and length from 126 h of rearing. Both routes of T 3 administration a¡ected the early growth of matrinxa ì but the e¡ect was observed earlier when broodstock females were injected.

Brazilian fish farms presented an accelerated development during the early 90's, mainly because of the increase in fee-fishing operations. To meet the demand of this market, fish production and supply became excessive and, as a consequence, the number of fee-fishing operations, farmers and the final selling price, decreased. This study analyzes the technical aspects, production cost, profitability and economic viability of the production of piauçu (L. macrocephalus) in ponds, based on information from a rural property. Feeding and fingerling costs amount to approximately 47.1% of the total production cost, representing together with the final selling price the most important factor affecting profitability. The payback period was 8.3 years, the liquid present value US$ 291.07, the internal return margin 9%, and the income-outcome ratio was 1.01, which represents an unattractive investment as a projection based on current conditions. The improvement in productive efficiency enhances the economic valuation index, and that the relative magnitude of cost and income are the most important points for the economic viability of the studied farm. Key words: costs, profitability, economic analysis, sensitivity analyses, fish farming VIABILIDADE ECONÔMICA DA PRODUÇÃO DE PIAUÇU Leporinus macrocephalus (Garavello & Britski, 1988)RESUMO: A piscicultura brasileira apresentou um acelerado desenvolvimento nos anos 90, principalmente impulsionada pelo aumento de estabelecimentos pesqueiros conhecidos como "pesque-pagues". Entretanto, o aumento do número de criadores de alevinos e a redução de pesqueiros resultou em um aumento na oferta de peixes e, conseqüente, diminuição do preço de comercialização. O presente estudo analisa os parâmetros zootécnicos, os custos de produção, a rentabilidade e a viabilidade econômica da engorda de piauçu (L. macrocephalus) em tanques escavados. Os custos com insumos somam 47,1% do custo total de produção, representando juntamente com o preço de venda do pescado, o fator decisivo na rentabilidade da atividade. O período de recuperação do capital foi de 8,3 anos, valor presente líquido de US$ 291,07, taxa interna de retorno de 9% e relação benefício-custo de 1,01. Como projeto, nas condições atuais, trata-se de um investimento de baixa atratividade. O aumento da eficiência produtiva melhorou os índices de avaliação econômica e o acompanhamento dos custos e receitas é ponto fundamental para a viabilidade econômica da propriedade estudada. Palavras-chave: custo de produção, rentabilidade, análise econômica, análise de sensibilidade, piscicultura