Anaesthetics are important in ¢sh culture to reduce handling stress and mortality. Eugenol is a promising anaesthetic because of its low cost, e⁄cacy, safety margin for ¢sh and lack of toxicity to humans. The goal of this study was to establish a protocol using eugenol as a ¢sh anaesthetic for tambaqui Colossoma macropomum (Cuvier), and provide information for regulating authorities on establishing safety dosage protocols for its use. Juvenile and sub-adult tambaqui were ¢rst individually exposed to doses of 35, 50, 65, 85, 100 or 135 mg L À 1 eugenol for 10 min. A second experiment examined the e¡ect of the duration of exposure to eugenol on the time required for recovery and survival of tambaqui. A eugenol dose of 65 mg L À1 was adequate to induce ¢sh of both sizes into a surgical anaesthetic state, and recovery time was similar for dosages up to 100 mg L À1 . Exposure to the ideal dose (65 mg L À 1 ) for up to 30 min did not cause ¢sh mortality. Fish blood glucose values were similar for all the tested eugenol doses as well as with the benzocaine control. The results show that eugenol is an e⁄cient and safe anaesthetic for tambaqui.

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Abstract.— The present study investigated the use of benzocaine as an anesthetic for juvenile Colossoma macropomum (tambaqui). In the first experiment, fish were exposed to various doses of benzocaine for 10 min at 24 C. The second experiment examined the effects of duration of exposure to 100 mg/L of benzocaine. In the third experiment, fish were exposed to 100 mg/L at temperatures of 24, 27, and 30 C. Benzocaine concentrations of 100–150 mg/L were considered ideal for quickly inducing total immobilization and fast recovery. Fish exposed to 350 mg/L benzocaine exhibited 30% mortality. No changes in hemat‐ocrit were recorded in fish exposed to different concentrations of benzocaine. Plasma glucose increased significantly when fish were exposed to benzocaine concentrations greater than 200 mg/L. Recovery time after a 30‐min exposure to 100 mg/L benzocaine was significantly greater than after an exposure for 10 and 20 min. No mortality was observed 96 h after exposure to 100 mg/L benzocaine for 10, 20, and 30 min. Dosages in the 100–150 mg/L range were effective for periods of up to 20 min of anesthesia. There was no effect of temperature on the time required for fish to lose equilibrium. However, recovery was significantly faster for fish anesthetized at 30 C. Benzocaine is an effective anesthetic agent for tambaqui juveniles, providing rapid immobilization and rapid recovery. Benzocaine is also less expensive than other available anesthetic compounds.

The increased demand for juvenile tambaqui Colossoma macropomum for grow‐out ponds and stocking programs in the Amazon state of Brazil has increased the transportation of this species. This study was designed to determine the optimum density of juvenile tambaqui during transportation in closed containers. Fish (51.9 ± 3.3 g and 14.9 ± 0.4 cm) were packed in sealed plastic bags and transported for 10 h at four densities: 78, 156, 234, and 312 kg/m3. After transportation, fish from each density were kept in separate 500‐L tanks for 96 h. Mortality, 96‐h cumulative mortality, water quality, and blood parameters (hematocrit, plasma cortisol, and glucose) were monitored. Fish mortality after transportation was significantly lower at densities of 78 and 156 kg/m3 than at 234 and 312 kg/m3. Cumulative mortality was significantly lower at a density of 78 kg/m3. Dissolved oxygen after 10 h of transportation remained high at a density of 78 kg/m3, but reached critically low values at all other densities. Ammonia concentration was highest at the lowest density and was lower at higher densities. Carbon dioxide concentration was lowest at the density of 78 kg/m3 but higher in the other treatments. Plasma glucose and cortisol increased significantly immediately after transportation at densities of 156, 234, and 312 kg/m3, returning to control values by 24 h. The best density for juvenile tambaqui during a 10‐h transportation haul in a closed container was 78 kg/m3. At this density there was no fish mortality, water quality was kept within acceptable values, and fish were not stressed.

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Resumo -Os objetivos deste trabalho foram testar a eficiência do sal como redutor de estresse e verificar a melhor densidade de transporte de juvenis de tambaqui (Colossoma macropomun) em caixas de plástico adaptadas. No primeiro experimento foram testadas diferentes concentrações de sal de cozinha (NaCl) na água; no segundo, o transporte foi realizado por três horas em caixas de plástico de 200 L estocadas com diferentes densidades de peixe, com 8 g de sal/L de água. O cortisol plasmático dos peixes sofreu aumento significativo após o transporte no tratamento sem sal e com 2 g de sal/L de água, retornando para níveis normais após 96 horas. A glicose plasmática dos peixes sofreu aumento após o transporte em todas as concentrações de sal testadas, com exceção da com 8 g/L de água, retornando para níveis normais em 24 horas. Nos peixes transportados no segundo experimento, com 8 g de sal/L de água, não foi verificada mudança significativa no cortisol plasmático, mas a glicose aumentou significativamente em todas as densidades após o transporte, retornando para níveis normais em 24 horas. Houve mortalidade de 11% em uma das repetições da densidade de 200 kg/m 3 de água. Para o transporte com 8 g de sal/L de água, a densidade máxima deve ser de 150 kg/m 3 de água. Nesta densidade os parâmetros físico-químicos de qualidade de água se mantêm com características adequadas, as respostas ao estresse são mínimas e não há mortalidade.Termos para indexação: Colossoma macropomum, glicose, cloreto de sódio, cortisol, piscicultura. Assessment on the effect of salt and density on tambaqui fish transportationAbstract -The objectives of this study were to evaluate the efficiency of salt as a stress reductor and to determine the best transportation density for tambaqui (Colossoma macropomum) juveniles in customized plastic boxes. In the first experiment different concentrations of cooking salt (NaCl) in the water were tested, and in the second experiment the fishes were transported for three hours in 200 L plastic boxes using different fish densities and 8 g of salt/L of water. Plasma cortisol presented a significant increase after transportation in water without salt or with 2 g of salt/L, returning to normal levels after 96 hours. The fishes exposed to all salt concentrations had plasma glucose increased after transportation, except the treatment with 8 g of salt/L of water, returning to normal levels within 24 hours. In the second experiment, the fishes transported at different densities with 8 g of salt/L of water did not present a significant change in plasma cortisol after transportation, but plasma glucose increased after transportation at all fish densities, returning to normal levels in 24 hours. Fish transported at a density of 200 kg/m 3 of water had 11% mortality in one of the replicates. For tambaqui transportation with 8 g of salt/L of water, maximum density should be 150 kg/m 3 of water. At this density water parameter levels are adequate, stress responses are minimum and there is no fish mortality.

The Brazilian Government has been promoting studies on the zoning and demarcation of aquaculture parks dedicated to the production of fish in net-cages in the large public reservoirs of the country. The methodology employed for the zoning of these aquaculture parks consists of the execution in three consecutive stages of multidisciplinary evaluations for their social, environmental and economical characterization (global, regional and local). The purpose of the studies involves the generation of thematic maps and scenarios of environmental models that facilitate the process of understanding the regional peculiarities and taking the decisions to identify the most appropriate areas for the installation of the aquaculture parks. The application of this instrument for zoning the reservoirs will assist a more effective planning of investments and efforts, both by the government and by private initiative, in the aquaculture activity. With the implantation of aquaculture parks along the lines of an ecosystemic aquaculture, Brazil has the potential to become one of the largest producers of fish in net-cages in the world.

Tambaqui Colossoma macropomum (Cuvier) is a ¢sh of primary importance in Amazon aquaculture. It has been described as an acid-resistant species that moves seasonally between white (muddy) water and black water rivers and enters the extremely dilute acidic areas of £ooded jungle to feed during the rainy season. To analyse the pH tolerance of this species, tambaqui were exposed to three water pH levels for 40 days (pH 4.0, 6.0 and 8.0). The water was acidi¢ed slowly over 3 h, allowing the ¢sh to acclimate. A similar protocol was used to adjust water pH to 8.0. No mortality was observed during the exposure period. Several haematological parameters were signi¢cantly changed in alkaline-exposed animals, with signi¢cant decreases in haematocrit (20%), haemoglobin concentration (8%) and red blood cells (12%). Tambaqui showed severe blood variations when exposed to alkaline pH. Fish ¢nal weight, condition factor and speci¢c growth rate (SGR) was inversely proportional to a pH increase, and SGR were higher for ¢sh reared in acidic water. The relative insensitivity of tambaqui to low pH con¢rms its acid tolerance and is in accordance with its natural occurrence in black water habitats.