Water acidification causes death of marine ornamental fish (Perciformes: Pomacentridae) during transport: contributing to the conservation of wild populations

Pomacentridae is a common family in the aquarium fish trade. Most species are harvested from nature. Here we evaluate the following water parameters in the pomacentrid sergeant major, Abudefduf saxatilis (Linnaeus, 1758), to assess their stress level during a 24, 48, and 72 hours transport: dissolved oxygen (DO), total ammonia, and pH. In addition, we evaluated the following physiological parameters: plasma osmolality, muscle water content, blood glucose, and the enzyme activities of the branchial carbonic anhydrase (CA), the hepatic glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD). The mortality of fish measuring >6 cm total length was 22%, while no mortality was observed for fish measuring <6 cm. The pH of the water was significantly correlated with fish mortality, especially for the initial 24 hours of transport. Hypoxia after 24-48 hours also led to fish mortality, but build up ammonia was not a problem even after 72 hours. We suggest that a minimum water volume of 125 ml/g fish is necessary for safe and cost-effective transport of the sergeant major, preferably with <6 cm in total length.(AU)

Water acidification causes death of marine ornamental fish (Perciformes: Pomacentridae) during transport: contributing to the conservation of wild populations

Pomacentridae is a common family in the aquarium fish trade. Most species are harvested from nature. Here we evaluate the following water parameters in the pomacentrid sergeant major, Abudefduf saxatilis (Linnaeus, 1758), to assess their stress level during a 24, 48, and 72 hours transport: dissolved oxygen (DO), total ammonia, and pH. In addition, we evaluated the following physiological parameters: plasma osmolality, muscle water content, blood glucose, and the enzyme activities of the branchial carbonic anhydrase (CA), the hepatic glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD). The mortality of fish measuring >6 cm total length was 22%, while no mortality was observed for fish measuring <6 cm. The pH of the water was significantly correlated with fish mortality, especially for the initial 24 hours of transport. Hypoxia after 24-48 hours also led to fish mortality, but build up ammonia was not a problem even after 72 hours. We suggest that a minimum water volume of 125 ml/g fish is necessary for safe and cost-effective transport of the sergeant major, preferably with <6 cm in total length.

Effect of humic acid on survival, ionoregulation and hematology of the silver catfish, Rhamdia quelen (Siluriformes: Heptapteridae), exposed to different pHs

This study evaluates whether humic acid (HA; Aldrich) protects the silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), against exposure to acidic pH. Survival, levels of Na+, Cl- and K+ plasma, hematocrit, hemoglobin and erythrocyte morphometry were measured. Fish were exposed to 0, 10, 25 and 50 mg L 1 HA at four pH levels: 3.8, 4.0, 4.2 and 7.0 up to 96 hours. None of the fish exposed to pH 3.8 survived for 96 hours into the experiment, and survival of fish subjected to pH 4.0 decreased when HA concentration increased. Plasma Na+ levels decreased when pH was acidic, with no influence of HA, while Cl- levels declined at low pH with increased HA concentration. The levels of K+ at pH 4.0 and 4.2 increased without HA. Hematocrit and hemoglobin augmented under the effect of HA. At pH 4.0 and 4.2, erythrocytes of fish not exposed to HA were smaller, an effect that was partially offset by the presence of HA, since the values at pH 7.0 were higher. Although HA showed some positive effects changes in hematological and plasma K+ª in silver catfish caused by exposure to acidic pH, the overall findings suggest that HA does not protect this species against acidic pH because it increased mortality and Cl- loss at pH 4.0.

Effect of humic acid on survival, ionoregulation and hematology of the silver catfish, Rhamdia quelen (Siluriformes: Heptapteridae), exposed to different pHs

This study evaluates whether humic acid (HA; Aldrich) protects the silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), against exposure to acidic pH. Survival, levels of Na+, Cl- and K+ plasma, hematocrit, hemoglobin and erythrocyte morphometry were measured. Fish were exposed to 0, 10, 25 and 50 mg L 1 HA at four pH levels: 3.8, 4.0, 4.2 and 7.0 up to 96 hours. None of the fish exposed to pH 3.8 survived for 96 hours into the experiment, and survival of fish subjected to pH 4.0 decreased when HA concentration increased. Plasma Na+ levels decreased when pH was acidic, with no influence of HA, while Cl- levels declined at low pH with increased HA concentration. The levels of K+ at pH 4.0 and 4.2 increased without HA. Hematocrit and hemoglobin augmented under the effect of HA. At pH 4.0 and 4.2, erythrocytes of fish not exposed to HA were smaller, an effect that was partially offset by the presence of HA, since the values at pH 7.0 were higher. Although HA showed some positive effects changes in hematological and plasma K+ª in silver catfish caused by exposure to acidic pH, the overall findings suggest that HA does not protect this species against acidic pH because it increased mortality and Cl- loss at pH 4.0.(AU)

Growth performance of Nile tilapia, Oreochromis niloticus, fingerlings reared in Na2CO3 limed waters / Desempenho produtivo de alevinos de tilápia nilótica, Oreochromis niloticus, em aquários submetidos à calagem com Na2CO3

Current experiment was undertaken during 6 weeks with Nile tilapia, Oreochomis niloticus, fingerlings (1.28  0.03 g) to assess the effects of moderate Na2CO3 liming on water quality and fish growth performance. Twenty-four 25 L-aquaria, with 15 fish per aquarium, were used, of which twelve aquaria were placed in the lab’s indoor room and twelve in the outdoor area. Two types of water (clear or green) and three different water-quality managements (none, HCl acidification and Na2CO3 liming) were simultaneously evaluated in a 3 x 2 factorial design. Total ammonia, calcium hardness, pH and total alkalinity in the green water aquaria were significantly higher than rates in the clear water aquaria. Slight liming acid water with Na2CO3 did not produce any significant effect on its water calcium hardness. No significant differences between controls and the experimental group were observed for any growth variables. Lime rearing water with Na2CO3 has no significant effect on tilapia growth performance if the initial total alkalinity of water is higher than 20 mg CaCO3 L-1.

O presente estudo foi realizado por seis semanas com alevinos de tilápia do Nilo, Oreochromis niloticus (1,28 +/- 0,03 g), para avaliar os efeitos da calagem moderada da água de cultivo com Na2CO3 na qualidade da água e no desempenho produtivo dos peixes cultivados. Vinte e quatro aquários de polietileno de 25 L foram utilizados para manter os peixes experimentais (15 peixes por aquário). Doze aquários foram instalados na sala interna do laboratório e 12 aquários na área externa. Dois tipos de águas (claras, sem fitoplâncton ou verdes, ricas em fitoplâncton) e três diferentes manejos de qualidade de água (nenhum, acidificação com HCl ou calagem com Na2CO3) foram avaliados simultaneamente em delineamento fatorial 3 x 2. A concentração de amônia total, dureza cálcica, pH e alcalinidade total das águas verdes foram significativamente maiores que para as águas claras. A calagem das águas fracamente ácidas com Na2CO3 não produziu nenhum efeito significativo na dureza cálcica da água. Não se observaram diferenças significativas entre os grupos-controle e o grupo experimental para nenhuma das variáveis de desempenho produtivo observadas. Concluiu-se que fazer a calagem da água de cultivo de tilápias com Na2CO3 não trará nenhum benefício ao desempenho zootécnico dos peixes se a alcalinidade inicial da água exceder 20 mg L-1 de CaCO3.

Growth performance of Nile tilapia, Oreochromis niloticus, fingerlings reared in Na2CO3 limed waters / Desempenho produtivo de alevinos de tilápia nilótica, Oreochromis niloticus, em aquários submetidos à calagem com Na2CO3

Current experiment was undertaken during 6 weeks with Nile tilapia, Oreochomis niloticus, fingerlings (1.28  0.03 g) to assess the effects of moderate Na2CO3 liming on water quality and fish growth performance. Twenty-four 25 L-aquaria, with 15 fish per aquarium, were used, of which twelve aquaria were placed in the labs indoor room and twelve in the outdoor area. Two types of water (clear or green) and three different water-quality managements (none, HCl acidification and Na2CO3 liming) were simultaneously evaluated in a 3 x 2 factorial design. Total ammonia, calcium hardness, pH and total alkalinity in the green water aquaria were significantly higher than rates in the clear water aquaria. Slight liming acid water with Na2CO3 did not produce any significant effect on its water calcium hardness. No significant differences between controls and the experimental group were observed for any growth variables. Lime rearing water with Na2CO3 has no significant effect on tilapia growth performance if the initial total alkalinity of water is higher than 20 mg CaCO3 L-1.(AU)

O presente estudo foi realizado por seis semanas com alevinos de tilápia do Nilo, Oreochromis niloticus (1,28 +/- 0,03 g), para avaliar os efeitos da calagem moderada da água de cultivo com Na2CO3 na qualidade da água e no desempenho produtivo dos peixes cultivados. Vinte e quatro aquários de polietileno de 25 L foram utilizados para manter os peixes experimentais (15 peixes por aquário). Doze aquários foram instalados na sala interna do laboratório e 12 aquários na área externa. Dois tipos de águas (claras, sem fitoplâncton ou verdes, ricas em fitoplâncton) e três diferentes manejos de qualidade de água (nenhum, acidificação com HCl ou calagem com Na2CO3) foram avaliados simultaneamente em delineamento fatorial 3 x 2. A concentração de amônia total, dureza cálcica, pH e alcalinidade total das águas verdes foram significativamente maiores que para as águas claras. A calagem das águas fracamente ácidas com Na2CO3 não produziu nenhum efeito significativo na dureza cálcica da água. Não se observaram diferenças significativas entre os grupos-controle e o grupo experimental para nenhuma das variáveis de desempenho produtivo observadas. Concluiu-se que fazer a calagem da água de cultivo de tilápias com Na2CO3 não trará nenhum benefício ao desempenho zootécnico dos peixes se a alcalinidade inicial da água exceder 20 mg L-1 de CaCO3. (AU)