Post-feeding Molecular Responses of Cobia (Rachycentron canadum): RNA-Sequencing as a Tool to Evaluate Postprandial Effects in Hepatic Lipid Metabolism.

We used transcriptome sequencing to investigate the hepatic postprandial responses of Rachycentron canadum (cobia), an important commercial fish species. In total, 150 cobia juveniles (50 per tank, triplicate) were fed ad libitum with a commercial diet for 7 days, fasted for 24 h, and fed for 10 min. The liver was sampled 10 min prior to feeding and 30 min, 1, 2, 4, 8, 12, and 24 h after the feeding event. Each sample was evaluated in terms of liver fatty acid profile and gene expression. Differential gene expressions were evaluated, focusing on fatty acid synthesis and oxidation pathways. In general, the liver fatty acid profile reflected diet composition. Docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) levels increased at 8 to 12 h but decreased at 24 h after the feeding event. A high number of differentially expressed genes (DEGs) were observed comparing fish that fasted for 8 h with those fasted for 30 min and 24 h, while a reduced number of DEGs was observed comparing individuals who fasted for 30 min compared with those who fasted for 24 h. Similarly, the main differences in the expression of genes related to the fatty acid biosynthesis and oxidation pathways were noticed in individuals who fasted for 8 h compared with those who fasted for 30 min and 24 h. The results suggested that the adequate time to sample the individuals ranged between 8 and 12 h after the meal since, apparently, after 24 h, differential gene expression was not necessarily influenced by food intake.

Common moist diet replacement to promote sustainable Cobia Rachycentron canadum (Linnaeus) near - shore farming in Brazil

Cobia is one of the most promising warm water aquaculture species. In Brazil, cobia farming began in 2008 in the state of Rio de Janeiro from experimental scale facilities to regular near-shore farms based on fresh/frozen fish diets composed mostly of Sardinella sp. Despite the encouraging results achieved in the promotion of sustainable cobia farming, we advocate the replacement of fresh/frozen fish by a practical formulated feed. This experiment evaluated the zootechnical performance and environmental efficiency of moist and practical formulated feeds in early grow-out phases in the cycle of cobia nearshore cage culture. Four hundred and twenty juvenile cobia (151 ± 7 g) were fed with moist feed and practical formulated feed for 56 days. Biometrics were taken every two weeks and diets were analyzed for proximate composition, fatty acid composition and pellet quality. Although growth performance was equivalent between treatments, feed consumption and feed conversion ratios (FCR) were different (p < 0.05) and varied according to water temperature. Cobia fed moist feed exhibited an FCR two times higher than those fed formulated feed. Elevated settling speed and low floatability contributed to higher heterogeneity and lower efficiency of fish fed moist diet. Nitrogen excretion rate was reduced (64 %) and protein efficiency ratio elevated (27 %) within formulated diet groups in comparison to those fed moist diet (79 % and 15 %, respectively). The fatty acid profile of cobia muscle was similar across the groups. With no negative effects of diet substitution on production performance and improvement of environmental efficiency, this approach can be applied and advocated globally and contribute to the responsible intensification of sustainable marine fish culture.(AU)

Common moist diet replacement to promote sustainable Cobia Rachycentron canadum (Linnaeus) near - shore farming in Brazil

Cobia is one of the most promising warm water aquaculture species. In Brazil, cobia farming began in 2008 in the state of Rio de Janeiro from experimental scale facilities to regular near-shore farms based on fresh/frozen fish diets composed mostly of Sardinella sp. Despite the encouraging results achieved in the promotion of sustainable cobia farming, we advocate the replacement of fresh/frozen fish by a practical formulated feed. This experiment evaluated the zootechnical performance and environmental efficiency of moist and practical formulated feeds in early grow-out phases in the cycle of cobia nearshore cage culture. Four hundred and twenty juvenile cobia (151 ± 7 g) were fed with moist feed and practical formulated feed for 56 days. Biometrics were taken every two weeks and diets were analyzed for proximate composition, fatty acid composition and pellet quality. Although growth performance was equivalent between treatments, feed consumption and feed conversion ratios (FCR) were different (p < 0.05) and varied according to water temperature. Cobia fed moist feed exhibited an FCR two times higher than those fed formulated feed. Elevated settling speed and low floatability contributed to higher heterogeneity and lower efficiency of fish fed moist diet. Nitrogen excretion rate was reduced (64 %) and protein efficiency ratio elevated (27 %) within formulated diet groups in comparison to those fed moist diet (79 % and 15 %, respectively). The fatty acid profile of cobia muscle was similar across the groups. With no negative effects of diet substitution on production performance and improvement of environmental efficiency, this approach can be applied and advocated globally and contribute to the responsible intensification of sustainable marine fish culture.

Feeding frequency affects growth of juvenile cobia Rachycentron canadum cultured in near-shore cages / Efeito da frequência alimentar no crescimento de juvenis de bijupirá Rachycentron canadum criados em tanques tipo near-shore

Growth performance of juvenile cobia Rachycentron canadum (15.7 ± 0.4 g; mean ± SD) reared in 1 m3 near-shore cages, 24.0 ± 2.1 ºC, fed a Brazillian commercial feed (45% crude protein and 16% lipid) until apparent satiation, in a single feeding (F1), two (F2) or three (F3) feedings per day, for 30 days was assessed. The initial stocking density was 0.6 kg m-3. Production performance of juvenile cobia was significantly affected by feeding frequency. Groups fed two and three equal feedings per day presented greater and more efficient growth than F1 groups. There was no difference between F2 and F3 treatments for weight gain (15.6 ± 1.5 g and 16.3 ± 2.0 g, respectively), specific growth rate (SGR: 2.3 ± 0.3% and 2.5 ± 0.4% of body weight per day, respectively) and feed conversion ratio (FCR: 2.3 ± 0.2 and 2.5 ± 0.3, respectively). However, these parameters were reduced in F1 treatment (weight gain of 8.4 ± 1.1 g; SGR = 1.4 ± 0.2% and FCR = 3.2 ± 0.6) (P 0.05). The coefficient of variation was inversely proportional to the increase in feeding frequency. There was no significant difference in terms of survival rates, being superior to 90% in all treatments. We suggestthat growth performance of juvenile cobia cultured in near-shore cages can be optimized at a feeding frequency of two times a day, facilitating husbandry procedures and minimizing costs related to labor and vessel utilization.(AU)

O desempenho de juvenis de bijupirá Rachycentron canadum (15,7 ± 0,4 g; média ± DP) criados em tanques-rede de 1 m³, em uma baía protegida, 24,0 ± 2,1 C, alimentados com uma ração comercial brasileira (45% de proteína bruta e 16% de gordura) até saciedade aparente, alimentados em uma (F1), duas (F2) e três (F3) refeições por dia, durante 30 dias, foi avaliado. A densidade de estocagem inicial foi de 0,6 kg m-3. O desempenho de produção de juvenis de bijupirá foi afetado significativamente pela frequência alimentar. Grupos alimentados duas e três vezes ao dia apresentaram um crescimento maior e mais eficiente do que os grupos F1. Não houve diferença entre os tratamentos F2 e F3 para o ganho em peso (15,6 ± 1,5 g e 16,3 ± 2,0 g, respectivamente), taxa de crescimento específica (TCE: 2,3 ± 0,3% e 2,5 ± 0,4% do peso corporal diário, respectivamente) e conversão alimentar aparente (CAA: 2,3 ± 0,2 e 2,5 ± 0,3, respectivamente). No entanto, os tratamentos F2 e F3 promoveram melhores resultados comparados ao tratamento F1 (ganho em peso: 8,4 ± 1,1 g; TCE = 1,4 ± 0,2%; CAA = 3,2 ± 0,6) (p 0,05). O coeficiente de variação foi inversamente proporcional ao aumento da frequência alimentar. Não houve diferença significativa para taxa de sobrevivência, sendo superior a 90% em todos os tratamentos. Este trabalho sugereque o desempenho do crescimento de juvenis de bijupirá criados em condições do presente estudo pode ser otimizado quando alimentados duas vezes ao dia, facilitando os procedimentos de criaçãoe minimizando os custos relacionados com mão-de-obra e embarcação.(AU)

Feeding frequency affects growth of juvenile cobia Rachycentron canadum cultured in near-shore cages / Efeito da frequência alimentar no crescimento de juvenis de bijupirá Rachycentron canadum criados em tanques tipo near-shore

Growth performance of juvenile cobia Rachycentron canadum (15.7 ± 0.4 g; mean ± SD) reared in 1 m3 near-shore cages, 24.0 ± 2.1 ºC, fed a Brazillian commercial feed (45% crude protein and 16% lipid) until apparent satiation, in a single feeding (F1), two (F2) or three (F3) feedings per day, for 30 days was assessed. The initial stocking density was 0.6 kg m-3. Production performance of juvenile cobia was significantly affected by feeding frequency. Groups fed two and three equal feedings per day presented greater and more efficient growth than F1 groups. There was no difference between F2 and F3 treatments for weight gain (15.6 ± 1.5 g and 16.3 ± 2.0 g, respectively), specific growth rate (SGR: 2.3 ± 0.3% and 2.5 ± 0.4% of body weight per day, respectively) and feed conversion ratio (FCR: 2.3 ± 0.2 and 2.5 ± 0.3, respectively). However, these parameters were reduced in F1 treatment (weight gain of 8.4 ± 1.1 g; SGR = 1.4 ± 0.2% and FCR = 3.2 ± 0.6) (P 0.05). The coefficient of variation was inversely proportional to the increase in feeding frequency. There was no significant difference in terms of survival rates, being superior to 90% in all treatments. We suggestthat growth performance of juvenile cobia cultured in near-shore cages can be optimized at a feeding frequency of two times a day, facilitating husbandry procedures and minimizing costs related to labor and vessel utilization.

O desempenho de juvenis de bijupirá Rachycentron canadum (15,7 ± 0,4 g; média ± DP) criados em tanques-rede de 1 m³, em uma baía protegida, 24,0 ± 2,1 C, alimentados com uma ração comercial brasileira (45% de proteína bruta e 16% de gordura) até saciedade aparente, alimentados em uma (F1), duas (F2) e três (F3) refeições por dia, durante 30 dias, foi avaliado. A densidade de estocagem inicial foi de 0,6 kg m-3. O desempenho de produção de juvenis de bijupirá foi afetado significativamente pela frequência alimentar. Grupos alimentados duas e três vezes ao dia apresentaram um crescimento maior e mais eficiente do que os grupos F1. Não houve diferença entre os tratamentos F2 e F3 para o ganho em peso (15,6 ± 1,5 g e 16,3 ± 2,0 g, respectivamente), taxa de crescimento específica (TCE: 2,3 ± 0,3% e 2,5 ± 0,4% do peso corporal diário, respectivamente) e conversão alimentar aparente (CAA: 2,3 ± 0,2 e 2,5 ± 0,3, respectivamente). No entanto, os tratamentos F2 e F3 promoveram melhores resultados comparados ao tratamento F1 (ganho em peso: 8,4 ± 1,1 g; TCE = 1,4 ± 0,2%; CAA = 3,2 ± 0,6) (p 0,05). O coeficiente de variação foi inversamente proporcional ao aumento da frequência alimentar. Não houve diferença significativa para taxa de sobrevivência, sendo superior a 90% em todos os tratamentos. Este trabalho sugereque o desempenho do crescimento de juvenis de bijupirá criados em condições do presente estudo pode ser otimizado quando alimentados duas vezes ao dia, facilitando os procedimentos de criaçãoe minimizando os custos relacionados com mão-de-obra e embarcação.

Outbreak of mortality among cage-reared cobia (Rachycentron canadum) associated with parasitism / Surto de mortalidade em bijupirá (Rachycentron canadum) criado em tanque-rede associado ao parasitismo

This study reports a disease outbreak among juvenile cobia (Rachycentron canadum) farmed in cages in the state of Rio de Janeiro, Brazil, caused by the dinoflagellate Amyloodinium ocellatum and the monogenean Neobenedenia melleni. Two thousand five hundred fish were stocked at 0.4 kg/m3 in a set of 12 m3 tanks, in autumn (mean weight 15.0 ± 7.3 g) and in winter (mean weight 43.0 ± 5.6 g). Freshwater baths were administered as a routine treatment, as the symptoms were detected followed by two collection samples. Firstly in May 2011 (n = 5) and secondly in September 2011 (n = 10). In the first sample, the prevalence of N. melleni on the body surface was 100% and the mean intensity was 42.0 ± 1.7, while in the second sample the prevalence was 60% with a mean intensity 3.0 ± 0.2 and mean abundance 1.8 ± 0.4. Amyloodinium ocellatum was only found in the second sample, at a prevalence 100% and mean intensity 46.8 ± 3.4. The cause of fish mortality was possibly associated with a decrease in fish resistance after the first contact with monogenean parasites, allied with respiratory difficulty caused by the presence of A. ocellatum in the gills.

Este estudo relata a mortalidade em massa de juvenis de bijupirá (Rachycentron canadum) criados em tanques-rede no estado do Rio de Janeiro, Brasil, causada pelo dinoflagelado Amyloodinium ocellatum e o monogenea Neobenedenia melleni. Dois mil e quinhentos peixes estavam estocados à densidade de 0,4 kg/m3 em tanques-rede de 12 m3, no período do outono (15,0 ± 7,3 g; peso médio ± DP) e inverno (peso médio de 43,0 ± 5,6 g). Banhos de água doce foram realizados rotineiramente à medida que os sintomas eram detectados, quando então, foram efetuadas duas colheitas, sendo a primeira em maio de 2011 (n = 5) e a segunda em setembro de 2011 (n = 10). Na primeira colheita, a prevalência de N. melleni foi de 100% e a intensidade média de 42,0 ± 1,7, e na segunda, a prevalência foi de 60% e intensidade média de 3,0 ± 0,2 e abundância média de 1,8 + 0,4. Na segunda colheita, observou-se a presença de A. ocellatum (prevalência de 100%, intensidade média de 46,8 ± 3,4). Possivelmente, a causa da mortalidade estava relacionada à redução na resistência dos peixes após o primeiro contato com o parasito monogenea, juntamente com a dificuldade respiratória causada pelo dinoflagelado nas brânquias.

Outbreak of mortality among cage-reared cobia (Rachycentron canadum) associated with parasitism.

This study reports a disease outbreak among juvenile cobia (Rachycentron canadum) farmed in cages in the state of Rio de Janeiro, Brazil, caused by the dinoflagellate Amyloodinium ocellatum and the monogenean Neobenedenia melleni. Two thousand five hundred fish were stocked at 0.4 kg/m3 in a set of 12 m3 tanks, in autumn (mean weight 15.0 ± 7.3 g) and in winter (mean weight 43.0 ± 5.6 g). Freshwater baths were administered as a routine treatment, as the symptoms were detected followed by two collection samples. Firstly in May 2011 (n = 5) and secondly in September 2011 (n = 10). In the first sample, the prevalence of N. melleni on the body surface was 100% and the mean intensity was 42.0 ± 1.7, while in the second sample the prevalence was 60% with a mean intensity 3.0 ± 0.2 and mean abundance 1.8 ± 0.4. Amyloodinium ocellatum was only found in the second sample, at a prevalence 100% and mean intensity 46.8 ± 3.4. The cause of fish mortality was possibly associated with a decrease in fish resistance after the first contact with monogenean parasites, allied with respiratory difficulty caused by the presence of A. ocellatum in the gills.

Outbreak of mortality among cage-reared cobia (Rachycentron canadum) associated with parasitism

This study reports a disease outbreak among juvenile cobia (Rachycentron canadum) farmed in cages in the state of Rio de Janeiro, Brazil, caused by the dinoflagellate Amyloodinium ocellatum and the monogenean Neobenedenia melleni. Two thousand five hundred fish were stocked at 0.4 kg/m3 in a set of 12 m3 tanks, in autumn (mean weight 15.0 ± 7.3 g) and in winter (mean weight 43.0 ± 5.6 g). Freshwater baths were administered as a routine treatment, as the symptoms were detected followed by two collection samples. Firstly in May 2011 (n = 5) and secondly in September 2011 (n = 10). In the first sample, the prevalence of N. melleni on the body surface was 100% and the mean intensity was 42.0 ± 1.7, while in the second sample the prevalence was 60% with a mean intensity 3.0 ± 0.2 and mean abundance 1.8 ± 0.4. Amyloodinium ocellatum was only found in the second sample, at a prevalence 100% and mean intensity 46.8 ± 3.4. The cause of fish mortality was possibly associated with a decrease in fish resistance after the first contact with monogenean parasites, allied with respiratory difficulty caused by the presence of A. ocellatum in the gills.

Este estudo relata a mortalidade em massa de juvenis de bijupirá (Rachycentron canadum) criados em tanques-rede no estado do Rio de Janeiro, Brasil, causada pelo dinoflagelado Amyloodinium ocellatum e o monogenea Neobenedenia melleni. Dois mil e quinhentos peixes estavam estocados à densidade de 0,4 kg/m3 em tanques-rede de 12 m3, no período do outono (15,0 ± 7,3 g; peso médio ± DP) e inverno (peso médio de 43,0 ± 5,6 g). Banhos de água doce foram realizados rotineiramente à medida que os sintomas eram detectados, quando então, foram efetuadas duas colheitas, sendo a primeira em maio de 2011 (n = 5) e a segunda em setembro de 2011 (n = 10). Na primeira colheita, a prevalência de N. melleni foi de 100% e a intensidade média de 42,0 ± 1,7, e na segunda, a prevalência foi de 60% e intensidade média de 3,0 ± 0,2 e abundância média de 1,8 + 0,4. Na segunda colheita, observou-se a presença de A. ocellatum (prevalência de 100%, intensidade média de 46,8 ± 3,4). Possivelmente, a causa da mortalidade estava relacionada à redução na resistência dos peixes após o primeiro contato com o parasito monogenea, juntamente com a dificuldade respiratória causada pelo dinoflagelado nas brânquias.