Feeding behaviour, locomotion rhythms and blood biochemistry of the neotropical red-tail catfish (Phractocephalus hemioliopterus).

The study evaluated the feeding behaviour of Phractocephalus hemioliopterus through the animals' ability to adapt to the self-feeding system, their preferred feeding times and locomotor activity, as well as the blood biochemistry of juveniles fed in a light/dark cycle. The study was carried out through two experiments, the first of which contained two phases. In experiment 1 - phase I, 24 juveniles (35.28 ± 0.62 g) were distributed in eight 48 l tanks. The tanks were equipped with a self-feeding system and the experiment consisted of evaluating whether the animals were able to adapt to the self-feeding system, as well as evaluating the preferred feeding times and locomotor activity of these animals. A feeding challenge to the animals was introduced in phase II, based on the results of phase I. The results of the first phase evidenced a nocturnal feeding preference. Thus, the feeding challenge consisted of measuring whether the animal would feed during the day and how long it would take to adapt. When the animals consumed 100% of the amount of feed provided daily, phase II was ended. In experiment 2, 24 juveniles of P. hemioliopterus (182.00 ± 14.03 g) were distributed in eight 96 l tanks. This experiment consisted of two treatments with four repetitions, one with exclusive feeding during the middle of the light cycle and another with exclusive feeding in the middle of the dark cycle. At the end, blood samples were collected from the animals for blood biochemistry evaluations. In experiment 1 - phase I, the results showed that the fish adapted very well to the self-feeding system and had a strictly nocturnal feeding behaviour and locomotor rhythm. When they were submitted to the feeding challenge in phase II, the feed intake was stabilized from the 17th day onwards, proportionally to the nocturnal consumption observed in the first phase, thus demonstrating feeding plasticity. In experiment 2, the feeding times influenced the animals' biochemical parameters. Animals fed during the night had higher values of cholesterol and triglycerides than animals fed during the day. It is concluded that P. hemioliopterus has fast adaptability to a self-feeding system, with strictly nocturnal feeding and locomotor behaviours. However, it has feeding plasticity, adapting its behaviour according to food availability. Blood biochemical parameters are influenced by the light/dark feeding cycle.

Feeding and locomotor rhythm of the ornamental cichlid fish Amatitlania sp. in different social groups.

The aim of this study was to evaluate the feeding activity and the rhythm of daily locomotor activity of the convict cichlid (Amatitlania sp.) kept in different social groups under a self-feeding system. A total of 120 animals was distributed among six repetitions of four social groups, as follows: group 1 with one male and one female per tank; group 2 with three males and three females per tank; group 3 with six males per tank; and group 4 with six females per tank. Feeding activity (FA) and locomotor activity (LA) were evaluated using photoelectric presence-sensors connected to automatic feeders. The fish were fed a commercial extruded diet (46% crude protein and 3600 kcal kg-1 of digestible energy). Animal growth was evaluated for all groups. After 30 days of experimentation, the fish stabilized their demands by adjusting their consumption. Amatitlania sp. showed predominantly diurnal FA and LA. All groups showed a peak of activity when the light was turned on and when it was turned off. In summary, FA and LA of Amatitlania sp. are predominantly diurnal and independent of social group. Pairs and groups of males and females together consume less food in relation to groups of one sex or the other due to reproductive behaviour. On the other hand, groups of only males or females consume more food because they lack reproductive stimuli and thus prioritize growth. These results may support good feeding management practices for this ornamental cichlid. Studies relating feeding behaviour with different social groups are of great importance for determining effective feeding strategies for this species in captivity. Thus, such a study assists in a more efficient production of Amatitlania sp.

Aceite de clavo como anestésico para el pez Pacu (piaractus mesopotamicus) / Clove oil as an anesthetic for pacu fish (piaractus mesopotamicus)

Con el propósito de minimizar el daño causado a los peces por el uso de sustancias anestésicas, se ha evaluado, en este trabajo, la concentración más adecuada de aceite de clavo como anestésico para el pez pacu (Piaractus mesopotamicus). Fueron utilizados 40 peces, con peso promedio de 716,18 g. Los tratamientos fueron compuestos de soluciones con diferentes concentraciones de aceite de clavo, 30, 60, 90, 120 y 150 mg/L. Fueron utilizados dos acuarios de vidrio: uno con 20 litros de agua con la solución anestésica para cada tratamiento y otro con 20 litros de agua limpia, para el regreso de los animales de la condición de sedación. Se observaron de forma individual: el tiempo hasta llegar a la anestesia profunda y el tiempo de recuperación de la anestesia profunda. El diseño experimental fue completamente aleatorizado con cinco tratamientos (concentraciones de aceite de clavo) y ocho repeticiones (peces). Los tiempos hasta anestesia profunda e hasta la recuperación total de los peces fueron evaluados por regresión, con 5% de significancia. Se observó un comportamiento linear de los tiempos hasta la anestesia profunda y hasta la recuperación total de los peces a concentraciones crecientes de aceite de clavo. La concentración de 30 mg/L es suficiente para la inducción anestésica de los animales, por otra parte, las concentraciones más elevadas, hasta 150 mg/L, causaron inducciones aún más rápidas, sin pérdida en las condiciones para la recuperación de los peces(AU)

In order to minimize damage to fish caused by the use of anesthetic substances, this study was to evaluate the concentration of clove oil as an anesthetic most appropriate for pacu (Piaractus mesopotamicus). A total of 40 fishes, with average weight of 716.18 g. The treatments were: anesthetic procedures with solutions of different concentrations of clove oil, 30, 60, 90, 120 and 150 mg.L-1. We used two glass aquariums: one with 20 liters of water containing the anesthetic solution for each treatment and the other with 20 liters of clean water, the animals return to the condition of sedation. Were observed individually: the time to reach deep anesthesia and recovery time of deep anesthesia. The experimental design was completely randomized design with five treatments (concentrations of clove oil) and eight replicates (individuals). The data were submitted to regression, with 5% significance level. There was a linear time of anesthesia and return of fish to increasing concentrations of clove oil, and 30 mg.L-1 is sufficient for the induction of the animals, but higher concentrations of up to 150 mg.L-1, still show inductions faster, without loss in time and conditions for the recovery of fish(AU)

Parámetros morfométricos en el rendimiento de los componentes corporales de Tilapia del Nilo (Oreochromis niloticus) / Morphometric Measurements in the Yield of Body Component in Nile of Tilapia (Oreochromis niloticus)

Con el propósito de estudiar los efectos de los parámetros morfométricos en el rendimiento corporal de la tilapia del Nilo (Oreochromis niloticus), se realizó este trabajo en la Universidad Federal de Lavras-MG, Brasil. Fueron mantenidos 1000 juveniles de linajes Supreme y Chitralada, con peso inicial entre 0,5 y 1,0 g, en separado, en dos tanques de cemento (40 m3). Fueron retiradas muestras y las medidas del alto, ancho y perímetros de las regiones del primer radio de las aletas dorsal, anal y de la circunferencia anterior del pedúnculo caudal, así como el largo de la cabeza y longitud total, fueron obtenidas de 78 peces de linaje Supreme y 93 de Chitralada. Los peces fueron pesados y disecados para obtención de los rendimientos de escamas y aletas, vísceras, cabeza, canal, piel, filete y residuo. Fueron hechos los análisis de correlación, el agrupamiento de variables en el dendograma y la regresión múltiple de los datos por el método backward para el estudio de la variación en los rendimientos corporales. Los rendimientos de los componentes corporales, en general, están poco relacionados con las medidas morfométricas. Los rendimientos de la canal y filete fueron calculados por las ecuaciones de regresión: RCAR = 43,2426 + 79,6399 LC2/CP (R2=0,096) y RFSP = 36,028 – 1,7415 AC1/LC2 (R2 = 0,014). Los análisis de regresión indicaron que el ancho a nivel del primer radio de la aleta anal, con relación a largura padrón (LC2/CP) y la altura a nivel del primer radio de la aleta dorsal, con relación al ancho del primer rayo de la nadadera anal (AC1/LC2) contribuyeron para la variación, respectivamente, en los rendimientos de canal y filete (AU)

The aim of this experiment was to study the influence of the morphometric measurements on characteristics of weight and on body yields of Nile tilapia (Oreochromis niloticus), an experiment was conducted in the pisciculture sector of the Federal University of Lavras, MG. Fingerlings of the Supreme and the Chitralada strains, with an initial weight of 0.5 a 1.0 g, were stocked and reared separately in two ponds (40 m3). During fish growth, samples were taken in 78 individuals of the Supreme strain and 93 of the Chitralada. Measurements of height, width and perimeters on the regions of the first ray of the dorsal and anal fins and on the anterior circumference of the caudal peduncle as well as the head and standard lengths were obtained. In addition, fish were weighted and dissected for obtaining the weights and yields of scales, fins, viscera, head, carcass, skin, fillet and residue. The correlation and grouping analysis of the data obtained revealed a low association degree between the morphometric measurements with the yelds of body components. There was a similarity between head and standard lengths and between height and perimeter of each region. The regression analysis was accomplished for body yelds as related with the morphometric relationship by backward method. The relation between the first-ray anal fin width and CP (LC2/CP) and between the first-ray dorsal f n and LC2 (AC1/LC2) were related to carcass (RCAR) and fillet (RFSP) yields, respectively. These yields were estimated as, RCAR = 43.2426 + 79.6399 LC2/CP (R2=0.096) and RFSP = 36.028 – 1.7415 AC1/LC2 (R2 = 0,014). The morphometric relationship was that better explained the yeld of body components had have the measurements LC2/CP and AC1/LC2, respectively, of the carcass and fillet yelds (AU)