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Deleterious changes in metabolism, growth performance and body composition may be observed if fish are constrained to swimming continuously or intermittently at over-speeds. This study evaluates effects of four water speeds on growth, body composition and hematologic profile of juvenile matrinxã, Brycon amazonicus. Fish (33.3 ± 0.9 g and 13.44 ± 0.1 cm) were held for 90 days in five water speeds (0.0 - control, 1.0, 1.5, 2.0 and 2.5 body lengths per second - BLAt swimming speeds ranging on 1.0 and 1.5 BL s–1, in fish growth was 20% higher. Hemoglobin and red blood cells at 1.5 BL s–1 increased 24% and 18% respectively; hematocrit was 17% higher in all exercised fish; protein content of white muscle at 1.0 BL s–1 was 2% higher; lipid deposition in red muscle at 1.0 BL s–1 was 22% higher and water retention 3% lower. Crude energy levels enhanced 10% in all exercised fish; liver water retention was 6% lower at 1.0 BL s–1; liver lipid composition was 29% higher than control and 34% higher than 1.5 BL s–1; liver crude energy increased at 1.0 BL s–1 as compared with control and 2.5 BL s–1. Lipid deposition in ventral muscle was 9% higher at 2.0 BL s–1. Although high lipid deposition of matrinxã has been achieved in moderate swimming speeds, lipids may be the main fuel source to maintain the metabolic demands of exercised matrinxã. The best water flow speed for optimized growth of matrinxã ranged on 1.0 and 1.5 BL s–1.Modificações deletérias no metabolismo, rendimento de crescimento e composição corporal podem ser observadas em peixes forçados à natação contínua ou intermitente sob velocidades excessivas. Neste trabalho, os efeitos de quatro velocidades de água no crescimento, composição corporal e perfil hematológico foram avaliados em matrinxãs juvenis, Brycon amazonicus. Os peixes (33,3 ± 0,9 g e 13,44 ± 0,1 cm) foram mantidos durante 90 dias em cinco velocidades de água (0,0 – controle; 1,0; 1,5; 2,0 e 2,5 comprimentos corporais - BL por segundo). As melhores velocidades de nadado estiveram entre 1,0 e 1,5 BL s–1, nas quais o crescimento dos peixes foi 20% maior que nas outras. A hemoglobina e as células vermelhas do sangue em 1,5 BL s–1 aumentaram 24% e 18% respectivamente; o hematócrito foi 17 % maior em todos os peixes exercitados; o conteúdo de proteína do músculo branco em 1,0 BL s–1 foi 2% maior; a deposição de lipídio no músculo vermelho em 1,0 BL s–1 foi 22% maior e a retenção de água foi 3% menor. Os níveis de energia bruta aumentaram 10% em todos os peixes exercitados; a retenção de água no fígado foi 6 % menor em 1,0 BL s–1; a composição de lipídio no fígado foi 29% maior do que o controle e 34% maior do que a 1,5 BL s–1; a energia bruta no fígado aumentou em 1.0 BL s–1 comparada com o controle e 2,5 BL s–1. A deposição de lipídio no músculo ventral foi 9% maior em 2,0 BL s–1. Embora alta deposição de lipídio em matrinxã tenha sido obtida em velocidades moderadas de nado, os lipídios podem ser a fonte de combustível principal para manter as exigências metabólicas de matrinxã em exercício. A melhor velocidade de nado para obter o melhor crescimento em matrinxã está entre 1,0 e 1,5 BL s–1.

La historia del crecimiento individual de los peces se encuentra registrada en las marcas presentes en las estructuras duras como otolitos, escamas, vértebras, huesos y radios. El análisis retrospectivo o retrocálculo es una técnica que permite utilizar esa información para estimar dimensiones corporales en edades o etapas previas de la historia de vida, a través de relaciones entre mediciones realizadas en la estructura dura y las dimensiones del pez. En este trabajo se revisan los métodos de retrocálculo más ampliamente utilizados en peces y sus supuestos, con énfasis en la relación tamaño de la estructura dura - longitud del pez. La estructura dura más utilizada corresponde a los otolitos sagittae de los peces teleósteos, y aunque se hace referencia a ellos la técnica es aplicable a otras estructuras duras. Se distinguen dos aproximaciones: a) los métodos proporcionales; y, b) el método de regresión, ambas aproximaciones utilizan los parámetros de la ecuación que relaciona la longitud del pez y el tamaño del otolito al momento de la captura. El método de regresión no toma en cuenta la variación en el tamaño del otolito entre los peces; mientras que los métodos proporcionales incorporan la información de cada pez lo que da cuenta de la variación individual. Ambas aproximaciones asumen que existe una proporcionalidad entre el crecimiento somático y el crecimiento del otolito. A pesar del amplio uso que se hace del retrocálculo en estudios de crecimiento, a la técnica se le ha dado una importancia menor al momento de aplicarlo, lo que indica que es pobremente entendido. Aún cuando todos los métodos de retrocálculo se basan en la hipótesis de existencia de una proporcionalidad entre el crecimiento del otolito y el crecimiento del pez, sin embargo hay un número de especies en los cuales la relación longitud pez-otolito no es lineal. Un buen entendimiento de la relación entre el tamaño del otolito y tamaño del cuerpo puede llevar a mejorar la exactitud de los métodos de retrocálculo aplicado a cada especie. El desarrollo de los métodos de retrocálculo debería estar orientada hacia el diseño de algoritmos que consideren la tasa de crecimiento tiempo-variante. Por último, debido a la naturaleza de las mediciones (medidas repetidas y autocorrelación) los esfuerzos debieran dirigirse hacia la aplicación de métodos estadísticos apropiados y al uso de series de tiempoThe individual fish growth history is recorded in the marks of hard structures, such as otoliths, scales, vertebrates, bones and rays. The retrospective analysis or back-calculation is a technique that allows to use this information to estimate body dimensions at previous ages or stages in the fish life history. This is achieved by using relationships between measurements taken from the hard structure and the body fish. In this paper, the more widely back-calculation methods used in fish are reviewed, as well as the main assumptions in the relationships between the hard structure size and the fish length. In teleosts, the more used hard structure have been the sagittae otoliths and although the technique can be applied to other hard structures, the otoliths are used as a reference. Two approaches are distinguished: a) the proportional methods, and b) the regression method, both approaches begin with estimates of the parameters for the equation that relates the fish length and the otolith size at the moment of the capture. The regression method does not take into account the individual variation in size of fish otoliths. On the contrary, the proportional methods use the information of each fish, i.e. the individual variation. However, both approaches assume that there are a direct proportion between the somatic growth and the otolith growth. In spite of the wide use of back-calculation methods in age and growth studies, the importance of the back-calculation technique have been overlooked when this is applied. This means that the technique is poorly understood. . All the back-calculation methods are based on the proportion between the otolith growth and body growth. However, there is a number of species in which the relationships between body fish and otolito size is non-linear. Better understanding of the relationships between otolith size and body size should improve the accuracy of back-calculation methods, mainly in those where readiness of data exists. The development of back-calculation methods should be addressed to the design of algorithms that consider the time-varying growth rate. Finally, because there are repeated measures and autocorrelation in back-calculation methods the research efforts should be oriented to improve the application of appropriate statistical methods and the uses of time series

Diapterus rhombeus es una especie dominante dentro de la comunidad nectónica de la Laguna de Términos y se encuentra asociada a zonas con vegetación sumergida, con temperaturas entre 27 y 33°C y salinidad entre 25 y 36.5 UPS. Un total de 3024 individuos fueron recolectados con una red de arrastre en 23 sitios entre septiembre de 1997 y septiembre de 1998. Los parámetros del modelo Talla-Peso son a=0.0098; b=3.155 con una correlación del 96%. Los parámetros de crecimiento son L = 20.4cm, k= 0.74 y t o= -4.207 con un coeficiente de mortalidad total de 3.526. La población está representada por organismos con tallas entre 2.5 y 18.0 cm con una moda de 7.5 cm. El reclutamiento es continuo con un marcado pulso entre mayo y agosto. La especie utiliza distintos hábitat dentro de la Laguna de Términos principalmente para fines de alimentación y crecimiento y es probable que la maduración y reproducción se desarrollen en la plataforma continental adyacente. Estos movimientos de la especie se traducen en un continuo flujo de energía entre ambos sistemas.Diapterus rhombeus dominates the nektonic community of Terminos Lagoon and is associated to zones with submerged vegetation, temperatures between 27 and 33°C and salinity between 25 and 36.5 UPS. A total of 3 024 individuals were collected with a trawl net in 23 sites between September 1997 and September 1998. The length-weight model parameters are a=0.0098; b = 3.155 with a 96% correlation. The growth parameters are L = 20.4 cm, k = 0.74 and t o= - 4.207 and the total mortality coefficient is 3.526. Fish length is 2.5 - 18.0 cm with a mode of 7.5 cm. Recruitment is continuous with a peak from May to August. The species uses several habitats of the lagoon mainly for feeding and growth, reproduction probably occurs in the adjacent continental shelf. Movements between continental shelf and the estuarine system represent a continuous energy flow.