Resumo A seleção pode impactar a forma de crescimento, mudando o desempenho e os valores assintóticos. No entanto, existem poucas informações sobre o crescimento das famílias em programas de criação de peixes. O objetivo deste estudo foi examinar o desempenho e as curvas de crescimento de famílias de tilápia-do-Nilo AquaAmérica. Foram avaliadas 20 famílias AquaAmérica cultivadas em tanques-rede (13,5 m3) por 181 dias. O modelo de regressão não linear de Gompertz foi ajustado aos dados pelo método dos mínimos quadrados ponderados, tomando o inverso da variância do peso nas diferentes famílias e nas diferentes idades como variável de ponderação. O modelo foi ajustado para descrever o crescimento em peso e características morfométricas. Duas famílias apresentaram pesos maiores (P <0,05) em 133 dias (família AA10: 743,2 g; família AA16: 741,2 g) e 181 dias (família AA10: 1422,1 g; família AA16: 1393,4 g) de experimento em relação a outras famílias. Em ambos os períodos experimentais, os machos apresentaram maior peso, com maior contraste entre os sexos ocorrendo aos 181 dias. A análise das três famílias mais contrastantes (AA1, AA9 e AA14) mostrou que o valor assintótico para o peso foi maior (P <0,05) na família AA9 (3926,3 g) do que na família AA14 (3251,6 g), mas a taxa de crescimento específica e a idade no ponto de inflexão não diferiu significativamente entre as famílias. Em conclusão, duas das 20 famílias eram muito superiores; machos exibiram um maior crescimento, principalmente no período de 181 dias; e a curva de crescimento diferiu entre as famílias, principalmente quanto ao peso assintótico.

Abstract Selection can affect growth, changing performance and asymptotic values. However, there is little information about the growth of families in fish breeding programs. The aim of this study was to evaluate the performance and growth of families of Nile tilapia AquaAmérica. Twenty AquaAmérica families cultivated in a net cage (13.5 m3) for 181 days were evaluated. The nonlinear Gompertz regression model was fitted to the data by the weighted least squares method, taking the inverse of the variance of weight in different families and at different ages as the weighting variable. The model was adjusted to describe the growth in weight and morphometric characteristics. Two families showed highest (P<0.05) weights at both 133 days (family AA10: 743.2 g; family AA16: 741.2 g) and 181 days (family AA10: 1,422.1 g; family AA16: 1,393.4 g) of the experiment. In both experimental periods, the males showed a heavier weight, with the greatest contrast between the sexes occurring at 181 days. The analysis of the three most contrasting families (AA1, AA9 and AA14) showed that the asymptotic value for weight was higher (P<0.05) in family AA9 (3,926.3 g) than in family AA14 (3,251.6 g), but specific growth rate and age at the inflection point did not differ significantly between families. In conclusion, two of the 20 families were superior; males exhibited a greater growth, mainly in the period of 181 days; and the growth curve differed between the families, especially for asymptotic weight.

Resumo O objetivo do presente trabalho foi avaliar características qualitativas e quantitativas do sêmen de surubim do Iguaçu (Steindachneridion melanodermatum). Para as análises, utilizaram-se onze machos com peso médio de 1,76±0,48 kg e idade média de dois anos, submetidos ao tratamento de hipofisação. O volume médio de sêmen coletado foi de 1,34 ± 0,73 mL. O tempo médio de motilidade dos espermatozoides após a coleta foi de 154,4 ± 72,6 e 149,0 ± 77,5 segundos para ativação com água do tanque e água destilada, respectivamente. Para a concentração espermática, a média foi de 5,423 ± 2,155 x1010 espermatozoides/mL. Os resultados indicam que o sêmen de S. melanodermatum é facilmente obtido no período reprodutivo analisado, e que as características seminais avaliadas são adequadas para reprodução induzida.

Abstract The objective of the present work was to assess the qualitative and quantitative characteristics of semen from the surubim do Iguaçu (Steindachneridion melanodermatum). Induced spermiation was achieved in eleven males with mean weight of 1.76 ± 0.48 kg and average age of two years and semen was collected by stripping. The average volume was 1.34 ± 0.73 mL. The duration of sperm motility was 154.4 ± 72.6 and 149.0 ± 77.5 seconds after activation with hatchery water and distilled water, respectively. The sperm concentration estimated by hemocytometer was 5.423 ± 2.155 x 1010 spermatozoa/mL. The results indicate that S. melanodermatum semen is easily obtained during the spawning season and the seminal characteristics are adequate insemination and subsequent in vitro fertilization.

ABSTRACT In this paper, the existence of a genotype x environment interaction for the average daily weight in GIFT Nile tilapia (Oreochromis niloticus) in different regions in the state of Paraná (Brazil) was analyzed. The heritability results were high in the uni-characteristic analysis: 0.71, 0.72 and 0.67 for the cities of Palotina (PL), Floriano (FL) and Diamond North (DN), respectively. Genetic correlations estimated in bivariate analyzes were weak with values between 0.12 for PL-FL, 0.06 for PL and 0.23 for DN-FL-DN. The Spearman correlation values were low, which indicated a change in ranking in the selection of animals in different environments in the study. There was heterogeneity in the phenotypic variance among the three regions and heterogeneity in the residual variance between PL and DN. The direct genetic gain was greater for the region with a DN value gain of 198.24 g/generation, followed by FL (98.73 g/generation) and finally PL (98.73 g/generation). The indirect genetic gains were lower than 0.37 and greater than 0.02 g/generation. The evidence of the genotype x environment interaction was verified, which indicated the phenotypic heterogeneity of the variances among the three regions, weak genetic correlation and modified rankings in the different environments.

The conservation of genetic variability is a priority for fish lots used in restocking programs in rivers, especially for threatened or endangered fish species as is the case oí Brycon orbignyanus. The objective of this study was to estimate the genetic diversity and reproductive contribution of an offspring of B. orbignyanus used in stock programs in a semi-natural reproductive system using microsatellite markers. Samples of caudal fin from 24 breeders (12<img border=0 width=15 height=21 src="../../../../../img/revistas/agro/v44n2/a5s1.jpg"> and 12<img border=0 width=16 height=23 src="../../../../../img/revistas/agro/v44n2/a5s2.jpg">), and 95 larvae of their offspring. Breeders and offspring showed two alíeles, absence of low frequency alíeles and an average heterozygosity of 0.470 and 0.510. The coefficient Fis showed that there was no inbreeding in breeders and offspring (-0.116 and -0.242) and there were no differences (p>0.01) in the Hardy-Weinberg equilibrium. According to the analysis of molecular variance (AMOVA), most of the variation observed was within each group and not among groups, being confirmed by the Shannon index value (breeders = 0.477; offspring = 0.491). The genetic diversity in the offspring was preserved and the presence of multiple paternity and reproductive dominance was verified in 50 % of the offspring through the use of the semi-natural reproductive system.

La conservación de la variabilidad genética es prioritaria en lotes de peces usados en programas de repoblación de ríos, especialmente para especies amenazadas o en peligro de extinción como es el caso del Brycon orbignyanus. El objetivo del presente estudio fue estimar la diversidad genética y la contribución reproductiva de una progenie de B. orbignyanus usada en programas de repoblación, en un sistema reproductivo seminatural usando marcadores microsatélites. Se analizaron muestras de aleta caudal de 24 reproductores (12<img border=0 width=15 height=21 src="../../../../../img/revistas/agro/v44n2/a5s1.jpg"> y 12<img border=0 width=16 height=23 src="../../../../../img/revistas/agro/v44n2/a5s2.jpg">) y 95 larvas de su progenie. Reproductores y progenie mostraron dos a leí os, ausencia de alelos de baja frecuencia y una heterocigosis media de 0.470 y 0.510. El coeficiente Fis mostró que hubo ausencia de endogamia en los reproductores y progenie (-0.116 y -0.242) y no hubo diferencias (p>0.01) en el equilibrio de Hardy-Weinberg. De acuerdo con el análisis de varianza molecular (AMOVA), la mayor parte de la variación observada estuvo dentro de cada grupo y no entre los grupos, corroborado por el valor de índice de Shannon (reproductores = 0.477; progenie = 0.491). La diversidad genética en la progenie fue preservada y se verificó la presencia de paternidad múltiple y dominancia reproductiva en 50 % de la progenie mediante la utilización del sistema reproductivo seminatural.

Several ecological and climatic factors, especially those related to human activities, have been contributing to the disappearance of natural populations of piracanjuba (Brycon orbignyanus). Due to the importance of these fish to the ecosystems in which they are located and their qualities of fast growth and ability to adapt to controlled environments, producers have expressed increased interest in recent years in using this species, with particular aims of increasing production, and participation in conservation programs. In this study, strategies for the sustainable management of B. orbignyanus are idealized and discussed, with the goals of perfecting the reproductive, genetic, environmental and sanitary management of this species and suggestions for improving monitoring stocks maintained in captivity and natural populations. These strategies can be used as models for other migratory species threatened with extinction.

Diversos factores ecológicos y climáticos y especialmente aquellos relacionados con acciones humanas, han llevado a la desaparición de poblaciones naturales de piracanjuba (Brycon orbignyanus). Por la importancia en los ecosistemas en los cuales está ubicada y por sus cualidades de crecimiento rápido y adecuada adaptación a ambientes controlados, en los últimos años el interés de los productores en la utilización de esa especie ha aumentado, con el objetivo de la producción, la mejora económica y la participación en programas de conservación. Con el objetivo de perfeccionar el manejo e monitoreo reproductivo, genético, ambiental y de sanidad de lotes mantenidos en cautiverio y de poblaciones naturales de B. orbignyanus, estrategias de manejo sustentable de esa especie son idealizados y discutidos, pudiendo ser usados como modelo para otras especies migratorias amenazadas de extinción.

Environmental changes caused principally by human action have provoked reduction and even disappearance of several populations of fish. To minimize this impact stock enhancement programs are being implemented in several Brazilian states. However, without adequate evaluation, these programs can produce genetic changes in populations of native fish. Therefore the objective of this study was to analyze, with the RAPD molecular marker, the genetic diversity of Piaractus mesopotamicus stocks used in stock enhancement programs. One hundred twenty broodstocks at four fish farm stations located in the Sapopema (S), Cornélio Procópio (CP), Cambará (C), and Londrina (L) cities, in the Paraná state, Brazil, were analyzed. The results of genetic variability determined using the percentage of polymorphic fragments (S = 74.15 %; CP=78.80 %; C = 77.61 %; L=92.90 %) and the Shannon genetic diversity index (S=0.381, CP=0.422; C = 0.438; l=0.522) showed high genetic variability in all of the broodstocks. However, high genetic similarity was found between the S, CP, and P stocks possibly due to the founder effect since the stocks were founded with broodstocks collected in the Paraná River. The result was corroborated with Gst values and gene flow, which showed moderate genetic differentiation and high gene flow. The broodstock from L had a greater genetic distance from the other stocks because it was founded with broodstocks collected in the Paranapanema River. It was also confirmed that the broodstocks CP and C were the most genetically similar (genetic identity-GI=0.954) and the S and L broodstocks had less genes in common (GI=0.692). The L stock was the most distant of all the broodstocks.

Modificaciones ambientales derivadas principalmente de acciones humanas han causado la disminución y desaparición de varias poblaciones de peces. Para minimizar este impacto se aplican programas de repoblamiento en varios estados brasileños. Sin embargo, sin la adecuada evaluación estos programas pueden producir cambios genéticos en las poblaciones de peces nativos. Por tanto, el objetivo de este estudio fue analizar la diversidad genética de lotes de Piaractus mesopotamicus usados en programas de repoblamiento, mediante el marcador molecular RAPD. Se analizaron 120 reproductores en cuatro estaciones de piscicultura ubicadas en las ciudades de Sapopema (S), Cornélio Procópio (CP), Cambará (C) y Londrina (L), en el estado del Paraná, Brasil. Los resultados de variabilidad genética determinados usando el porcentaje de fragmentos polimórficos (S=74.15 %; CP=78.80 %; C = 77.61 %; L = 92.90 %) y el índice de diversidad genética de Shannon (S=0.381; CP=0.422; C = 0.438; L=0.522), mostraron una alta variabilidad genética en todos los lotes. Sin embargo, se encontró una alta similitud genética entre los lotes S, CP y P debido posiblemente al efecto fundador, ya que los lotes se fundaron con reproductores recolectados en el rio Paraná. Este resultado se corroboró con los valores de Gst y de flujo génico que mostraron una moderada diferenciación genética y un alto flujo génico. El lote de reproductores de L tuvo una mayor distancia genética con los otros lotes, debido a que se fundó con reproductores recolectados en el rio Paranapanema. También se constató que los lotes de reproductores CP y C fueron los más semejantes genéticamente (identidad genética-IG = 0.954) y que los lotes S y L presentaron menos genes en común (IG=0.692). El lote L fue el más distante de todos.