Common snook Centropomus unidecimalis is an important commercial and fishery species in Southern Mexico, however the high exploitation rates have resulted in a strong reduction of its abundances. Since, the information about its population structure is scarce, the objective of the present research was to determine and compare the age structure in four important fishery sites. For this, age and growth of common snook were determined from specimens collected monthly, from July 2006 to March 2008, from two coastal (Barra Bosque and Barra San Pedro) and two riverine (San Pedro and Tres Brazos) commercial fishery sites in Tabasco, Mexico. Age was determined using sectioned saggitae otoliths and data analyzed by von Bertalanffy and Levenberg-Marquardt among others. Estimated ages ranged from 2 to 17 years. Monthly patterns of marginal increment formation and the percentage of otoliths with opaque rings on the outer edge demonstrated that a single annulus was formed each year. The von Bertalanffy parameters were calculated for males and females using linear adjustment and the non-linear method of Levenberg-Marquardt. The von Bertalanffy growth equations were FLt=109.21(1-e-0.21(t+0.57)) for Barra Bosque, FLt=94.56(1-e-0.27(t+0.48)) for Barra San Pedro, FLt=97.15(1-e-0.17(t+1.32)) for San Pedro and FLt=83.77(1-e-0.26(t+0.49)) for Tres Brazos. According to (Hotelling’s T2, p<0.05) test growth was significantly greater for females than for males. Based on the Chen test, von Bertalanffy growth curves were different among the study sites (RSS, p<0.05). Based on the observed differences in growth parameters among sampling sites (coastal and riverine environments) future research need to be conducted on migration and population genetics, in order to delineate the stock structure of this population and support management programs. El robalo blanco Centropomus undecimalis representa un ingreso monetario significativo y un recurso alimentario para todas las comunidades rurales cercanas a su distribución. Se determinó la edad y crecimiento de esta especie. Los organismos se recolectaron mensualmente en los desembarcos de la pesca artesanal de las cooperativas de mayor contribución en la zona costera (Barra Bosque y San Pedro) y ribereña (San Pedro y Tres Brazos) entre julio 2006 y marzo 2008. La edad se determinó mediante otolitos seccionados. La edad estimada fue de 2 a 17 años. Mensualmente se estableció la formación anillos opacos y traslúcidos. Para ambas zonas de estudio agrupadas, se validó el retrocálculo por comparación de tres métodos (Fraser-Lee, Dahl-Lea y Whitney-Carlander), se encontraron diferencias significativas (ANCOVA, p<0.05) entre el promedio de la longitud observada y la longitud retrocalculada. Las constantes de la ecuación de von Bertalanffy fueron calculadas para cada sexo y combinados, se empleó el método no lineal de Levenberg-Marquardt’s. La edad estimada para el robalo blanco fue de 2 a 17 años. Se encontraron diferencias significativas en el crecimiento entre sexos (T2 Hotelling, p<0.05). Los parámetros de crecimiento para ambos sexos fueron, zona costera: Barra Bosque Lft=109.21(1-e-0.21(t+0.57)), Barra San Pedro Lft=94.56(1-e-0.27(t+0.48)), y para la zona ribereña: San Pedro Lft=97.15(1-e-0.17(t+1.32)) y Tres Brazos Lft=83.77(1- e-0.26(t+0.49)). Se encontraron diferencias significativas en las curvas de crecimiento de von Bertalanffy entre las poblaciones comparadas (RSS, p<0.05).

Pseudomonas fluorescens is a bacterium that has been identified as a significant pathogen in fish from the aquaculture industry. However, the clinical signs and changes caused by the disease have not been studied well yet. This study aimed to determine the survival, morphological, and histopathological changes in zebrafish (Danio rerio) in an experiment involving 180 fish (0.250 ± 0.05 g). The organisms were inoculated intraperitoneally at four bacterial concentrations 1.5 × 10⁶, 1.5 × 10⁷, 1.5 × 10⁸, and 1.5 × 10⁹ CFU mL⁻¹ with respective control groups. Results showed that cumulative mortality at 96 h post infection (hpi) was 0% (1.5 × 10⁶ CFU mL⁻¹), 0% (1.5 × 10⁷ CFU mL⁻¹), 6.66% (1.5 × 10⁸ CFU mL⁻¹), and 33.33% (1.5 × 10⁹ CFU mL⁻¹). The survival curves were not statistically different (p = 1.000). Corresponding to differences between clinical signs and concentrations for 24 hpi (p = 0.7576) there were no significant differences, for 48 hpi statistical differences were obtained (p = 0.0008), while for 72 hpi (p = 0.8922) and 96 hpi (p = 0.333) they were not observed. The predominant clinical signs were anorexia, lethargy, erratic swimming, and peritoneal haemorrhage. The acute septicemic clinical form was determined. Histological analyses showed that the gills, liver, and spleen were infected and had severe pathological alterations. These findings indicate that the zebrafish is susceptible to P. fluorescens infection.

Las almejas de agua dulce son organismos filtradores y bioindicadores de la salud del ecosistema acuático. Su distribución es cosmopolita, pues es un grupo muy diverso en toda la costa oriental de Norte, Centro y Sudamérica. En el sureste México se conocen nueve géneros y doce especies, y en el bajo Usumacinta cinco especies y cinco géneros. Estos organismos presentan sexos separados, aunque algunos son hermafroditas.

Herbaceous plants have attracted increasing attention in the aquaculture industry for their beneficial effects on the growth, health, and physiology of several fish species. Matali (Tradescantia zebrina) is a medicinal herb widely distributed in southeastern Mexico and recognized for its diverse pharmacological properties. This study aimed to evaluate the effects of T. zebrina on growth performance, cytotoxicity, and digestive morphology in the two-band cichlid (Vieja bifasciata), a native species with aquaculture potential. Cytotoxicity of the aqueous extract of T. zebrina was assessed using Artemia nauplii exposed for 24 h to serial dilutions ranging from 100 to 0.78 mg mL-1. Subsequently, diets supplemented with 0% (T1), 5% (T2), 10% (T3), and 15% (T4) T. zebrina were evaluated for their effects on growth performance and digestive morphology in V. bifasciata over a 45-day feeding trial. The results demonstrated that the aqueous extract of T. zebrina was non-toxic, suggesting that its inclusion in fish diets is safe. The highest weight gain was recorded in T2 (2.28 ± 0.43 g), whereas the greatest total length was observed in T3 (5.07 ± 0.04 cm). Survival was highest in T4 (100%). Based on weight gain, specific growth rate, and feed conversion ratio, T2 was identified as the most effective treatment for promoting growth (P < 0.05). In addition, dietary supplementation with T. zebrina produced modifications in digestive morphology. Overall, the inclusion of 5-10% T. zebrina in the diet can serve as a feed supplement without adversely affecting V. bifasciata growth. Further studies involving gene expression, immunological responses, and enzymatic activity are recommended to validate additional potential benefits of T. zebrina in aquaculture.