Abstract. An experiment was conducted to evaluate the effect of various levels of protein and dietary lipids on white snook (Centropomus viridis) performance. A 4 × 2 factorial design was used with 4 protein levels (40%, 46%, 52%, and 58%) and 2 lipid levels (10% and 13%), with 3 replicates per treatment. Fish with an initial weight of 14.80 ± 0.80 g were fed to apparent satiety 3 times a day for 6 weeks. Juvenile growth showed no significant differences among treatments. Feed efficiency was only affected by the protein level in the diet, and the best feed efficiency ratio was obtained with the 52% protein diets; the protein efficiency ratio was significantly lower with the 58% protein diets. The hepatosomatic index decreased with increasing protein content, and the peritoneal fat index increased with dietary lipid level. The condition factor was not affected by the dietary protein or lipid level. Hematocrit and total plasma protein were significantly higher at 40% protein; blood glucose and triglycerides were affected by both nutrients. It is concluded that juvenile C. viridis can be fed diets containing 40% protein and 10% lipids and a protein/energy ratio of 20.69 mg·kJ-1, under the experimental conditions of this study.

Resumen. Se llevó a cabo un experimento para evaluar el efecto de varios niveles de proteína y lípidos dietéticos en el rendimiento de juveniles de robalo blanco (Centropomus viridis). Se realizó un diseño factorial 4 × 2 con 4 niveles de proteína (40%, 46%, 52% y 58%) y 2 niveles de lípidos (10% y 13%), con 3 replicados por tratamiento. Los peces con un peso inicial de 14.80 ± 0.80 g se alimentaron a saciedad aparente 3 veces al día durante 6 semanas. El crecimiento de los juveniles no presentó diferencias significativas entre los tratamientos. La eficiencia alimenticia solo fue afectada por el nivel de proteína en la dieta, y la mejor tasa de eficiencia alimenticia se obtuvo con las dietas con 52% de proteína; el índice de eficiencia proteica fue significativamente menor con las dietas con 58% de proteína. El índice hepatosomático disminuyó al aumentar el contenido de proteína, y el índice de grasa peritoneal aumentó con el nivel de lípidos en la dieta. El factor de condición no fue afectado por el nivel de proteína o lípidos dietéticos. El hematocrito y la proteína total del plasma fueron significativamente mayores con las dietas con 40% de proteína; la glucosa y los triglicéridos en la sangre fueron afectados por ambos nutrientes. Se concluye que los juveniles de C. viridis pueden ser alimentados con dietas que contengan 40% de proteína y 10% de lípidos y una relación proteína/energía de 20.69 mg·kJ-1, bajo las condiciones experimentales de este estudio.

Resumen Introducción: El pez payaso (Amphiprion ocellaris) es la especie de pez más popular en el comercio de acuarios marinos; sin embargo, falta información sobre su fisiología digestiva durante la ontogenia larval, información valiosa necesaria para protocolos de diseño y manejo dietético. Objetivo: Caracterizar las enzimas digestivas tempranas de larvas de A. ocellaris. Métodos: Usamos tres homogenados (con 10 larvas cada uno) y extrajimos 10 muestras por tanque, justo antes de la eclosión hasta el día 38. Analizamos la actividad específica de proteasas ácidas y alcalinas, tripsina, quimotripsina, leucina aminopeptidasa y lipasa; e hicimos zimogramas de proteasas ácidas y alcalinas. Resultados: Detectamos todas las enzimas medidas en la eclosión. La actividad de proteasas ácidas incrementó hasta el día 38. Proteasas alcalinas, tripsina, quimotripsina, y leucina aminopeptidasa tuvieron el mismo patrón, con actividad máxima en el octavo día, decreciendo en el día 38. Hubo picos en la actividad lipasa a los ocho y 30 días. El zimograma ácido tuvo una banda única, apareciendo al octavo día. Se hallaron ocho proteasas alcalinas (154.2, 128.1, 104.0, 59.8, 53.5, 41.9, 36.5 y 25.1 KDa), con siete bandas al primer día, y todas las bandas entre el tercer y octavo día, bajando a dos bandas (41.9 y 25.1 KDa) al día 38. Conclusión: A. ocellaris tiene un estómago funcional al octavo día, y, al día 38, un patrón digestivo omnívoro con tendencias carnívoras.

Abstract Introduction: The Clown anemonefish (Amphiprion ocellaris) is the most popular fish species in the marine aquarium trade; however, there is a lack of information on their digestive physiology during larval ontogeny, valuable information needed for diet design and management protocols. Objective: To characterize the early digestive enzymes of A. ocellaris larvae. Methods: We used three pools (10 larvae each) and extracted 10 samples per tank, from just before hatching to the 38th day. We analyzed the specific activity of acid and alkaline proteases, trypsin, chymotrypsin, leucine aminopeptidase and lipase; and did acid and alkaline protease zymograms. Results: We detected all measured enzymes at hatching. Acid proteases increased in activity until the 38th day. Alkaline proteases, trypsin, chymotrypsin, and leucine aminopeptidase had the same pattern, and maximum activity on the 8th day, decreasing at the 38th day. Lipase activity peaked on the 8th and 30th day. The acid zymogram had a single band, appearing on the 8th day. A total of eight alkaline proteases were revealed (154.2, 128.1, 104.0, 59.8, 53.5, 41.9, 36.5 and 25.1 KDa), with seven bands on the 1st day and all bands from the 3rd to 8th day, decreasing at two bands (41.9 and 25.1 KDa) in the 38th day. Conclusion: A. ocellaris has a functional stomach on the 8th day, and, on the 38th day, a digestive omnivore pattern with a tendency to carnivory.

Abstract The objective of the present study was to evaluate the effect of different feeding regimens on productive and economic performance, and on the proximal-chemical composition of Nile tilapia. Four feeding regimens were designed considering the number of days fed per week, 7×0 (fed seven days a week), 6×1 (fed six days a week), 5×2 (fed five days a week) and 1×1 (alternating feeding, fed one day and not the next one). The period of dietary restriction lasted 36 days and subsequently fish were re-feeding for 24 days seven days a week. Growth was recorded every 12 days, estimating different productive parameters. An economic analysis taking into account the production costs was performed. Finally, the moisture, ash, lipid, protein and carbohydrate content of the Nile tilapia muscle was analyzed. At the end of the re-feeding period, a total wet weight compensation was observed for groups 6×1 and 5×2, and total length for groups 6×1, 5×2 and 1×1. The economic análisis recorded the highest increasing yields in group 5×2; while the group minimizing total variable costs was 1×1. The reduction in costs per unit of production between groups 7×0 and 1×1 was 15%. Chemical-proximal analysis revealed statistical differences for moisture content (7×0) and carbohydrate content (1×1). The groups 6×1 and 5×2 showed a total growth compensation, without negatively affecting muscle quality and/or final economic performance. The compensatory growth observed in the Nile tilapia allows to design feeding strategies to make its culture more efficient.

Resumen El objetivo fue evaluar el efecto de diferentes regímenes alimenticios en el desempeño productivo, económico y la composición química de la tilapia del Nilo. Se evaluaron cuatro regímenes alimenticios diseñados considerando el número de días alimentados por semana, 7×0 (alimentados los siete días), 6×1 (alimentados solo seis días), 5×2 (alimentados solo cinco días) y 1×1 (alimentación alternada, un día sí y un día no). El periodo de restricción alimenticia duró 36 días y posteriormente se realimentó siete días a la semana durante 24 días. Se registró el crecimiento cada 12 días, estimando diferentes parámetros productivos. Se realizó un análisis económico en función de los costos de producción. Por último, se analizó el contenido de humedad, cenizas, lípidos, proteínas y carbohidratos del músculo. Se observó una compensación total del peso húmedo para los grupos 6×1 y 5×2, y de longitud total para los grupos 6×1, 5×2 y 1×1. El análisis económico registró los mayores rendimientos crecientes en el grupo 5×2; mientras que el grupo 1×1 minimiza los costos variables totales. La reducción en costos por unidad de producción entre los grupos 7×0 y 1×1 fue de 15%. En el análisis químico se observaron diferencias significativas para el contenido de humedad (7×0) y de carbohidratos (1×1). Los tratamientos 6×1 y 5×2 permiten una compensación total del crecimiento, sin afectar negativamente la calidad del músculo y/o el rendimiento económico final. El crecimiento compensatorio observado en la tilapia del Nilo permite diseñar estrategias alimenticias para hacer más eficiente su cultivo.

Abstract The objective of this study is to evaluate the effect of β-agonists (BA), Zilpaterol Hydrochloride (ZH), and Ractopamine Hydrochloride (RH) on the biometric parameters and the muscle fiber thickness in Pelibuey lambs (n = 6). The control group was fed a standard diet (16% protein content and 12 MJ per day); treatment groups received a standard diet supplemented with ZH or RH for 37 days and was assessed presence of BA in samples of muscle tissues, and urine. The effect of Daily Weight Gain (DWG) and Food Conversion Rate (FCR) on muscle fiber thickness was determined by Scanning Electron Microscopy (SEM) and Digital Image Analysis (DIA). Results showed an increase of 30% in DWG in the ZH group, compared with RH. While FCR was lower in ZH (3.83) than in RH (4.85). In both BA treatments, the withdrawal time was sufficient to minimize drug concentration in meat. In contrast with the control group, muscle fiber thickness increased in BA treated groups (ZH = 69.2%, and RH = 15.6%). In conclusion, ZH displayed a higher carcass yield in Pelibuey lambs.

Resumen El objetivo de este estudio fue evaluar el efecto de los β-agonistas (BA), Clorhidrato de Zilpaterol (ZH) y el Clorhidrato de Ractopamina (RH) sobre los parámetros biométricos y el grosor de la fibra muscular en corderos Pelibuey (n = 6). El grupo control recibió una dieta estándar (DS) (16% de contenido de proteína y 12 MJ por día), mientras que los grupos de tratamiento recibieron DS+ZH o DS+RH durante 37 días. Se evaluó la presencia de BA en tejido muscular y orina, determinó el aumento de peso diario (DWG), la tasa de conversión de alimentos (FCR) sobre el grosor de la fibra muscular, mediante microscopía electrónica de barrido (SEM) y análisis de imagen digital (DIA). Los resultados mostraron 30% más en DWG en el grupo ZH, que en RH. Mientras que la FCR fue menor en ZH (3.83) que en RH (4.85). El tiempo de supresión aplicado fue suficiente para que los grupos ZH y RH no mostraran residuos. En contraste con el grupo de control, el grosor de las fibras musculares aumentó en los grupos tratados con BA (ZH = 69.2% y RH = 15.6%).

RESUMO: Buscamos por um impacto positivo de utilidade nas espécies invasoras como Pterygoplichthys spp. Foi avaliado o nível ótimo de substituição da farinha de sardinha (SM) pela farinha de Pterygoplichthys spp. (PML) em dietas práticas para tilápia do Nilo (Oreochromis niloticus). Foram utilizadas seis dietas experimentais; 50% PLM-50% SM, 60% PLM-40% SM, 70% PLM-30% SM, 80% PLM-20% SM, 90% PLM-10% SM e 100% PLM-0% SM. Em sistema de recirculação foram colocados 270 filhotes de tilápia machos (0.7 ± 0.1 g). As dietas foram triplicadas, o experimento durou 56 dias com amostragem a cada 14 dias, não houve diferença estatística para o crescimento. No final do experimento, foram determinados SGR, ADG, CF, WG, DFI, FCR e PER, não encontrando diferenças significativas (P> 0,05), embora tenha havido uma tendência indicando maior WG e PER na dieta 90% PLM-10% SM (93,56 ± 0,43% e 8,44 ± 1,18 g). A sobrevida foi superior a 90%, sem diferenças significativas. Além disso, não houve diferenças significativas na composição proximal de todo o peixe, enquanto o aparente coeficiente de digestibilidade de proteínas (81-90%) e lipídios (87-93%) também não mostrou diferenças significativas. Podemos concluir que o uso de 100% de farinha de Pterygoplichthys spp. pode substituir 100% de farinha de sardinha na alimentação de jovens O. niloticus sem afetar a sobrevivência, o crescimento, a composição química e a digestibilidade aparente dos nutrientes.

ABSTRACT: We search for positive utility impact on the invasive species Pterygoplichthys spp. The optimal level of replacement of sardine meal (SM) by Pterygoplichthys spp. meal (PLM) in practical feeds for fry of Nile tilapia (Oreochromis niloticus) was evaluated. We evaluated six experimental diets: 50% PLM-50% SM, 60% PLM-40% SM, 70% PLM-30% SM, 80% PLM-20% SM, 90% PLM-10% SM and 100% PLM-0% SM. In a recirculation system, 270 sex-reversed tilapia fry were used (0.7 ± 0.1 g). Diets were administered in triplicate and the experiment lasted 56 days with sampling every 14 days. There were no statistical differences in growth. At the end of the experiment, the SGR, ADG, CF, WG, DFI, FCR and PER were determined without significant differences (P > 0.05) between treatments, but there was a tendency that could indicated higher WG and PER in the 90% PLM-10% SM treatment (93.56 ± 0.43% and 8.44 ± 1.18 g, respectively). All survival rates were higher than 90% with no significant differences. Additionally, there were no statistical differences in the chemical composition of the whole fish, while apparent digestibility coefficients of protein (81-90%) and lipids (87-93%) also showed no significant differences. We concluded that 100% PLM can replace 100% SM in feeding fry of O. niloticus without affecting their survival, growth or chemical composition or the apparent digestibility of nutrients.

Abstract Bay snook (Petenia splendida) is a carnivorous cichlid species with excellent economic value in Southeast Mexico. Although this species presents an excellent potential for commercial aquaculture, the information about its nutritional, physiological, and reproductive metabolic pathways is meager. The current study focuses on the expression of glucose transporter 2 (glut2) in embryos and larvae at 5, 10, 15-, 20-, 25-, and 30-days post-hatch (dph) and in the liver, intestine, kidney, muscle, heart, testicle, gill, stomach, pancreas, and brain of adult fish. The partial sequence of glut2 was obtained, and specific qPCR primers were designed. In embryos, the expression was lower compared to larvae at 5, 15, and 20 dph. The highest expression in larvae occurred at 20 dph and the lowest at 25 and 30 dph. Maximum expression levels in adults occurred in the liver and intestine. Our results show that glut2 is expressed differentially across tissues of adult bay snook, and it fluctuates during larval development.

Resumen La mojarra tenguayaca (Petenia splendida) es una especie de cíclido carnívoro con excelente valor comercial en el sureste de México. A pesar de su potencial para la acuicultura, existe muy poca información sobre sus rutas metabólicas relacionadas con su nutrición, fisiología y reproducción. El presente estudio se enfoca en la expresión del transportador de glucosa (glut2) en embriones y larvas de 5, 10, 15, 20, 25 y 30 días post eclosión (dph) y en el hígado, intestino, riñón, músculo, corazón, testículo, branquias, estómago, páncreas y cerebro en peces adultos. Se diseñaron cebadores de qPCR específicos para glut2. La expresión en los embriones fue menor que en larvas a los 5, 15 y 20 dph. La expresión máxima en larvas se observó a los 20 dph y la mínima a los 25 y 30 dph. La expresión más alta en los adultos ocurrió en el hígado y el intestino. Nuestros resultados muestran que el gen glut2 se expresa de manera diferencial en los tejidos de adultos de la mojarra tenguayaca y su expresión fluctúa durante el desarrollo larvario.

ABSTRACT The development of native fish aquaculture represents an important alternative to mitigate ecological displacement generated by exotic fish. The introduction of native fish in polyculture systems with high commercial value fishes has provided a useful strategy for sustainable aquaculture development. The present study aims to provide information on tilapia, as an exotic species, and Dormitator latifrons, as a native species, in a duo culture not programmed as such. Using juveniles of Pacific fat sleeper D. latifrons leftovers from another experiment, we decide to analyze and report the biological feasibility of a duoculture system with this species and Nile tilapia (Oreochromis niloticus). Two hundred fifty organisms of each species were placed for 90 days in a concrete tank with a capacity of 50 m3 to evaluate the compatibility of these species. The biological variables measured were growth, survival, feed conversion rate, and protein efficiency. The findings suggest a good interaction between species, with adequate growths and a survival rate of 98%. No antagonistic behavior was observed during confinement, suggesting the duoculture of these species may represent a good alternative for tropical sustainable aquaculture.

ABSTRACT In the Southeast of Mexico, there are many native cichlids with commercial interest such as redhead cichlid (Vieja melanurus) and twoband cichlid (V. bifasciata), which have a great local demand and excellent meat quality. However, it is necessary to implement their culture based on nutrition studies and digestive biochemistry. This study’s objective was to characterize these two cichlids’ digestive proteases (pH, temperature, and inhibitors) through biochemistry techniques. Results showed that V. melanurus and V. bifasciata have a digestive capacity analogous to other omnivore fishes, where the optimal pH values of stomach proteases (4 and 2, respectively) and intestinal proteases (6 and 12, respectively), the optimal temperature of acid (35°C and 55°C, respectively) and alkaline proteases (45°C and 55°C, respectively) are quite similar. Both species presented high thermal and pH stabilities. Inhibition showed that V. melanurus is more sensitive to specific inhibitors for alkaline proteases than V. bifasciata. In conclusion, V. bisfasciata and V. melanurus have different digestive protease patterns. Both species can hydrolyze different protein ingredients to formulate a specific diet. Nevertheless, V. bifasciata is more resistant to the presence of inhibitors, which allow it to include vegetable proteins in its diet.

RESUMEN En el sureste de México, existen muchas especies de cíclidos nativos de interés comercial como el cíclido rojo (Vieja melanurus) y el cíclido de dos bandas (V. bifasciata), los cuales tienen una gran demanda local y tienen una excelente calidad de carne; sin embargo, es necesario implementar su cultivo con base en estudios de nutrición y bioquímica digestiva. El objetivo de este estudio fue caracterizar las proteasas digestivas (pH, temperatura e inhibidores) de estos dos cíclidos nativos mediante técnicas bioquímicas. Los resultados mostraron que V. melanurus y V. bifasciata tienen una capacidad digestiva similar a otros peces omnívoros, donde los valores óptimos de pH de proteasas estomacales (4 y 2, respectivamente) e intestinales (6 y 12, respectivamente), la temperatura óptima de proteasas ácidas (35°C y 55°C, respectivamente) y alcalinas (45°C y 55°C, respectivamente) son muy parecidas. Ambas especies presentaron alta estabilidad térmica y de pH. La inhibición mostró que V. melanurus es más sensible a inhibidores específicos de proteasas alcalinas que V. bifasciata. En conclusión, V. bisfasciata y V. melanurus tienen diferentes patrones de proteasas digestivas, pero ambas especies pueden hidrolizar diversos ingredientes proteicos para formular dietas específicas; sin embargo, V. bifasciata es más resistente a la presencia de inhibidores, lo que permitiría incluir proteínas vegetales en su dieta.

ABSTRACT Background: Bacteria of the genus Brucella yield the disease known as brucellosis (the most critical zoonosis in the world). Currently, 14 species are recognized, reported in marine mammals, amphibians, and commercial fish. In recent years, in the Eastern Basin, Brucella melitensis was detected in agricultural soil and the Crater Lakes’ water, so it was speculated whether B. melitensis could infect native ichthyofauna. Objective: Isolate and identify Brucella melitensis in the charal of La Preciosa Crater Lake (Poblana letholepis). Methods: The first isolation was carried out on agar-plate from soft tissues and identifying the microorganism through standard microbiological tests. Which was corroborated by PCR-PF, using reference strains, by amplifying the bp26 gene, specific for the genus Brucella. Results: B. melitensis was isolated in 66.66% of the samples studied n=60, the microbiological profiles were comparatively identical with the reference strains. The PCR test amplified the genus-specific gene bp26 with 1029 bp in 40% of the samples analyzed. Conclusions: The study generated the first isolation and identification report for Brucella melitensis in a native fish, which supports future studies to better understand this zoonotic disease and recognize the importance of native fauna in the transmission and permanence of brucellosis in natural aquatic environments.

RESUMEN Antecedentes: Las bacterias del género Brucella producen la enfermedad conocida como brucelosis (la zoonosis más importante del orbe). Actualmente se reconocen 14 especies, reportadas en mamíferos marinos, anfibios y peces comerciales, En los últimos años, en la Cuenca Oriental se detectó a Brucella melitensis en suelo agrícola y en el agua de los Lagos Cráter, por lo que se especulaba si B. melitensis tenía la capacidad de infectar a la ictiofauna nativa. Objetivo: Aislar e identificar a Brucella melitensis en el charal Poblana letholepis del Lago Cráter La Preciosa. Métodos: El primoaislamiento se realizó en placa-Agar a partir de tejidos blandos y la identificación del microorganismo a través de pruebas microbiológicas estándar. La identificación se corroboró por PCR-PF, utilizando cepas de referencia, mediante la amplificación el gen bp26, específico para el género Brucella. Resultados: Se aisló a B. melitensis en 66.66% de las muestras estudiadas n=60, los perfiles microbiológicos resultaron comparativamente idénticos con las cepas de referencia. La prueba por PCR amplificó el gen específico del género bp26 con 1029 pb en 40% de las muestras analizadas. Conclusiones: El estudio generó el primer reporte de aislamiento e identificación para B. melitensis en un pez nativo, el cual da soporte a futuros estudios para comprender mejor esta enfermedad zoonotica y reconocer la importancia de la fauna nativa en la transmisión y permanencia de la brucelosis en ambientes acuáticos naturales.

ABSTRACT Background: The legume Cannavalia ensiformis is an excellent source of energy, protein, vitamins and minerals to be used in animal production; however, it contains antinutritional factors (ANF), which limit its use for fishes. Goals: In this study 7 flours obtained from the processes of hydration, acid extraction, decorticating, cooking, germination, autoclaving and degreasing of the seeds of C. ensiformis were evaluated as means of elimination of ANF. Methods: The nutritional values of the meals were corroborated with proximal chemical analysis and in vitro digestibility, determining the degree of hydrolysis (GH%) of the flours of C. ensiformis obtained by pH STAT, the release of total amino acids (TAAL, μg mL-1) was calculated, using multienzymatic extracts of stomach and intestine of O.niloticus juveniles. Results: The acidic/alkaline GH values for cooked C. ensiformis flour were 0.76 ± 0.01% / 6.04 ± 0.37%, being significantly higher with respect to the other flours. The values of acidic/alkaline TAAL (µg mL-1) of this cooked flour (0.02 ± 0.006 / 0.40 ± 0.02) were significantly higher in the alkaline phase in relation to the other treatments. Conclusion: We detected that cooked meal of C. ensiformis, allow to be used as a source of protein in diets for Oreochromis niloticus.

RESUMEN Antecedentes: La leguminosa Cannavalia ensiformis es una excelente fuente de energía, proteína, vitaminas y minerales para ser utilizada en la alimentación animal; sin embargo, contiene factores antinutricionales (FAN), que limitan su utilización en la alimentación de peces. Objetivo: En este estudio se evaluaron 7 harinas obtenidas de los procesos de hidratación, extracción ácida, decorticado, cocción, germinado, autoclave y desgrasado de las semillas de C. ensiformis como medios de eliminación de FAN. Métodos: La calidad nutricional de las harinas fueron corroborados con análisis químicos proximales y digestibilidad in vitro, determinando el grado de hidrólisis (GH, %) de las harinas de C. ensiformis obtenidas mediante pH STAT, se calculó la liberación de aminoácidos totales (AALT, µg mL-1), utilizando extractos multienzimáticos de estómago e intestino de juveniles de O. niloticus. Resultados: Los valores de GH ácido/alcalino para la harina de C. ensiformis cocida fue de 0.76 ± 0.01%/ 6.04 ± 0.37%, siendo significativamente mayor con respecto a las otras harinas. Los valores de AALT ácido/alcalino (µg mL-1) de esta harina cocida (0.02 ± 0.006/ 0.40 ± 0.02) fueron significativamente mayores en la fase alcalina en relación a las otros tratamientos. Conclusión: Se detectó que la harina cocida deC. ensiformis, permite ser utilizada como fuente de proteína en dietas para Oreochromis niloticus.

Abstract: The design of specific feed based on digestive physiology, and an adequate feeding schedule, are important to reduce cannibalism and increase survival rate in larvae fish. The first objective of this study was evaluating growth, survival and cannibalism during tropical gar (Atractosteus tropicus Gill) larviculture, using four feeding schedules: CT (10 day co-feeding of Artemia nauplii and commercial trout feed), T1 (commercial trout feed), T2 (10 day co-feeding of Artemia nauplii and A. tropicus larvae designed feed) and T3 (A. tropicus larvae designed feed). The second objective was to determinate correlation between survival and cannibalism, using a linear regression model. We observed better growth and survival in the co-feeding treatments CT and T2. Cannibalism was observed in all treatments, with higher presence in T1 and T3 (treatments without Artemia nauplii co-feeding). It was observed a strong correlation between survival and cannibalism (r = -0.88, p < 0.05), demonstrating that cannibalism has a considerable effect on survival rate. We concluded that T2 represent the best alternative for A. tropicus feeding during larviculture, since they present better growth and less cannibalism.

Resumen: El diseño de dietas con base en la fisiología digestiva, así como un adecuado esquema de alimentación, permiten la disminución del canibalismo y el incremento de la supervivencia en la etapa larvaria de peces. Por lo anterior, el objetivo fue evaluar el crecimiento, supervivencia y canibalismo en la larvicultura del pejelagarto (Atractosteus tropicus Gill) bajo cuatro esquemas de alimentación: CT (co-alimentación con nauplio de Artemia por 10 días y dieta comercial de trucha), T1 (alimentación con la dieta comercial de trucha desde la apertura de la boca), T2 (co-alimentación con nauplio de Artemia y dieta diseñada para larvas de A. tropicus por 10 días) y T3 (alimentación con la dieta diseñada para A. tropicus desde la apertura de la boca), así como determinar la correlación entre el canibalismo y la supervivencia mediante un modelo de regresión lineal. Los mejores crecimientos y supervivencias se obtuvieron en los tratamientos T2 y CT. En todos los tratamientos se presentó canibalismo, siendo más alto cuando no se co-alimentó con nauplio de Artemia (T1 y T3). Se encontró una fuerte correlación (r = -0.88, p < 0.05) entre la supervivencia y el canibalismo, lo que demuestra que el canibalismo tiene efecto sobre la supervivencia. El tratamiento T2 representa la mejor alternativa para la larvicultura de A. tropicus, con mayor crecimiento y menor canibalismo.

ABSTRACT The effect of different lipid levels (10, 15, 20 and 25%) and oil sources (fish oil: FO and soybean lecithin oil: LO) on growth, survival, digestive enzymatic activity, gene expression acetyl CoA carboxylase (ACC1) and fatty acid synthase (FAS) of Mayan cichlid larvae Cichlasoma urophthalmus were evaluated by a bi-factorial design. The larvae were fed from hatching with eight different experimental isoproteic diets (45% protein) and a commercial diet for tilapia as a control diet. The results showed that larvae fed the LO15 diet had the highest growth in weight and total length and higher trypsin activity. The lowest values in FAS and ACC1 expression were obtained exclusively with the lipid type (soybean lecithin). It is concluded that the inclusion of soybean lecithin at a concentration of 15% allows the 100% replacement of fish oil in balanced feed for the culture of Mayan cichlid larvae.

ABSTRACT Wolf cichlid, Parachromis dovii, is a species with a high potential for aquaculture in Central America; however, the knowledge of the digestive physiology in larvae period is limited. For these reason, this study evaluated the changes on digestive enzymes (alkaline and acid proteases, trypsin, chymotrypsin, aminopeptidase, carboxypeptidase, lipases, amylases, and phosphatases) during early ontogeny by biochemical analysis. All digestive enzymes were detected at first feeding (6 days after hatching, DAH, 9.49 mm, 168 degree-days DD). Afterwards all enzymes reached two main peaks in activity at 14 or 22 DAH (15.10 mm, 364 DD and 20.83 mm, 550 DD, respectively). Later, there was a gradual decrease in activity for trypsin and acid and alkaline phosphatases until reach the lowest values at 41 DAH. In the case of acid proteases, chymotrypsin, aminopeptidase, carboxypeptidase, lipase and amylase, all activities reached their maximum values at the end of the larval period, except for alkaline proteases, which showed the maximum value at 14 DAH (15.10 mm, 364 DD). Parachromis dovii larvae have an early capability to hydrolyze exogenous food, agreeing with other carnivorous neotropical cichlid species, for this reason we proposed that the weaning process could begin at 14 DAH.

RESUMEN El guapote lagunero (Parachromis dovii) es una especie con un alto potencial para la acuicultura en la región de América Central; sin embargo, existe un conocimiento limitado sobre la capacidad digestiva en el periodo larval. Por este motivo, este estudio evaluó los cambios de las enzimas digestivas (proteasas alcalinas y ácidas, tripsina, quimotripsina, aminopeptidasa, carboxipeptidasa, lipasas, amilasas y fosfatasas) durante la ontogenia temprana mediante análisis bioquímico. Todas las enzimas digestivas analizadas se detectaron en la primera alimentación (6 días después de la eclosión, DAH, 9.49 mm, 168 día-grados DD). Después, todas las enzimas alcanzaron dos picos máximos a los 14 o 22 DAH (15.10 mm, 364 DD and 20.83 mm, 550 DD, respectivamente). Después las actividades tripsina, fosfatasas ácidas y alcalina disminuyeron a sus valores más bajos a los 41 DAH. En el caso de las proteasas ácidas y alcalinas, quimotripsina, aminopeptidasa, carboxipeptidasa, lipasa y amilasa, los niveles de actividad aumentaron y alcanzaron su máximo valor al final del período larvario, excepto las proteasas alcalinas, que mostraron su máximo valor a los 14 DAH (15.10 mm, 364 DD). Las larvas de P. dovii tienen una capacidad temprana para hidrolizar alimentos exógenos, lo que concuerda con otras especies de cíclidos neotropicales carnívoros, por lo que proponemos que el proceso de destete inicie a los 14 DAH.

ABSTRACT: Lipids requirement of tropical gar Atractosteus tropicus prejuveniles and juveniles was evaluated on growth, survival, chemical composition and apparent digestibility coefficient (ADC). Four semi-purified experimental diets (5, 10, 15 and 20% of lipids) were obtained with a mix of menhaden oil and soybean lecithin (2:1 ratio). Two trials were carried out, first with 600 prejuveniles of 0.5 g (35 days post-hatching, dph) for 56 days, and the second with 160 juveniles of 15 g (two-months-old) for 42 days. In the first trial, 15 (40.8 g) and 20% (40.2 g) lipid diets showed the best weight. Significant differences were obtained in condition factor (CF), daily lipid intake (DLI), hepatosomatic index (HSI), crude protein, ashes, nitrogen-free extract, moisture and ether extract between treatments. In the second trial, fish fed with the 10% lipid diet obtained the highest weight (89.1 g) compared with the other treatments. Significant differences were recorded for weight gain (WG), feed conversion ratio (FCR), specific growth rate (SGR), condition factor (CF), and lipid efficiency rate (LER). Also, significant differences were obtained in crude protein, ether extract, NFE, gross energy, apparent lipid ADC, protein ADC and dry matter ADC. The polynomial models applied to both trials indicated an optimum lipid requirement of 17% for 0.5 g juveniles and of 9% for 15.2 g juveniles.

Abstract: The sheepshead (Archosargus probatocephalus) is a priority species for mariculture development in southeastern México. The objective of the study was to reproduce in captivity two sheepshead batches, one in captivity for 12 months and another of wild breeders. The batch in captivity was formed by 36 organisms, in a water recirculation system with salinity of 10 psu, with the increase in their length and weight determined each month; in addition, sexual maturity was promoted by gradually increasing the salinity of the system up to 35 psu, after which spawning was induced with an intramuscular injection of 500 UI kg-1 of chorionic and serum gonadotropin hormone. On the other hand, 15 wild breeders were collected from the Alvarado Veracruz lagoon, inducing them to spawn in the same way. The average increase in length of the organisms conditioned to captivity was 0.064 ± 0.02 cm d-1 with average weight of 1.97 ± 0.4 g d-1, sexually maturing in the month of January. Both batches spawned; the eggs obtained had an average diameter of 817.3 ± 20.9 µm, average yolk sac volume of 243 ± 11 µL, average oil drop diameter of 203.5 ± 16.5 and average notochordal length of the eleuteroembryos of 1.65 ± 0.25 mm. It is possible to achieve maturation of the sheepshead in captivity, as well as obtain quality larvae from the induction of breeders in captivity and wild ones in the reproductive season.

Resumen: El sargo (Archosargus probatocephalus) es una especie prioritaria para el desarrollo de la maricultura en el sureste mexicano. El objetivo del estudio fue reproducir en cautiverio dos lotes de sargos, uno en cautiverio por 12 meses y otro de reproductores silvestres. El lote en cautiverio se formó por 36 organismos, en un sistema de recirculación de agua con salinidad de 10 psu, a los que se les determinó el incremento en longitud y peso cada mes, además se promovió la madurez sexual incrementando de forma gradual la salinidad del sistema hasta 35 psu, para luego inducir el desove con una inyección intramuscular de 500 UI kg-1 de hormona gonadotropina coriónica y sérica. Por otra parte, se colectaron 15 reproductores silvestres de la laguna de Alvarado Veracruz, induciéndolos al desove de la misma forma. El incremento promedio en longitud de los organismos acondicionados al cautiverio fue de 0.064 ± 0.02 cm d-1 con peso promedio de 1.97 ± 0.4 g d-1, madurando sexualmente en el mes de enero. Ambos lotes desovaron, los huevos obtenidos tuvieron un diámetro promedio de 817.3 ± 20.9 µm, volumen del saco vitelino promedio de 243 ± 11 µL, diámetro promedio de la gota de aceite de 203.5 ± 16.5 y longitud notocordal promedio de los eleuteroembriones de 1.65 ± 0.25 mm. Es posible lograr la maduración en cautiverio del sargo, así como, obtener larvas de calidad a partir de la inducción de reproductores en cautiverio y silvestres en la época reproductiva.