ABSTRACT The stressing effect of stocking density and rearing time was assessed on shrimp Penaeus vannamei reared intensively in floating cages. Juvenile shrimp were stocked in 9 m2 cages at 200, 250, and 300 ind m-2 for a 25-day grow-out period. Total soluble protein concentration, superoxide dismutase (SOD), and catalase (CAT) activities were used as stress indicators in shrimp muscle, hepatopancreas, and hemocytes. Twoway ANOVA showed that protein content in hepatopancreas significantly decreased as stocking rate increased (from 3.81 to 2.26 mg mL-1). Density and rearing time interacted significantly to determine SOD activity in muscle and hemocytes where the maximum activity occurred at the densest rate by the end of the study (10.21 and 122.41 U mg-1); CAT activity in hepatopancreas was significantly lower when the highest density (4.1 U mg-1) was used. Final shrimp weight (5.28-5.49 g), survival (90.2-91.9%), feed conversion ratio (0.75-0.78), specific (0.058-0.063), and absolute (1.17-1.30 g week-1) growth rates were not significantly affected by density, although yields varied significantly (0.99-1.49 kg m-2). To conclude, despite the stocking rate causing a stressing effect on shrimp, its antioxidant enzymatic activity prevented such development from negatively affecting shrimp growth, survival, feed conversion ratio, and production.

ABSTRACT In this work, we studied the digestibility, growth, blood chemistry, and enzyme activity of Nile tilapia (Oreochromis niloticus) juveniles (0.95±0.18 g) using different animal (fish silage meal, whey meal, bovine blood meal, and red crab meal) and plant (extruded bean, extruded chickpea meal, coconut paste, Jatropha curcas meal, and chickpea meal) dietary byproducts. Nine isocaloric diets (321.92±9.10 kcal g−1) were evaluated for 60 days. The highest digestibility of crude protein values for animal and plant sources were obtained for the whey (93.6) and extruded bean meal (90.5) diets, respectively. The final body weight was higher for the red crab and extruded chickpea meal diets, meanwhile the fish silage and red crab byproducts obtained the highest protein efficiency ratio. Hematocrit was similar among the diets of each byproduct source and presented correlation with growth parameters. The highest glucose, cholesterol, and triglyceride values were obtained for fish silage (138.0, 260.5, and 389.0 mg dL−1, respectively) and whey meal (174.5, 242.3, and 284.0 mg dL−1, respectively) groups. A positive correlation was found between the digestibility of crude protein of ingredients and chymotrypsin activity. Oreochromis niloticus is able to better utilize fish silage, whey, extruded bean, and extruded chickpea byproducts, adjusting its digestive physiology. Such ingredients can be used for formulating cheaper and efficient tilapia diets.

Our objective was to assess the quality of eggs and juvenile of Nile tilapia (Oreochromis niloticus) from broodstock of three commercial hatcheries (Hl, H2, and H3). Larval weight was significantly higher for H2 and H3 hatcheries (P < 0.05). After 45-day growth, weight of juveniles of H2 was higher, while specific growth rate was significantly higher for H1 and H2 (P < 0.05). After the ammonia stress test, no significant differences in mortality were found among larvae from the three hatcheries, although a positive relationship between carbohydrate content in eggs and juvenile mortality was observed (P < 0.05). After the salinity stress test, the lowest and highest mortality (P < 0.05) occurred respectively in tilapia larvae from the H1 (24.2%) and H3 (57.8%) hatcheries. We concluded that egg quality was not affected by tilapia broodstock from the three hatcheries studied, but differences were obtained for growth performance, carbohydrate content, and survival of juveniles when exposed to the salinity stress test. These three indexes should be considered as potential juvenile quality criteria for tilapia.

ABSTRACT The objective of our study was to assess the apparent digestibility of plant ingredients in diets for juvenile (50 g) and adult (220 g) Nile tilapia (Oreochromis niloticus). Dietary dry matter and protein apparent digestibility coefficients of four plant-derived feedstuffs (chickpea, maize, high-quality maize protein, and beans) were tested. The beans diet had the lowest apparent digestibility coefficient of dry matter (ADCDM) (69.41%), while no significant differences were detected in ADCDM among the other diets; ADCDM was significantly higher in adults compared with juveniles (77.02 vs. 73.76%). Apparent dry matter digestibility coefficient of ingredients (ADCI) was significantly higher in the chickpea (70.48%) and high-quality protein maize (71.09%) ingredients, and lower in the beans (52.79%) ingredient. Apparent dry matter digestibility coefficient of ingredients was significantly higher in juveniles compared with adults (72.56 vs. 56.80%). The protein digestibility of diet (ADCCP) was significantly higher in the reference diet (93.68%), while the lowest corresponded to the maize (87.86%) and beans (87.29%) diets. Significantly lower apparent digestibility coefficient of protein (ADCICP ) was obtained with the high-quality maize protein (59.11%) and maize (49.48%) ingredients, while higher ADCICP was obtained with the chickpea and beans ingredients (71.31 and 63.89%, respectively). The apparent digestibility coefficient of ingredient crude protein ADCICP was significantly higher in juveniles compared with adults (67.35 vs. 53.46). Digestibility is generally higher in juveniles, and we recommend using chickpea as an ingredient in diets for Nile tilapia.

Illegal catch of abalone and lobster along the west coast of the Baja California Peninsula (Mexico) was estimated from surveys conducted among fishers and data of custom duties on live lobster exported to the USA. We estimated that illegal catch of abalone amounts to 62 t yr-1 (27% of the commercial catch) and illegal catch of lobster amounts to 64 t yr-1 (5% of the commercial catch). The two methods used in this study to estimate the illegal lobster catch yielded similar and consistent results (4.7% of the legal catch when using survey data and 4.5% when using data on custom duties for 1989-2002). We conclude that the methods of estimation are useful and reliable because they are based on direct sources of information. The methods could be used for a bottom-up approach to estimate illegal catch.

Se estimó la captura ilegal de abulón y langosta en la costa oeste de la península de Baja California (México) a partir de encuestas entre pescadores e información sobre aranceles correspondiente a langosta viva exportada a los Estados Unidos. Se estimó que la captura ilegal de abulón asciende a 62 t año-1 (27% de la captura comercial) y la captura ilegal de langosta asciende a 64 t año-1 (5% de la captura comercial). Los dos métodos utilizados para estimar la captura ilegal de langosta arrojaron resultados similares y consistentes (4.7% de la captura legal usando datos de las encuestas y 4.5% usando información sobre aranceles de 1989 a 2002). Se concluye que los métodos de estimación son útiles y confiables porque se basan en fuentes directas de información. Los métodos pueden ser usados para un enfoque ascendente (bottom-up approach) en la estimación de captura ilegal.

The effect of the dietary protein level on growth and total body chemical composition of the native cichlid Bay snook (Petenia splendida), masculinized and non-masculinized, was studied. Five semi-purified diets with protein levels 35, 40, 45, 50 and 55% crude protein (CP) were formulated and evaluated by triplicate. Groups of 50 juveniles were each stocked in 70 L tanks and fed to apparent satiation for 42 days trial. At the end, weight gain (WG) (403.41%), body length (BL) (6.58 ± 0.10 cm) and specific growth rate (SRG) (1.67%/day) of the masculinized fish were obtained with the 45% CP diet, and they were significantly different (p = 0.002) from the other treatments. In the case of non-masculinized fish, the 45 and 55% CP treatments showed significant differences (p = 0.00001), with respect to other treatments, with a WG of 398 and 394%, SGR of 1.66 and 1.63%/day, protein productive value (PPV) of 28.91 and 29.21%, and feed conversion rate (FCR) of 1.23 and 1.08 respectively. Protein body composition for masculinized fish was different (p = 0.0001) only for fish fed 35% CP compared with fish at the beginning of the experiment. We conclude that the optimum protein requirement, estimated by the broken-line model for masculinized and non-masculinized P. splendida was 45 and 44.8% PC respectively.

Se evaluó el efecto del nivel de proteína sobre el crecimiento y composición química proximal del cíclido nativo tenguayaca (Petenia splendida) masculinizados y no masculinizados, para lo que se formularon cinco dietas semipurificadas con diferentes niveles de proteína cruda: 35, 40, 45, 50 y 55% PC, colocando 50 peces por tina (70 L) los cuales fueron alimentados a saciedad aparente por 42 días. Al final del periodo experimental, el mayor (p = 0.002) peso promedio (AW, 3.31 ± 0.46 g), longitud (BL, 6.58 ± 0.10 cm), ganancia en peso (WG, 403.41%) y tasa específica de crecimiento (SGR, 1.67%/día) en peces masculinizados se obtuvo para los alimentados con 45% CP. Los peces no masculinizados alimentados con las dietas de 45 y 55% CP fueron estadísticamente diferentes (p = 0.00001) en relación al WG (398 y 394%), SGR (1.66 y 1.63%/día), valor productivo de la proteína (PPV, 28.91 y 29.21%) y factor de conversión alimenticio (FCR, 1.23 y 1.08). La proteína corporal de los peces masculinizados fue estadísticamente diferente (p = 0.0001) para los peces alimentados con 35% CP comparados con los peces al inicio del experimento. Concluimos que el nivel óptimo de proteína estimado con el modelo de línea quebrada para los juveniles masculinizados y no masculinizados de P. splendida fue de 45 y 44.8% CP respectivamente.

Se diseñó, construyó y comprobó la aplicabilidad de un Índice de Evaluación Ambiental de Ecosistemas Acuáticos (IEAEA) basado en calidad físicoquímica, contenido de contaminantes en agua y sedimentos. Los criterios de calidad se fundamentan en investigaciones recientes y límites permisibles, y se establece cuáles contaminantes representan problemas potenciales en salud pública o ecosistemas acuáticos. La validación incluyó Análisis de Componentes Principales y Análisis de Sensibilidad. El IEAEA fue aplicado a resultados de 28 campañas de Tehuantepec, Oaxaca, México. Los Análisis de Sensibilidad se desarrollaron con los subíndices extremos y con la serie completa. La mayoría de los indicadores presentaron alta significación estadística. El modelo es robusto y los valores fluctúan cerca de la mediana. Se demostró que muestra sensibilidad a variaciones climáticas, número de variables y volumen de datos, por lo que se comprobó su aplicabilidad.

An Aquatic Ecosystems Environmental Evaluation Index (EEAEI) was designed and developed, based on physicalchemical features and pollutant contents in water and sediments. Its applicability was verified. The quality criteria are supported by recent research information and legal limits, and pollutants which represent potential problems to public health and aquatic ecosystems are established. Principal Component Analysis and Sensitivity Analysis were used as validation techniques. The Sensitivity Analyses were developed in the extreme subindices and in the complete data set. EEAEI was applied to the results of 28 campaigns of Tehuantepec, Oaxaca, Mexico. Most indicators displayed statistical significance. The model is powerful and the values fluctuate around the median. It was demonstrated that it is sensible to climate variations, number of variables and number of data inputs; therefore, its applicability was verified.

Desenhou-se, construiu e comprovou a aplicabilidade de um Índice de Avaliação Ambiental de Ecossistemas Aquáticos (IAAEA) baseado na qualidade físico-química, conteúdo de contaminantes na água e sedimentos. Os critérios de qualidade se fundamentam em investigações recentes e limites permissíveis, e estabeleceu-se: quais contaminantes representam problemas potenciais na saúde pública ou ecossistemas aquáticos. A validação incluiu Análise de Componentes Principais e Análise de Sensibilidade. O IAAEA foi aplicado a resultados de 28 campanhas de Tehuantepec, Oaxaca, México. As Análises de Sensibilidade se desenvolveram com os subíndices extremos e com a série completa. A maioria dos indicadores apresentou alta significação estatística. O modelo é robusto e os valores flutuam perto da média. Demonstrou-se que apresenta sensibilidade a variações climáticas, número de variáveis e volume de dados, pelo que se comprovou sua aplicabilidade.