RESUMO
The highly migratory Atlantic bluefin tuna (ABFT) is currently managed as two distinct stocks, in accordance with natal homing behavior and population structuring despite the absence of barriers to gene flow. Larval fish are valuable biological material for tuna molecular ecology. However, they have hardly been used to decipher the ABFT population structure, although providing the genetic signal from successful breeders. For the first time, cooperative field collection of tuna larvae during 2014 in the main spawning area for each stock, the Gulf of Mexico (GOM) and the Mediterranean Sea (MED), enabled us to assess the ABFT genetic structure in a precise temporal and spatial frame exclusively through larvae. Partitioning of genetic diversity at nuclear microsatellite loci and in the mitochondrial control region in larvae spawned contemporarily resulted in low significant fixation indices supporting connectivity between spawners in the main reproduction area for each population. No structuring was detected within the GOM after segregating nuclear diversity in larvae spawned in two hydrographically distinct regions, the eastern GOM (eGOM) and the western GOM (wGOM), with the larvae from eGOM being more similar to those collected in the MED than the larvae from wGOM. We performed clustering of genetically characterized ABFT larvae through Bayesian analysis and by Discriminant Analysis of Principal Components (DAPC) supporting the existence of favorable areas for mixing of ABFT spawners from Western and Eastern stocks, leading to gene flow and apparent connectivity between weakly structured populations. Our findings suggest that the eastern GOM is more prone for the mixing of breeders from the two ABFT populations. Conservation of this valuable resource exploited for centuries calls for intensification of tuna ichthyoplankton research and standardization of genetic tools for monitoring population dynamics.
RESUMO
Numerosos estudios han sido enfocados a los ingredientes naturales para mantener la calidad y la vida útil de los alimentos. Los ingredientes biodegradables, tales como hidrocoloides y proteínas pueden ser utilizados para cubrir filetes de pescado con el objetivo de suprimir los cambios de calidad durante el almacenamiento en congelación. En la actualidad se han venido desarrollando empaques comestibles, como el glaseado con hidrocoloides, (gelatina, carragenina), que además de cumplir sus funciones como película protectora del alimento, son económicos, pueden ser ingeridos por el consumidor sin riesgo de toxicidad, ayudan a preservar las características organolépticas del producto, proporcionar características nutricionales y, por ser biodegradables contribuyen a la conservación del ambiente. El objetivo del presente estudio fue evaluar la incorporación de hidrocoloides al glaseado de lomos de atún como una alternativa de empaque. Cortes de atún fueron glaseados incorporándole soluciones de carragenina 0,05, y 0,15%, y gelatina al 0,5, 1%. Los cortes fueron de 15 cm3, congelados a -30ºC y glaseados con los tratamientos mencionados sumergiéndose la muestra de atún en las soluciones a 0 ºC por 30 segundos y luego almacenados a -10ºC por 0, 15 y 30 días. Los resultados del análisis proximal, las proteínas solubles, rancidez oxidativa, y color mostraron que todas las muestras glaseadas con hidrocoloides mantienen sus características y protege al lomo de atún ante la pérdida de humedad y retrasa la degradación de las proteínas. De igual manera la carragenina mostró un mejor desempeño como empaque a concentraciones de 0,05% en comparación con la gelatina.
Numerous studies have been focused to natural ingredients to maintain the quality and shell life of foods. Edibles coating, biodegradable ingredients, such as hydrocolloids and proteins can be used for coating fish with the purpose to suppress changes of quality during frozen storage. At the present time several developing of edibles packing, like glaze using hydrocolloids, (gelatin, carrageen, starch), that besides acts as protective film for food, they are economic, can be ingested by the consumer without toxicity risk, help to preserve organoleptics and nutritional characteristics of the product and, being biodegradable they contribute to the conservation of the atmosphere. The objective of the present study was to evaluate the incorporation of hydrocolloids in the glazing tuna process as alternative of packing, to enhance its physical and chemical characteristics. Samples of tuna was glazed incorporating to its solutions of carrageen at 0.05, 0,1 and 0.15%, and gelatin at 0.5, 1%. The samples were shaped as square (15 cm3), frozen al -30ºC and glazed incorporating hydrocolloids submerging the sample its solutions at 0 ºC by 30 seconds and storage at -10ºC by 0, 15 and 30 days. Proximal analysis results, soluble proteins, TBA, and color showed that all the samples glazed with hydrocolloids decrease deterioration of the tuna products respect to samples glazed without hydrocolloids; concluding that glazing adding hydrocolloids protects tuna for loss humidity and delays degradation of proteins. Moreover, carrageen shows to a better performance at the concentrations of 0.05% compared with the gelatin and the starch.