ABSTRACT
Docosahexaenoic acid (DHA) is the most critical and least available omega-3 fatty acid in the Western human diet. Currently, the source of omega-3 long chain polyunsaturated fatty acids (LC-PUFA) is mainly dependent on wild fisheries, making this resource unsustainable in the foreseeable future. In recent years, a high rate of biosynthesis and accumulation of DHA has been discovered in a freshwater species (Chirostoma estor) belonging to the Atherinopsidae family. Interest in evaluating fatty acid composition in other members of the family has emerged, so this study compiles original data of flesh composition of eight atherinopsid species from freshwater and brackish environments, either wild or cultured. High levels of DHA (16 to 31%) were found in all analyzed members of the family, except in C. grandocule, independently of their habitat or origin. The analyzed species of the Jordani group (C. estor, C. promelas and C. humboldtianum) showed high DHA and low EPA levels (<0.5%) as previously reported for cultured C. estor. The low trophic niche of these atherinopsids and their fatty acid accumulation capabilities are factors that make these species noteworthy candidates for sustainable aquaculture.(AU)
O ácido docosahexaenóico (DHA) é o ácido graxo ômega-3 mais importante e menos disponível na dieta humana ocidental. Atualmente, a fonte de ácidos graxos poliinsaturados de cadeia longa ômega-3 (LC-PUFA) depende principalmente da pesca extrativista, tornando esse recurso insustentável em um futuro próximo. Nos últimos anos, uma alta taxa de biossíntese e acúmulo de DHA foi descoberta em uma espécie de água doce (Chirostoma estor) pertencente à família Atherinopsidae. Deste modo, surgiu o interesse em avaliar a composição de ácidos graxos em outros membros da família. Portanto, este estudo compila dados originais da composição de carne de oito espécies de aterinopsídeos de ambientes de água doce e salobra, selvagens ou cultivadas. Altos níveis de DHA (16 a 31%) foram encontrados em todos os membros da família analisados, exceto em C. grandocule, independentemente de seu habitat ou origem. As espécies analisadas do grupo Jordani (C. estor, C. promelas e C. humboldtianum) apresentaram altos níveis de DHA e EPA baixos (<0,5%), como relatado anteriormente para C. estor cultivado. O baixo nicho trófico desses aterinopsídeos e sua capacidade de acumulação de ácidos graxos são fatores que tornam essas espécies notáveis candidatas à aquicultura sustentável.(AU)
Subject(s)
Animals , Ecosystem , Aquaculture , Smegmamorpha/physiology , Fatty Acids , Fatty Acids, Omega-3 , Docosahexaenoic Acids , Fresh WaterABSTRACT
Menidia humboldtiana, a native species of Mexico, is a common inhabitant of local reservoirs. It represents a highly appreciated fish of economic importance in the central part of the country because of its delicate flavor. Trophic behavior of this species is important to understand the relationships with other fish species in reservoirs. With the aim to study this specific topic, the trophic spectrum, selectivity coefficient and overlap, were determined among different sizes of the Silverside M. humboldtiana. For this, both zooplankton and fish samples were taken during four different seasons of 1995. Zooplankton samples were taken through a mesh (125micron), and all organisms were identified to generic level. Fish were captured and grouped into standard length intervals per season, and the stomach contents were obtained and analyzed. Trophic interactions included the stomach contents analysis (Laevastu method), the coefficient of selection (Chesson) and the trophic overlap (Morisita index modified by Horn) between sizes. A total of 14 zooplankton genera were identified, of which Bosmina was the most abundant (29 625 ind./10L) followed by Cyclops (9 496 ind./10L), during the spring. Small size fishes (1-4.9cm) consumed high percentages of Cyclops in the spring (61.24%) and winter (69.82%). Ceriodaphnia was consumed by fish sizes of 3-10.9cm (72.41%) and 13-14.9cm (95.5%) during the summer; while in autumn, small sizes (1-4.9cm) ingested Mastigodiaptomus and Ceriodaphnia; Daphnia and Bosmina were consumed by fishes of 5-8.9cm and the biggest sizes (9-14.9cm) feed on Ceriodaphnia. M. humboldtiana makes a selective predation by the genera Ceriodaphnia, Daphnia, Mastigodiaptomus, Bosmina and Cyclops, depending on the size length interval. The trophic overlap was very marked among all sizes on spring, autumn and winter, unlike in summer fish of 1-2.9 and 11-12.9cm did not show overlap with other length intervals. M. humboldtiana is a zooplanktivore species, which performs a selective predation and a marked trophic overlap between the different fish sizes.
Menidia humboldtiana es una especie nativa muy apreciada por su delicado sabor. Se determinó el espectro trófico, selectividad y solapamiento trófico de ésta, durante 1995 (épocas del año), se obtuvieron muestras de zooplancton e identificaron a nivel genérico. Los peces capturados se agruparon en intervalos de longitud estándar para cada época. Se analizaron los contenidos estomacales (método volumétrico, Laevastu), selectividad (Chesson) y solapamiento trófico (Morisita). Se registraron 14 géneros de zooplancton; Bosmina el más abundante (29 625ind/10L) seguido por Cyclops (9 496ind/10L) ambos en primavera. Los peces pequeños (1-4.9cm) consumen a Cyclops en altos porcentajes en primavera e invierno, 61.24-69.82% respectivamente. Ceriodaphnia es consumida por peces de 3-10.9cm y de 13-14.9cm con 72.41-95.5% en verano; en otoño las tallas pequeñas ingieren a Mastigodiaptomus y Ceriodaphnia; Daphnia y Bosmina por peces de 5-8.9cm y los más grandes (9-14.9cm) a Ceriodaphnia. M. humboldtiana realiza una depredación selectiva por Ceriodaphnia, Daphnia, Mastigodiaptomus, Bosmina y Cyclops. El solapamiento trófico fue muy marcado entre todas las tallas en primavera, otoño e invierno, a diferencia en verano los peces de 1-2.9 y 11-12.9cm no registraron un solapamiento con otros intervalos de longitud. M. humboldtiana es una especie zooplanctófaga, que realiza una depredación selectiva y un marcado solapamiento trófico entre los intervalos de longitud.
Subject(s)
Animals , Food Chain , Feeding Behavior/physiology , Fishes/physiology , Body Size , Fishes/anatomy & histology , Fishes/classification , Gastrointestinal Contents , Mexico , SeasonsABSTRACT
Selectivity of zooplankton and trophic overlap between size Menidia humboldtiana fish (Atheriniformes: Atherinopsidae) in the reservoir Danxhó, Mexico. The Menidia humboldtiana silverside is considered one of the most important species in fisheries in some states of Mexico. Knowing the choice that this species exercises over its food gives us an understanding of the behavior of zooplankton in presence of zooplanktonic fish, and tells us if the silverside choose amongst bigger prey fish, and if there is competition for food between the native and introduced fish in the reservoir. The purpose of this study was to determine if M. humboldtiana selects its food, and in which genera, and to establish whether there was an overlap in the diet of the different sizes of silverside. The fish were catched with a 88 mm mesh net, in six sampling points during one year, from Danxhó (19°5´17" - 53´46" N, 99° 32´42" - 35´40" W) reservoir. Samples of filtered zooplankton were also taken with a 125 micron net. The analysis of stomach contents was carried out in fish grouped by regular size intervals during each season of the year, using the volumetric method and Chessons selectivity coefficient. To evaluate the trophic overlap between the different size groups, the Morisita index, modified by Horn, was used. The zooplankton community was represented by twelve genera: Mastigodiaptomus and Cyclops (Copepoda); Bosmina, Diaphanosoma, Daphnia, Ceriodaphnia, Moina, Alonopsis and Camptocercus, (Cladocera); Asplanchna, Conochillus and Filinia (Rotifera). Mastigodiaptomus was the most abundant throughout the year. The silverside consumed only four genera: Bosmina, Mastigodiaptomus, Daphnia and Ceriodaphnia; the group measuring 5 to 8.9 cm consumed a high percentage of Bosmina, Mastigodiaptomus and Daphnia, and a lesser percentage of Ceriodaphnia. The larger fish (9 to 10.9 cm) consumed only Mastigodiaptomus and Daphnia. In accordance with the selectivity values, the small and medium size silverside selected their prey, with more intensity on the genera Bosmina and Daphnia, while the bigger fish concentrated on Daphnia and Mastigodiaptomus. During spring, the silverside between 3 to 8.9 cm showed overlap in diet; in summer the bigger size group (7-10.9 cm) showed the overlap. In autumm the overlap ocurred in all sizes, and in winter it was shown only in the medium size fish (5-8.9 cm). Rev. Biol. Trop. 57 (1-2): 187-194. Epub 2009 June 30.
El charal Menidia humboldtiana es considerado como una de las especies de gran importancia en la industria pesquera de algunos estados de México. Es necesario conocer el efecto que esta especie ejerce sobre su alimento para saber si seleccionan las presas de mayor talla, si hay competencia por el alimento entre especies nativas e introducidas, y para comprender el comportamiento del zooplancton ante peces zooplanctófagos. Se determinó si M. humboldtiana selecciona su alimento, sobre qué géneros lo hace, y si existe traslape en la dieta entre las diferentes tallas. Los peces se recolectaron por medio de un chinchorro de 88 mm de abertura de malla, en seis estaciones de muestreo durante un año, en el embalse Danxhó, y una muestra de zooplancton fue recolectada por filtrado con una red de 125 µm. El análisis de los contenidos estomacales se realizó en peces agrupados en intervalos de longitud estándar para cada época del año, por medio del método volumétrico. Para evaluar el traslape trófico entre los diferentes intervalos de longitud, se utilizó el índice de Morisita modificado por Horn. El zooplancton estuvo representado por doce géneros: Mastigodiaptomus y Cyclops (Copepoda); Bosmina, Diaphanosoma, Daphnia, Ceriodaphnia, Moina, Alonopsis y Camptocercus (Cladocera); Asplanchna, Conochillus y Filinia (Rotifera). Durante la primavera, los charales de 3-8.9 cm presentaron un marcado traslape, para el verano fueron los grandes (7-10.9 cm), en otoño el traslape fue en todas las tallas, y en invierno solo las tallas intermedias (5-8.9 cm) lo presentaron.