Composición y superposición de dietas en cuatro especies de Diplectrum (Perciformes: Serranidae) en el Pacífico central mexicano

Analysis of diet composition and overlap in four species of the genus Diplectrum (Perciformes: Serranidae) in the Mexican Central Pacific. The information of trophic interactions among species is essential to understand ecosystem function. To assess this in four Diplectrum species, we analyzed the stomach contents of 397 individuals caught using shrimp trawling nets off the coasts of Jalisco and Colima, Mexico. Main food component of D. eumelum were fish of the Order Pleuronectiformes, followed by shrimps (Metapenaeopsis spp). D. euryplectrum feeds mainly on crustaceans, with stomatopods (Squilla mantoidea) as main food items followed by shrimps and brachyurans. Fish and polychaetes had a low representation in the diet of this species. D. labarum feeds mainly on crustaceans, mollusks and fish. The stomatopod Eurysquilla veleronis contributed to with a high diet percentage by weight, followed by shrimps (mostly Solenocera florae) and brachyurans, as well as the squid Lolliguncula diomedae. Fishes (Ophidion spp.) were also an important component of the diet of this species. The most common preys of D. rostrum were crustaceans, mollusks, polychaetes and fish. The squid Lolliguncula diomedae and fishes of genus Ophidion were also well represented in the diet. Diet breadth index yielded significant differences between species. The number of diet items varied from 16 in D. euryplectrum to 6 in D. eumelum. The average value of overlap (0.247) was not significantly different (p=0.118) from the expected one for a null model (0.174). The observed variance of the overlap index (0.071) was significantly higher (V=0.025, p=0.0004) than the value expected for a null model. Rev. Biol. Trop. 58 (4): 1189-1198. Epub 2010 December 01.

Para comprender las interacciones tróficas en un ecosistema, es imprescindible conocer bien la composición y superposición de las dietas de las especies que coexisten en un mismo hábitat y presentan una morfología general muy similar. Se analizaron los contenidos estomacales de 397 ejemplares de cuatro especies de Diplectrum, capturados con redes camaroneras frente a las costas de Jalisco y Colima, México. D. eumelum consumió principalmente peces del orden Pleuronectiformes, seguido por camarones del género Metapenaeopsis y estomatópodos. D. euryplectrum registró en su contenido estomacal, estomatópodos (Squilla mantoidea), seguido por camarones y braquiuros. D. labarum consumió crustáceos, moluscos y peces. El estomatópodo Eurysquilla veleronis registró un alto porcentaje, seguido por camarones (principalmente Solenocera florea) y braquiuros, así como el calamar dardo Lolliguncula diomedae. Los peces (género Ophidion principalmente) constituyeron un componente importante de la dieta de esta especie. En la dieta de D. rostrum se identificaron crustáceos, moluscos, poliquetos y peces. El calamar dardo Lolliguncula diomedae y los peces del género Ophidion tuvieron una alta representación. Se observaron diferencias significativas entre los índices de amplitud de dietas de las especies analizadas. El número de entidades consumidas disminuyó desde 16 en D. euryplectrum hasta seis en D. eumelum. El valor medio de superposición (0.247) no resultó significativamente diferente (p=0.118) del esperado para un modelo nulo (0.174). La varianza observada de los índices de superposición (0.071) fue significativamente mayor (V=0.025, p=0.0004) que el valor medio obtenido en la simulación basada en un modelo nulo.

Abundance variation of Porichthys margaritatus (Pisces: Batrachoididae) throughout thermic and bathymetric gradients in the central Mexican pacific

Three cruises, one in each of the main stream patterns in the area, were made on the central Mexican Pacific continental slope (May-June 1995, November 1995, and March 1996). Seven trawl sampling sites were defined per cruise, and in each site four bathymetric levels were sampled (20, 40, 60, and 80 m). During the warmest seasons, the highest abundance of Porichthys margaritatus was at 60 m. When the temperature of the bottom water was lower, in March 1996, the highest abundance of P. margaritatus moved towards 40 m. The depths with greatest abundance fluctuated between 18 and 21 degrees C, indicating a narrow temperature preference range. A Gaussian model was used to explain the relation between abundance and temperature.

Ictiofauna de la Bahía de Navidad, Jalisco, México / Ichthyofauna of the Navidad Bay, Jalisco, México

A check-list and the relative abundance of the ichthyofauna from Bahia de Navidad, Jalisco, Mexico is presented. This poorly known area of the eastern Tropical Pacific ocean is characterized by its great fish diversity. A total of 245 fish species (163 genera, 72 families) were collected during the 1994-1995 annual cycle. Vouchers were deposited in Centro de Ecologia Costera, Universidad de Guadalajara. The most important families in number of species were Carangidae (20 species), Haemulidae (20), Serranidae (17), Sciaenidae (13) and Lutjanidae (8); 20 species represented 85 and 80 of relative abundance and biomass respectively. Microlepidotus brevipinnis, Caranx caninus, Caranx caballus, Kiphosus analogus and Caranx sexfasciatus, were the dominant species. Most fish species collected in Bahia de Navidad have zoogeographical affinity with the Panamic Province (65), and in lesser proportion with the Eastern Pacific Ocean (19), Circumtropical (7), Mexican Province (5), Indo-Pacific Ocean (3) and Gulf of California (0.4). The great ichthyological affinity between the study area and the southern Gulf of California suggests an extension of the of Gulf southern limit.