Fish species ecology in spanish freshwater ecosystems

The life strategies of the Iberian ichthyofauna, poor in species and with a high number of endemisms, are the result of the functioning of the aquatic systems (streams and reservoirs). The majorety of the species wager for iteroparity, high fertility, predominance of males over females and omnivorous feeding habits (short- chain trophic relationships). The fish assemblage is not very structured and depends on the autoecology of the species

Trophic morphoecology in the genus barbus (pisces, cyprinidae)

In this paper the morphological features and feeding habits of three coexisting Barbus species in the Tajo basin (Spain) were studied. Fifteen biometric measurements of each specimen were taken, then eleven morphological variables were calculated, and at the same time, the gastnc contents of each individual were analyzed. The results showed and important relationship of barbillon length, body form, branchial filter and buccal apparatus to size, distribution and food items. The exploitation of available resources in the reservoirs is discussed in the light of the discriminant body differences of the specie

Identification of the main factors in structuring rotifer community assemblages in ponds of Doñana National Park using the amino acid composition of the species

The use of the role of the species in the habitat (the niche), as an alternative to systematics for studying the processes that determine which and how many species live in a specific habitat (community assembly), is an approach that has been limited by the difficulties in the characterization of the niche. The aim of this study was to identify the determining factors in rotifers' assemblage in several ponds, using the amino acid composition (AAC) of the species as a fingerprint of the differential niche usage. We found that species with a similar AAC and, hence, with a similar trophic niche, spatially co-exist, showing that trophic-niche differentiation is not a main factor in structuring these lentic associations. The negative relationship between amino acid separation and spatial overlap among rotifer species can be considered as evidence that habitat filtering (abiotic factors) is the factor responsible for the assemblages.La utilización del papel de las especies en el habitat (el nicho), como alternativa a la aproximación sistemática, en el estudio de los procesos que determinan cuales y cuantas especies pueden coexistir en un determinado espacio (ensamble de comunidad), se ha visto limitada por las dificultades que existen para caracterizar el nicho. El objetivo de este estudio es identificar los factores determinantes de la asociación de rotíferos en distintas lagunas, utilizando la composición de aminoácidos (CAA) de las especies como un marcador del distinto uso del nicho. Encontramos que las especies con similar CAA, y por lo tanto, nicho trófico, coexisten espacialmente, lo que demuestra que la diferenciación trófica no es un factor estructurador de estas asociaciones leníticas. La relación negativa entre la separación de aminoácidos y el solapamiento especial entre las especies de rotíferos se puede considerar como una evidencia de que el filtro ambiental (factores abióticos) es el factor responsable de las asociaciones. Los resultados muestran que la salinidad y conductividad son las variables más importantes

The Iberian ichthyofauna : ecological contributions

The actual Iberian ichthyofauna is the result of the functioning of the aquatic systems and the human activities. For 27 years the Fish Ecology Research Group of Seville University has worked on understanding the complex relationships established around fish in different water systems and from differents approach scales (life strategies, population dynamics, structure and diversity of the communities, energy, etc.). The work carried out through those years has yielded a huge increase in the knowledge of our continental ichthyofauna. Now we are getting closer to understanding the Iberian epicontinental ecosystems and the ecology role of their fish, a basic need for management and conservation purposes.La actual ictiofauna ibérica es el resultado tanto del funcionamiento de los ecosistemas acuáticos como de las actividades humanas. Durante 27 años, el Grupo de Investigación de Ecología de Peces de la Universidad de Sevilla ha trabajado en la comprensión de las complejas relaciones que giran en torno a la ecología de los peces de nuestros diferentes ecosistemas epicontinentales, abordándolos desde distintas aproximaciones (estrategias de vida, dinámica de sus poblaciones, estructura y diversidad de sus comunidades, energéticas, etc). Los estudios llevados a cabo a lo largo de estos años han contribuido a incrementar el conocimiento de los ecosistemas acuáticos epicontinentales de la Península Ibérica y el papel ecológico de sus peces, conocimientos ambos básicos para el manejo y la conservación de los mismos

Trophic habits of the fish assemblage in an artificial freshwater ecosystem: the Joaquín Costa reservoir, Spain

The Joaquín Costa reservoir contains a mixed fish assemblage of native and exotic species. Feeding habits and feeding relationships of species in the fish assemblage were analysed over a one year cycle. Differences in diet composition were found both between species and within species among seasons. Food overlap and trophic similarity among species also showed seasonal variations. Cluster analysis differentiated four groups of predominant diet: (1) macroinvertebrates (trout and largemouth bass), (2) detritus (nase), (3) cladoceran crustaceans and (4) an omnivorous feeding regime, with large seasonal variations in food habits. Food of fish species included in groups 3 and 4 (roach, white bream, barbel, common and mirror carp) varied seasonally. Using graphical models of feeding strategies, similarity indexes, cluster and multivariate analyses based on the relative importance of food categories in the diet of the species, we illustrate that the fish assemblage showed food resource partitioning according to food habits and foraging habitats within the reservoir

Fish distribution in a reservoir with summer stratification

Studies were conducted to determine the spatial and vertical distribution of fish in a reservoir with summer stratification. Samples consisted of 24 h. capture with surface and bottom, trammel nets, over 18 stations and simultaneus echosoundings over 37 statiohs. The sarnpling was carried out rnonthl~d uring 1980 over the entire surface of the reservoir. For the calculation of the relative fish abundance the catch per unit effort (c.p.u.e.) is applied to the net results, and specific formulas to echo data. The results show a strong seasonal distribution pattern of the fish community. In spring and summer fish prevails in shallow zones with dense shore vegetation while in autumn and winter it shows an uniform distribution over all the reservoir. The vertical distribution is enfluenced by the limnologiccycle, with absence of fish in the hypolimnionduring the surnrner stratification due to oxygen scarcity

Estudio morfológico del aparato mandibular en cinco especies del género Chirostoma (Pisces : Atherinidae )

Se estudia morfológicamente 2 1 3 ejemplares del género Chirostoma: Ch. consocium (6 1 ) , Ch. chapalae (65), Ch. lucius (22), Ch. ocotlanae ( 5 1 ) y Ch. sphyraena ( 1 4) . Se midieron ocho variables biométricas de la mand¡bula inferior, diez de la superior y cinco variables complementarias en cada uno de los ejemplares. Se obtuvo una matriz de índices bucales, y se le aplicaron métodos comparativos (t-Student) y análisis multivariante (análisis de componentes principales y análisis de función discriminante escalonado). Se obtuvo la separación de las cinco especies, apreciándose valores máximos en Ch. lucius y Ch. sphyraena, para la superficie máxima bucal. Ch. consocium y Ch. ocotlanae obtienen valores más elevados para la densidad denticular de ambas mandíbulas y una mayor apertura bucal. Ch. chapalae, con una denticulación muy peculiar, posee la máxima protusión.\Ve found differences between the five species. Ch. lucius and Ch. sphyraena have the maximun buccal aperture surface . Ch. consocium and Ch. ocotlanae have the maximun denticular density of jaws and maximun buccal aperture. Finally, Ch. chapalae, with a ver y peculiar denticulation has maximun protusion