Time filter

Source Type

Vilagarcía de Arousa, Spain

Sanchez-Hernandez J.,University of Santiago de Compostela | Cobo F.,Station of Hydrobiology Encoro do Con
Acta Ichthyologica et Piscatoria | Year: 2012

Background. The northern Iberian chub Squalius carolitertii (Doadrio, 1988) is a small endemic cyprinid inhabiting the rivers of the Iberian Peninsula. The knowledge of feeding patterns is essential to understand the ecological role of fish populations, helping to the development of conservation and management plans. The aim of the present study was to analyze the ontogenetic dietary shifts and food selection of S. carolitertii, contributing to knowledge of the feeding behaviour of this fish species. Materials and methods. Diet composition of S. carolitertii was compared to benthos and drift composition in a river of Central Spain (Ávila, River Tormes) using selectivity indices of Ivlev and Savage. The age of 57 S. carolitertii collected in August 2010 was determined by scale reading and by length frequency analyses (LFA) with the Petersen method. Maximum length of benthos, drift and prey invertebrates was measured for each item to establish whether prey-size selection depends upon the size-frequency distribution of available prey. Results. Detritus were found in 33 fish (57.9% of occurrence). Nymphs of Baetis spp. were the most abundant prey (46.6%) and were identified in the 49.1% of the stomachs. Moreover, Baetis spp. was selected positively from the benthos and drift by all age classes. Abundant potential prey items such as Epeorus spp. in the benthos and Simuliidae in the drift were negatively selected. Individuals without detritus in the gut contained more animal prey items than individuals with a dominance of detritus, and the frequency of occurrence of detritus decreased with the age. Mean prey size increased with fish size (r = 0.646, P < 0.001). Conclusion. Age-related diet shifts occur at three different levels: (1) frequency of occurrence of detritus decreases with fish age; (2) prey selection varied with fish age; and (3) mean prey size increased as fish size increased. The rejection of Epeorus spp. and Simuliidae suggests that other factors, apart of prey abundance, including sitespecific prey accessibility, prey size, energetic selection criteria and prey preference of fishes play an important role in feeding behaviour of S. carolitertii. Prey-size selection is probably dependent on the size-frequency distribution of the available prey. Source

Sanchez-Hernandez J.,University of Santiago de Compostela | Servia M.J.,University of La Coruna | Vieira R.,Station of Hydrobiology Encoro do Con | Barca-Bravo S.,University of Santiago de Compostela | Cobo F.,University of Santiago de Compostela
Limnetica | Year: 2012

Brown trout is an important angling species worldwide, and its morphology, population structure and genetics can be highly variable from one location to another. In this study, we provide data for the establishment of reference range values for several population and growth parameters of brown trout in the Cantabrian-Atlantic siliceous rivers of Galicia (NW Spain). Additionally, this study tests the hypothesis that the population and growth parameters differ among sections of rivers with different exploitation statuses (unexploited, exploited-regulated and exploited-open sections). Our study revealed that such population parameters as biomass and production were higher in unexploited sections, but the differences in growth among the sections with different angling regulations were not consistent. The findings of this study are discussed in light of the present knowledge on the status of trout fisheries, as it is essential for the development of management plans. Additional studies are needed to clarify whether the differences in growth can be correlated to the angling regulations. © Asociación Ibérica de Limnología, Madrid. Source

Cobo F.,Station of Hydrobiology Encoro do Con | Cobo F.,University of Santiago de Compostela | Sanchez-Hernandez J.,Station of Hydrobiology Encoro do Con | Sanchez-Hernandez J.,University of Santiago de Compostela | And 2 more authors.
Hydrobiologia | Year: 2013

Sewage pollutants may impair growth or survival of the freshwater biota, though animals might benefit from the extra food availability as production increases. We examined biochemical (muscle glycogen), morphological (condition factor and hepatosomatic index), and diet biomarkers in brown trout for evaluating the effects of chronic exposure to organic pollution. Trout were collected at three locations: ST1 downstream of a trout farm, ST2 affected by the effluents of a wastewater treatment plant and ST3, the reference site. Individuals at polluted sites showed high hepatosomatic index, although no differences were found between ST2 and ST3 for the condition factor. A significant reduction was detected in the levels of muscle glycogen of individuals captured at polluted sites. Moreover, trout diet in these rivers was dominated quantitatively by Chironomidae and Simuliidae, in contrast with the diverse diet of individuals at ST3. Remarkably, individuals at polluted sites showed high stomach fullness and energy gut values, which might be considered as a case of hyperphagia. Our findings suggest that food surplus in organic enriched sites, in the form of high densities of macroinvertebrates, provide an environment similar to that of domesticated animals, where individuals might adopt less energetically costly behavioural strategies to ingest more food. © 2012 Springer Science+Business Media Dordrecht. Source

Nachon D.J.,University of Santiago de Compostela | Sanchez-Hernandez J.,University of Santiago de Compostela | Vieira-Lanero R.,Station of Hydrobiology Encoro do Con | Cobo F.,University of Santiago de Compostela
Marine and Freshwater Research | Year: 2013

In order to contribute to a better understanding of feeding behaviour of adult twaite shad, Alosa fallax, in freshwater, we studied the stomach content composition of 147 A. fallax during their upstream spawning migration in the River Ulla (Galicia, NW Spain). The diet composition included 34 types of prey, aquatic invertebrates being the most important food. The present study is, to the best of our knowledge, the first record of A. fallax feeding on potamodromous Pseudochondrostoma duriense. © CSIRO 2013. Source

Discover hidden collaborations