Do advantages in resource exploration lead to better body condition (original) (raw)
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Diet of a catfish before and after damming of the salto caxias reservoir, iguaçu river
Brazilian Archives of Biology and Technology, 2007
This study evaluated the diet of Pimelodus sp., before and after damming of Salto Caxias, (waterfall in the Iguaçu river), as well spatial and ontogenetic diet shift. Surveys were carried out from March 1997 to February 1998 (before damming) and from April 1999 to January 2000 (after damming) inside the reservoir and adjacent tributaries. Stomach contents analysis of 682 specimens revealed omnivory with high degree of trophic opportunism to this species. Analysis of variance (three way ANOVA) for scores produced from Detrended Correspondence Analysis (DCA) yielded a significant interaction between the damming phases and size of the individuals (juveniles and adults) (F = 4.68; P = 0.04). After damming, adults exploited mainly fish, whereas the juveniles fed mostly on plants, dipterans larvae and scales at different sites. From significant differences in the ordination among the factors considered, it could be inferred that the diet of Pimelodus sp. was influenced by the formation of...
Neotropical Ichthyology, 2016
The increase in abundance of small-sized fishes is common after a reservoir is formed. There is an increase in the consumption of fish, from typically piscivorous fish to opportunistic species that take advantage of abundant resources. This study aims to evaluate the effects of diet changes induced by damming on the feeding activity and condition factor of typically piscivorous (Hoplias aff. malabaricus and Oligosarcus longirostris) and opportunistic (Astyanax lacustris (ex Astyanax altiparanae) and Pimelodus britskii). Sampling was conducted before and after the impoundment in the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Stomach contents were analysed by the volumetric method. Feeding activity and body condition were inferred by the mean stomach repletion index and the mean condition factor. Typically piscivorous species presented a general tendency of decreased feeding activity and increased condition factor, while opportunistic species, presented a decrease in condition and feeding activity in the most affected sites. The increase in the condition factor of piscivorous fish suggests that these species benefit by the increased abundance of small size prey fish. Some opportunist species that do not have adjustments for the piscivorous diet, regardless of the intensity of consumption and resource availability, can suffer negative reflex when adopting a piscivorous diet. O aumento na abundância de peixes de pequeno porte é comum logo após a formação de um reservatório, levando a um aumento no consumo de peixes, tanto por peixes piscívoros como oportunistas que se aproveitam do recurso abundante. Esse estudo visa avaliar os efeitos da mudança de dieta induzida pelo represamento na atividade alimentar e condição nutricional, tanto de espécies piscívoras (Hoplias aff. malabaricus e Oligosarcus longirostris) quanto de espécies oportunistas (Astyanax lacustris (ex Astyanax altiparanae) e Pimelodus britskii). Para tanto, foram realizadas amostragens nas fases pré e pós-represamento no rio Iguaçu na região de Salto Caxias, Paraná, Brasil. Os conteúdos estomacais foram avaliados pelo método volumétrico. A atividade alimentar foi determinada pelo índice de repleção estomacal e a condição nutricional através do fator de condição relativo. As espécies tipicamente piscívoras apresentaram, em geral, incremento no fator de condição e queda na atividade alimentar e a espécie mais oportunista apresentou queda no fator de condição e índice de repleção nas regiões mais afetadas pelo represamento. O aumento no fator de condição de espécies piscívoras sugere que estas se beneficiam pelo aumento de abundância das espécies de pequeno porte. Enquanto espécies que não possuem adaptações para uma dieta piscívora, independente da intensidade de consumo e disponibilidade desse recurso, podem sofrer reflexos negativos em sua condição nutricional, em detrimento da ausência de pré-adaptações à piscivoria.
Acta Oecologica, 2003
The closure of a dam and the following inundation of large areas constitute a major perturbation of the river ecosystem. Under tropical conditions, one of the first constraints imposed on organisms in the new ecosystem is the trophic one. This work aims at determining which feeding strategies are the most successful for the development of fish populations in such a transforming environment. In addition, it will examine the change in food resource used by the assemblages. Soon after the closure of the Petit-Saut Dam, French Guiana, higher plants and terrestrial invertebrates constitute the main resources for the fish assemblage but resources of aquatic origin subsequently progressively substituted them. Generalists, already numerous in the river, were the most successful in the first stage of reservoir formation. However, over time, specialist species (detritivores, piscivores, invertivores and herbivores) became more important in the assemblage and the trophic structure became more balanced. These results support the hypothesis of greater colonization ability for generalists and of their decline when competition takes place.
Neotropical Ichthyology, 2014
The present study investigated energy allocation patterns in three fish species from the family Hemiodontidae (Argonectes robertsi, Hemiodus microlepis, and Hemiodus unimaculatus), before and after the construction of Lajeado Dam, Tocantins River, Amazon basin. Changes in the use of energy (between somatic and reproductive processes) were indirectly evaluated by means of temporal variations in fish body condition, feeding activity, visceral fat storage, and reproductive effort. Fish were collected from October 1999 to September 2004, in periods that preceded and followed the construction of the dam. We recorded significant changes in all ecological traits for the three analyzed species (for males and females). In general, there was an intense reduction in reproductive activity after river damming, whereas visceral fat and body condition increased consistently. In contrast, there was no clear trend in feeding activity (i.e., stomach weight), with little changes in species diet during...
Fisheries Research, 2005
A field study of age, growth and mortality of the “boga”, Leporinus obtusidens (Valenciennes, 1847) was carried out in the Yacyretá Reservoir, High Paraná River, Argentina. We compared age-structure, length–weight relationships and condition factor coefficients in phases previous (1990–1994) and subsequent (1995–1998) to the reservoir filling. In addition, we estimated total and natural mortality, as well as the growth and yield parameters for the whole study period. Comparisons were carried out in four sampling points within the river main channel. Fish were sampled monthly with nine gillnets ranging from 40 to 160 mm of total mesh opening (opposed knots). A scale study showed an age range comprised between 1 and 13 years, with ages 4 and 5 the most abundant before reservoir filling, whereas ages 2 and 3 were more frequent afterward. The weight–standard length relationship showed a higher growth during the second phase of reservoir filling. Maximum condition factor was registered before the spawning period (August and September), being higher after the impoundment, and particularly in the sampling site located within the reservoir. The von Bertalanffy growth coefficient, K, reached 0.12 in both sexes, while the asymptotic length, L∞, was 578 and 547 mm, in females and males, respectively. Natural mortality according to Pauly's equation reached 0.178 year−1, and the total mortality was 0.36 year−1. The Beverton and Holt yield per recruitment (Y/R) was estimated as 246.54 g, with a maximum sustainable yield of 248.00 g. This result suggests that the species had higher condition after impoundment and is fished near its maximum capacity in the reservoir.
2015
Length-weight relationship (LWR) and condition factor of seven fish species from the Temengor Reservoir, Peninsular Malaysia were analyzed. A total of 1155 individuals belonging to two families namely Nandidae and Cyprinidae were measured and weighed. The most highly represented family was Cyprinidae which comprised six species. Among these seven species, three species generally showed positive allometric growth, two species showed isometric growth and the other two species showed negative allometric growth. The exponent b value of LWR ranged between 2.601 (Oxygaster anomalura) and 3.157 (Cyclocheilichthys apogon) with a mean of 2.983. The lowest mean condition factor, K was recorded in O. anomalura (0.648 ± 0.131) while the highest value was observed in Pristolepis fasciata (2.194 ± 0.153). This study has contributed to the knowledge of fish populations in this economically important area that could assist fishery management scientists in carrying out future ecological studies in l...
Iheringia. Série Zoologia, 2016
Food flexibility and omnivory are important features pronounced in Neotropical freshwater fish species, particularly for Astyanax species. Traditionally most fish diet resources are known to be originated in the aquatic environment, however recent studies have pointed to the importance of allochthonous sources. Besides, the colonization of macrophytes, common at several tropical reservoirs, may enhance insectivory in fish diet expanding or concentrating the area of available resources for feeding. Here we employed stomach contents analysis of two sympatric Astyanax species to access the importance of habitat differentiations as spatial complexity in two tropical reservoirs with different environmental features. The NMDS analysis indicated separation in the diet of these species between reservoirs (Stress= 8.28%). Additionally, analysis of variance revealed a significative difference in the volume of food itens ingested between the reservoirs (Anova one-way F(1, 132)=4.4446; p= 0.037...
Acta Limnologica Brasiliensia
Aim The diet of Plagioscion squamosissimus present in the Santa Cruz Reservoir, Rio Grande do Norte, Brazil, was investigated, evaluating the influences of spatial and temporal variations and abiotic factors in the utilization of food resources. Methods The samplings were performed quarterly between February 2011 and November 2014. Of the 525 specimens captured, 375 presented food items in the stomachs. The diet was determined using: (i) Feeding Index (IAi); (ii) and the graphical interpretation of the food strategy through non-metric multidimensional scaling (NMDS) analyzes, the differences in diet being tested from Permutational Multivariate Analyzes of Variance (PERMANOVA). To verify if environmental variables influence the Canonical Correspondence Analyzes (CCA) were used, using the data from the IAi the environmental data, being the significance of the axes tested through Monte Carlo simulations. Results The species feed mainly on items of animal origin, vegetable being a resou...
Journal of Animal Behaviour and Biometeorology
The knowledge of the fish trophic structure has been outstanding for providing relevant information on the functioning of the ecosystem in which they are inserted, mainly in dammed environments of semiarid regions that suffer constant changes in the level of water, resulting in alterations, especially in the feeding of the fish due to the variation of the food resources throughout the year, causing changes in the diet of the local ichthyofauna. Within this context, the objective was to describe the trophic categories of fish species in freshwater environments of the Rio Grande do Norte state. Seven trophic guilds were recorded: Detritivore/iliophagous, Insectivorous, Carcinophagous, Piscivorous, Herbivorous and Omnivorous. Through the results, it is observed that the fish species inserted in different environments of the state present the same food pattern, demonstrating flexibility on the diet, prevailing a generalist alimentary habit.