Biología alimentaria y reproductiva de <i>Farlowella vittata</i> (Siluriformes: Loricariidae) en la cuenca del río Güejar, Orinoquía, Colombia

Abstract

Neotropical fish live in streams with considerable spatial and temporal variability of their food items. Food availability depends on different factors such as discharge, channel morphology, physicochemical conditions and interactions with other species, as well as their food habits. On the other side, good food availability results in reproductive success. Because the study of those changes contributes to a better understanding of trophic interactions in fish populations, the present work describes and evaluates aspects of diet and reproduction of Farlowella vittata in Pringamosal Creek, Güejar River drainage, Orinoco River basin, Colombia. Five collecting expeditions were done during both high and low rain seasons of 2008 and 2009. Physical and chemical water parameters were measured, and fish were captured from several points along the total length of the 7km stream, to characterize their biometry and stomach contents. Our results showed that Pringamosal creek is a first order stream, about 3.5m wide and with an average depth of 1m in our study area. Dissolved oxygen values were 6.2mg/L during low water and 2.7mg/L during high water phase. The creek is classified as oligotrophic but with a tendency to eutrophication. A total of 130 fish samples were analyzed. Fishes were assigned to seven size range categories between 86.0 and 175.5mm standard length (SL). Stomach contents revealed that the diet of this species consisted mainly of algae (Bacillariophyceae) (84.6% Abundance Relative), but we observed a variation in the diet according to season; during low rainfall it feeds on phytoplankton (86.47% A.R.) and during high rainfall on zooplankton as well as plant material and organic material (0.685% A.R. and 18.83% A.R., respectively). A Kruskal-Wallis ANOVA showed statistically significant differences in food items between sexes. The condition factor (K) indicated that the species was well fed. Size at sexual maturity was 154mm SL for males and 124mm SL for females. The gonadosomatic index (RGS) showed that this fish reproduced during high water (April-May) season, and females showed a fecundity of 1 819 ovocites, with an average diameter of 1.4mm. Although parental care was not observed during this study, it is well known that males protect their eggs and juveniles, making them easy to capture during the breeding periods identified in this study, and at the same time, vulnerable to overexploitation. We recommend an urgent management plan for the conservation of this species, since at this time, no fishing controls are enforced even though it is harvested as an ornamental species.