Abstract
Aiming to study the changes in the diet of Astyanax altiparanae in the early developmental stages, in the presence of Eichhornia crassipes (EC) and Lemna sp. (LM), larvae of Astyanax altiparanae were stocked in eight tanks of 900 L (500 ind. tank -1 ), four with EC and four with LM covering 50% surface. Tanks were inoculated with plankton and received 3.0 g inorganic fertilizer (NPK-7:14:8) and 1.5 g every week. At every three days, three larvae were taken from each tank, fixed in 4% formaldehyde and grouped into four age classes (I: 6 to 12 days, II:15 to 21 days, III:24 to 30 days; IV:33 to 39 days). The analysis of dominance and frequency of occurrence (FO) of food items indicated that, at this stage, A. altiparanae is generalist. In class I, there was a greater dominance and FO of Lecane bulla and Alona sp. in digestive tracts in the presence of both EC and LM, respectively; and larvae started to consume larger organisms, such as Chironomidae, in other age classes with EC. In the presence of LM, Alona sp. was dominant in class II; Chironomidae, in class III and Centropyxis sp., in class IV. Diatoms have greater FO both in EC and in LM. In class III, with EC, Chironomidae had higher FO, as well as Arcella sp. and Scenedesmus spp. with LM. The highest FO in class IV was found for L. bulla and Scenedesmus spp., with EC and LM, respectively. It can be concluded that EC and LM influenced the diet of Astyanax altiparanae , with alterations according to the availability of organisms and increase in age.
Highlights
Fish hatchery, which sustains the large scale production of quality fingerlings, has faced many problems with frequent failures, and the food factor is the most important (Cestarolli, Portella, & Rojas, 1997; Gerking, 1994).The early stage of most fish is a period of rapid morpho-anatomical changes and during this lifeActa Scientiarum
The percentage values of dominance and frequency of occurrence in the contents of the digestive tracts of Astyanax altiparanae, when represented by the Graphic Method of Amundsen, et al (1996) modified from Costello (1990), clearly indicate that this fish, at the early stages of development, in different age classes, in tanks with Eichhornia crassipes and Lemna sp., shows tendency to the generalist feeding strategy (Figure 1). This is because there were higher values of frequency of occurrence and low values of dominance for various food items
Our findings indicate that Astyanax altiparanae shows a generalist feeding strategy (Figure 1), which corroborates data found in the literature for different environments
Summary
Fish hatchery, which sustains the large scale production of quality fingerlings, has faced many problems with frequent failures, and the food factor is the most important (Cestarolli, Portella, & Rojas, 1997; Gerking, 1994).The early stage of most fish is a period of rapid morpho-anatomical changes and during this lifeActa Scientiarum. The early stage of most fish is a period of rapid morpho-anatomical changes and during this life. The shift from endogenous to exogenous feeding is a major difficulty faced in farming juveniles of rheophilic species (Gerking, 1994), as well as cannibalism that occurs in the first days of larval life (Feiden, Hayashi, & Boscolo, 2006). Studies on the diet during the early stages of fish development are of great importance to understand its role in the community, an opportunity to know one of the most critical steps for fish hatchery, which can help in the development of fish farming (Makrakis et al, 2005; Qu et al, 2012) and in determining priority areas for the maintenance of natural stocks
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