El pez Trachelyopterus striatulus (Siluriformes: Auchenipteridae) como herramienta de muestreo de la entomofauna en un embalse tropical

Abstract

The fish Trachelyopterus striatulus (Siluriforms: Auchenipteridae) used to sample insects in a tropical reservoir. The study of aquatic environments is sometimes difficult to do with normal sampling methods that use gears. Insectivorous fishes represent good users of these ecosystems and analyzing the aquatic organisms present in fish stomachs, is an alternative way to determine resource abundance and utilization. In this paper, the potential of Trachelyopterus striatulus as an insect sampler was examined through dietary analyses of 383 individuals caught between April 1999 and March 2000 in Lajes Reservoir, a 30 km 2 oligotrophic impoundment in Southeast Brazil. We estimated frequency of occurrence and Schoener's index of similarity. Diet changes among seasons and reservoir zones were addressed with DCA and ANOVA analyses. Its diet was 92.1% insects (ten orders and nine families). Hymenoptera (57.90%), Odonata (39.76%), Trichoptera (27.41%), Ephemeroptera (26.25%) and Coleoptera (28.96%) were the most common groups. Highest insect occurrence and richness were recorded in autumn-summer, a period of greater rainfall and insect activity. Formicidae, the dominant prey item in all seasons, appeared to be especially important in spring, a season marked by shortness of food resources. Trichoptera and Ephemeroptera were the most consumed prey items in the other seasons. Highest insect occurrence and richness were recorded in the middle and upper reservoir zones, respectively. Trichoptera and Ephemeroptera prevailed in the upper zone, where small pristine rivers and tributaries are abundant, whereas Formicidae and Belostomatidae predominated in the lower and middle zones. Because of its abundance in many freshwater ecosystems of Brazil, the ubiquity of insects in its digestive tract and the low level of prey degradation, T. striatulus has potential as an insect sampler of Neotropical reservoirs. However, conventional sampling in Lajes Reservoir is necessary to compare the effectiveness of T. striatulus with other insect sampling methods.

Use of trophic ecology of omnivorous fish and abiotic factors as supporting tools for assessing environmental impacts in a neotropical river

“…T. striatulus is also considered omnivorous, encompassing zoobenthos, microcrustaceans, and plants (Silveira et al, 2013). The food preference found for the species in the present study is supported by the findings of Dias et al (2005) and dos Santos et al (2009), who identified insectivorous habits in lotic systems in the southeast region. The presence of a higher percentage of terrestrial—and even some aquatic—insects may be related to the smaller size of the mouth opening, suggesting an adaptation to ingest smaller foods (dos Santos et al, 2015).…”

“…Furthermore, R. quelen has been used as an evaluation tool in various environmental assessments, providing insights into water contaminants (Becker et al, 2009; Ghisi et al, 2011; Marins et al, 2021; Severo et al, 2023). T. striatulus has served as a biodiversity bioindicator for insects and is also associated with the types of exogenous food in water (dos Santos et al, 2009). On the contrary, C. gariepinus is an exotic fish, dominant in many rivers in Africa, and can occupy various trophic levels (Khan et al, 2021; Low et al, 2022).…”

Ficha de Trachelyopterus striatulus

“…No Brasil, Trachelyopterus striatulus ocorre nos rios costeiros, com registros desde o estado da Bahia até o estado de São Paulo (Ferraris Jr., 2003;Montag et al, 2004;Santos et al, 2009;Mesquita et al, 2011;B. Calegari, com.…”