Diet of characin,Brycon falcatus(Muller and Troschel, 1844) in the Amazon Basin: a case study on an attractant for fish in the Teles Pires River

Abstract

Summary The use of fresh soybeans as an attractant in fishing has been altering the diet of the characiform Brycon falcatus, which are thriving at fishing spots. This has subsequently affected the amount of abdominal fat in the species from the Tapajós River basin, Southern Amazon. In the Teles Pires River basin region, one of the most common capture techniques employed by fishermen is the use of attractant feeds (soybeans, corn, cassava) at certain locations to attract mostly omnivorous fish. Tourists also feed fish chips and breadcrumbs. In the experimental design, rivers were mapped according to attractant availability to develop an attractant‐density classification system comprising four rivers with different attractant densities (low, medium, and high), plus a river serving as control (no attractants). Monthly collections were carried out during the 2012 and 2013 dry seasons. For diet analyses, methods of frequency of occurrence and relative volume were used to calculate the feeding index (IAi) of 97 specimens. For analyses of abdominal fat, an index was calculated by dividing the wet weight of the abdominal fat by the total wet weight of each individual. Standard length ranged from 15.0 to 48.5 cm, and weight between 0.18 and 4.40 kg. Composition and diversity of diet items changed with the increasing density of attractants. In the river with a high attractant density, fresh soybeans and corn were dominant diet items; in the control river, the diet was natural (e.g. seeds, fruits, leaves, and insects) and therefore similar to those described for B. falcatus in undisturbed environments. Fish collected from rivers with high attractant densities were in better condition than those from the river with no attractants. Although use of attractants is prohibited by State legislation, there are no inspections. This study clearly shows an alteration in the natural diet and abdominal fat of B. falcatus resulting from an imbalanced, high‐calorie feed via an attractant. It is recommended that these areas be monitored for the preservation of B. falcatus.

Assessment of mercury contamination in Brycon falcatus (Characiformes: Bryconidae) and human health risk by consumption of this fish from the Teles Pires River, Southern Amazonia

“…Brycon falcatus has omnivorous food habit with a tendency to frugivory (Correa et al, 2007). In the Teles Pires river basin, due to the great supply of in natura soybeans in attractants, the B. falcatus diet is mainly based on soybeans (Matos et al, 2016a). Thus, the low levels of THg in B. falcatus observed in the present study is probably due to its food habit.…”

Length-weight relationship and condition factor of the Characidae matrinxã,Brycon falcatus(Müller & Troschel, 1844), in the Teles Pires River, southern Amazon

“…Matos et al. () found that specimens of Brycon falcatus captured in regions where attractants were used showed a diet composed of 83% soybean, while the diet of fish caught in locations where there were no attractants was composed of fruits, seeds, fish, crustaceans, flowers, leaves and insects. Brycon falcatus (Müller and Troschel, ) is an omnivorous (Albrecht, Caramaschi, & Horn, ) and migratory species commonly known as matrinxã, and belongs to the Bryconinae subfamily.…”

“…In the basins of the Amazon River systems of the Brazilian mid-west, one technique commonly used by fishermen to capture fish, particularly omnivorous species, is the use of food attractants. This practice is known regionally as "cevas" (attractive to fish) (Matos, Silva, Andrade, & Carvalho, 2016). The attractants are offered in situ as large quantities of soybean (Glycine max) and provided continuously (Matos & Carvalho, 2015;Matos et al, 2016), which may adversely affect fish behaviour and physiology (Francis, Makkar, & Becker, 2001).…”

“…This practice is known regionally as "cevas" (attractive to fish) (Matos, Silva, Andrade, & Carvalho, 2016). The attractants are offered in situ as large quantities of soybean (Glycine max) and provided continuously (Matos & Carvalho, 2015;Matos et al, 2016), which may adversely affect fish behaviour and physiology (Francis, Makkar, & Becker, 2001). Matos et al (2016) found that specimens of Brycon falcatus captured in regions where attractants were used showed a diet composed of 83% soybean, while the diet of fish caught in locations where there were no attractants was composed of fruits, seeds, fish, crustaceans, flowers, leaves and insects.…”

“…The attractants are offered in situ as large quantities of soybean (Glycine max) and provided continuously (Matos & Carvalho, 2015;Matos et al, 2016), which may adversely affect fish behaviour and physiology (Francis, Makkar, & Becker, 2001). Matos et al (2016) found that specimens of Brycon falcatus captured in regions where attractants were used showed a diet composed of 83% soybean, while the diet of fish caught in locations where there were no attractants was composed of fruits, seeds, fish, crustaceans, flowers, leaves and insects. Brycon falcatus (Müller and Troschel, 1844) is an omnivorous (Albrecht, Caramaschi, & Horn, 2009) and migratory species commonly known as matrinxã, and belongs to the Bryconinae subfamily.…”