Feeding ecology of the leaf fish Monocirrhus polyacanthus (Perciformes: Polycentridae) in a terrafirme stream in the Brazilian Amazon

Monocirrhus polyacanthus (Polycentridae) is a remarkable leaf-mimicking fish that inhabits streams, lake and river margins along the Amazon basin. Despite its obvious predatory habits and being frequently present in the international aquarium trade, little is known about its diet under natural conditions. We examined 35 specimens of leaf fish (28.5-82.0 mm SL), of which 19 had food the stomach. Thirty-three preys were found in the stomach contents, 19 of which were measured (2.0-33.0 mm total length). Up to five preys were found in the stomach contents of a single leaf fish specimen. The diet of the leaf fish was constituted by fish (63.15% FO, n = 12) and invertebrates (36.3% FO, n = 4); fish and invertebrate preys occurred together in three stomachs (15.8% FO). Of the 33 prey found in the stomachs, 21 were fish and 12 invertebrates. Among the consumed prey fishes, Characiformes and Perciformes represented 76.1% and 14.2% respectively. Characidae was the most commonly recorded prey family, followed by Lebiasinidae. Invertebrates were represented by shrimps (Decapoda) and insects (Coleoptera, Hymenoptera, Ephemeroptera and Odonata). There was a positive relation between the size of the leaf fish specimens and of its consumed preys. The combination of leaf fish's visually effective body camouflage and the reduced activity of the characids at crepuscular hours probably allow the capture of such fast moving preys. The coiled position of the fishes found in the stomach of M. polyacanthus possibly allowed the accommodation of more than one prey simultaneously, which seems to be important for predators that consume proportionally large preys that are captured only occasionally. © 2010 Sociedade Brasileira de Ictiologia

Amazon commercial fishing dynamics: a space macroscale analysis on fishing variables/ A dinâmica da pesca comercial amazônica: uma análise em macroescala espacial sobre variáveis da pesca

The landscape and the dynamics of seasonal flooding should be considered in the development of fishery management measures in the Amazon, as these factors determine the distribution and ecology of fishery resources and consequently the behavior of fisherman and fishery. In this context, the spatial dynamics of commercial fishing in the upper and lower reaches of the Solimões River were analyzed and the hypothesis that fishing is homogeneously developed by the Amazonian landscape was discussed. Catch data, number of fishers per trip, duration of fisheries and fishing locations were collected in 2012 at the main landing centers of the municipalities of Benjamin Constant and Iranduba. The geographical coordinates of fishing locations were recorded in 2018 using a hydrographic map of municipalities, a list of fishing locations documented in 2012 and the help of fishermen. The spatialization of fishery information was performed by municipality, by fishing location and by river regime period using the QGIS software (2.18). Thirty-two fishing sites were identified in the municipalities. The fishermen operated within a 175 km radius of Benjamin Constant during both periods of the river regime. In Iranduba the area of operation was 28 km in high water and 35 km in low water. In Benjamin Constant the Solimões River recorded the highest catches in both periods. In Iranduba the Iranduba coast and Manaquiri beach recorded the highest catches during periods of high and low waters, respectively. In Benjamin Constant the highest yields were recorded in the 35 km zone far from the municipal headquarters in both periods. While in Iranduba, in the high water period the highest yield was recorded in locations closer to the municipal headquarters than in the low water period. With the analysis of the spatial dynamics of commercial fishing we reject the hypothesis that fishing is homogeneously distributed throughout the Amazonian landscape and we propose to consider the spatial aspects of this activity in management systems