Fish thieves: An alternative tactic of food capture in a Neotropical frugivorous species (Brycon falcatus)

Abstract

AbstractFrugivorous fishes switch their diets seasonally in response to fluctuating food availability; a strategy that maximizes energy and nutrient intake and reduces competition for food. Kleptoparasitism is a form of competition that involves the stealing of already‐procured items, for which the host has invested energy in prey capture. We did not find previous studies on kleptoparasitism among Neotropical fish. Here we contribute the first record of kleptoparasitism among a frugivorous fish species. The matrinxã (Brycon falcatus) is a member of an iconic genus of broadly distributed frugivorous fishes. We made focal daylight underwater observations (by snorkeling) of frugivorous fish behavior in an Amazonian stream. Opportunistic feeding interactions between a school of juvenile matrinxã, (B. falcatus) and an individual of threespot leporinus (Leporinus friderici) were observed. The matrinxã stole the fruit that was captured in the substrate by the leporinus. Brycon falcatus usually lives between the middle of the water column to the surface of rivers and streams while Leporinus friderici occupies the lower portion of the water column and it actively forages close to the substrate. This suggests that stealing food from a benthic feeder is an opportunistic ecological interaction to take advantage of scarce resources during the period of food scarcity. This alternative technique of capturing fruits may be advantageous (i.e., save energy expenditures related to searching) for young matrinxã who do not eat fruit as frequently as adults. Our results reflect the trophic plasticity and foraging opportunism characteristic of most tropical freshwater fish. We believe that the hydrological period in which the observations were made, when a few trees were bearing fruit, can favor fruit stealing by Brycon falcatus.