New insights into the trophic ecology of the recently described top predator fish Hoplias argentinensis

Hoplias argentinensis is a recently described species in the extreme south of the Neotropicalregion. Despite its wide distribution, high trophic level, and relevance for sport fishing, detailedinformation about its diet is lacking. In this work, new insights on the trophic ecology ofH. argentinensis from two Pampa shallow lakes in Argentina are presented. For this purpose,complementary characteristics of its diet were explored, particularly aspects of selectivity, feedingstrategy, trophic breadth, and individual specialization, as well as feeding patterns associatedwith size and sex. The guts of adult specimens from La Margarita (34°38’S, 63°44’W) and KakelHuincul (36°48’S, 57°47’W) were studied. Bryconamericus iheringii and Odontesthes bonariensiswere the most consumed items. Shrimp was abundant in a few specialized individuals. There wasa tendency for prey size to increase with predator size, and there were no differences betweensexes. Both populations presented a zoophagous and mainly an ichthyophagous condition, witha relationship between the most frequently ingested food item and its abundance in theenvironment, indicating a random behavior when selecting preys. This work presents the firstcontribution to the knowledge of the diet of a species belonging to the H. malabaricus complexusing complementary information from two populations.