Preliminary observations of hunting behaviour by a freshwater threatened Leuciscidae

Abstract

Freshwater ecosystems host diverse fish species that employ various foraging strategies, including hunting, a behaviour more commonly documented in marine environments. This study focuses on the threatened Iberian chub, Squalius pyrenaicus, in the Vascão River, Portugal, a species known for its opportunistic feeding. Using an underwater camera, we observed 45 predatory events in which S. pyrenaicus employed two tactics: solitary pursuit and group hunting. In group hunting, individuals coordinated attacks, encircling and taking turns pursuing prey. While all attacks seem unsuccessful, one feeding event was recorded where two S. pyrenaicus individuals interacted to capture a prey fish. Our findings suggest that S. pyrenaicus may rely on rudimentary social behaviors during solitary and group hunting, potentially influenced by environmental factors. This is the first report of such behaviour in this species, underscoring the need for further research into social and cognitive aspects of freshwater fish predation, particularly in light of ecosystem threats like invasive species and climate change.