Winter predatory efficiency and periodicity of the non-native brown bullhead Ameiurus nebulosus.

Winter is a challenge for fish in temperate regions as it is likely to create a bottleneck for small-bodied fish due to starvation. Resource consumption could contribute substantially to the overwinter survival of fish. Nevertheless, fish feeding activity and related impacts at low temperatures are understudied. We assessed the hunting periodicity and functional response of a non-native European brown bullhead Ameiurus nebulosus population under winter conditions. Our results provide evidence of predation at temperatures as low as 3 °C, while the hunting periodicity was clearly identified as nocturnal. Furthermore, a visible decrease in handling time was observed at 3 °C compared to 4.5 °C, suggesting that this temperature could be a thermal threshold in A. nebulosus' ecophysiology. Moreover, the potential predation impact calculated from the functional responses revealed a severe increase in resource consumption from 3 °C to 4.5 °C, suggesting that such slight temperature increase could accentuate A. nebulosus predation impact. Ultimately, our results suggest that such winter predation activity could harm other species' recruitment and play an important role in the establishment success of A. nebulosus non-native populations.