Killer whales (Orcinus orca) in Norwegian waters have long been known to rely on 28 Atlantic herring (Clupea harengus) as a main prey resource. However, research almost 29 exclusively conducted at seasonal herring grounds may have biased studies away from 30 detecting other potentially significant prey species. Since 2013, dedicated research efforts 31 have focused on monitoring killer whale occurrence and foraging ecology throughout the year 32 in northern Norway. This study presents results on site-fidelity of photographically identified 33 individuals, predation records and behavioral patterns from five spring seasons (March-April) 34 in 2014-2018 in Andfjord, northern Norway. A minimum number of 75 adult and subadult 35 killer whales (out of a catalogue of 971 individuals) returned seasonally to the study area for 36 foraging and residency for up to six weeks. Lumpfish (or lumpsucker, Cyclopterus lumpus) 37 was the only type of prey identified (based on molecular or visual identification) on 22 38 predation events from 2016 (n=4), 2017 (n=2) and 2018 (n=16). Spatial group cohesion 39 observed when foraging was a potential adaptation for efficiently hunting this prey species. 40 These whales were also encountered at herring wintering grounds the same years, but with 41 different group sizes. Such behavioral adaptations suggested intra-annual switching between 42 prey resources and foraging strategies. 43