Experimental protocol
The experiment started on the day following capture and was repeated on three consecutive days for all fish (trial 1-3). Each fish was removed from its home tank using a small hand-net and transferred the short distance (~1.5m) to the experimental tank where it was placed in a release compartment at one end of the tank. The release compartment was 30x40cm and darkened using black plastic on all sides and top covering. As soon as the fish was in the release compartment an opaque plexiglass divider was lifted by 5cm allowing the fish access to the main arena. The main arena was 60x40cm with all sides covered with blue and green aquarium background (plant patterned) preventing the experimental fish from seeing outside the tank. The main arena was visually divided in three equal areas by black lines on the bottom of the tank. Four food patches were placed within the arena each with two bloodworms taped to a small glass petri dish. Two of the patches were sheltered by a round of four small stones and two were unsheltered. The food patches were in areas two and three while the first area, closest to the release compartment, was empty (Fig. 1). The water level in the experimental tank was 10cm with continuous flow of aerated and chilled (12.0°C) water. The behavior of fish in the experimental tank was videoed from above for 10-min. From the 10-min videos recorded we extracted (1) latency to explore, i.e. the fish fully moved out of the release tank; (2) latency to forage, the time to locate and attempt to feed at any of the food patches and (3) activity, the number of times a fish fully crossed between the three areas in the tank. It was also noted if feeding took place at an open or sheltered food patch.