Homing ability of displaced stream-dwelling green sunfish

The ability of individually tagged green sunfish (Lepomis cyanellus) to home after displacement either upstream or downstream was studied in a small central Ohio stream in the late spring and early summer, and their movements were compared to those of non-displaced control fish. The majority of control fish were sedentary; 56% of recaptures were either in the same 20-m. section of stream in which the fish were initially captured or in one of the adjacent 20-m sections. Some control fish moved greater distances; 15% moved >= 400 in between captures but only 3.5% moved >= 1,000 in. Fish displaced 400 m or 1,000 in showed an opposite pattern of movement; 53% were initially recaptured >= 400 in from the site of release and only 18% stayed in the 20-m section where they were released or in an adjacent 20-m section. The most common initial movement (45%) was homing (i.e., returning to their original site of capture); the second most common (31%) was moving homeward but all the way. Only 6% of displaced fish initially moved in the wrong direction. Homing tended to be rapid; some fish homed within three days from both distances and directions of displacement. Overall, fish homed better from 400 in (62%) than from 1,000 in (23%). This ability to home following displacements of these lengths was not necessarily expected in a species reported to have a small home range.