Spawning movements of winter flounder in the southern gulf of Maine

To study the spawning movements and habitat use of adult winter flounder in the southern Gulf of Maine, pre-spawning adults were acoustically tagged offshore and tracked in 2009. In addition, tows were made in the offshore study area to quantify how their reproductive status changed over time. Peak spawning of winter flounder in Ipswich Bay occurred in late April to early May. Only six fish (15%) were detected entering estuaries between April and August indicating that the majority of the tagged fish did not spawn in estuaries but remained in deeper, coastal waters. Most horizontal movements (migration) occurred at night. Vertical ascents off-bottom were associated with both nocturnal periods and horizontal migrations. Flounder often rose significantly in the water column (as much as 45 m above the sea floor) during nocturnal migratory movements; it is likely that these migrations were facilitated by selective tidal transport. Conventional tagging returns (336 fish tagged, 4% return rate) show both long and short movements. Fish have been recaptured from 2 to 57 km from their tagging sites in depths of 6 to 75 m.  Days at liberty range from 33 to 230 days, with an average of 109 days.