Stoner et al : Behavior of Pseudopleuronectes americanus during spawning, feeding, and locomotion 



1013 



Spawning, migration, and habitat use 



Previous studies have shown that 

 winter flounder in the mid-Atlantic 

 region migrate to shallow inshore 

 waters to spawn during the late win- 

 ter (Perlmutter, 1947; Poole, 1966; 

 Scarlett and Allen, 1992), and it is 

 known that the Navesink-Shrews- 

 bury River estuarine system is an 

 important spawning ground ( Phelan, 

 1992; ScarlettM. Phelan's study and 

 our investigation provide direct evi- 

 dence that winter flounder immi- 

 grate to the Navesink estuary be- 

 tween early February and March. 

 Flounder abundance was lowest 

 when water temperature was lowest 

 (2.2'^C in mid-February) and in- 

 creased rapidly with subsequent tem- 

 perature rise. In fact, high and rela- 

 tively constant catches of winter 

 flounder occurred in the Navesink 

 estuary at temperatures of 6-ll°C. 

 This is consistent with earlier obser- 

 vations that adult winter flounder 

 emigrated from bays in southern 

 New Jersey when water temperature 

 declined below 3.5"C and returned 

 when temperature rose to 6°C (Danila, 

 1978). Most adult males and females 

 had ripe gonads upon entry to the 

 system in late winter, and most were 

 spent by the end of April. This pat- 

 tern of seasonality is consistent with 

 previous findings (Pearcy, 1962; 

 Scarlett and Allen, 1992). 



It is likely that the most important 

 spawning area for winter flounder in 

 the Navesink River was in the middle 

 reach. Reproductively ripe male win- 

 ter flounder were found throughout 

 the estuary; however, highest num- 

 bers of ripe females were found west 

 of station 5, and only one nearly spent female was 

 collected farther down the estuary. Scarlett and Allen 

 ( 1992 ) found that the middle reach of the Manasquan 

 River estuary. New Jersey, was a major spawning 

 ground for winter flounder, as were the upper reaches 

 of the Mystic River estuary, Connecticut (Pearcy, 

 1962 ), and Narragansett Bay, Rhode Island ( Powell- ). 



kW?-Ampefisca sp 



CRU=Crustacea 



HYD=Hydrozoa 



MAC=/Macoma sp 



MIS=Miscellaneous 



MOL=Mollusca 



MYS=Mysiclacea 



MYA= Uya arenana 



POL=Polychaeta 



Figure 13 



Composition of diet by percentage volume in winter flounder collected at eight 

 stations along the length of the Navesink River estuary during winter and 

 spring 1997. 



- Powell, J. C. 1989. Winter flounder tagging study. 1986- 

 ^ 1988, with comments on movements. Rhode Island Division 

 of Fish, Wildlife, and Estuarine Research. P.O. Box 218, West 

 Kingston, Rhode Island 02892. Unpubl. report. 



Several different physical and chemical factors 

 could affect the location of spawning habitats. Tem- 

 perature may have influenced the seasonal migra- 

 tion to the Navesink estuary; however, there was little 

 variation in temperature along the axis of the estuary, 

 and other factors probably influenced exact spawning 

 location. McCracken (1963) found that adult winter 

 flounder died in 8 ppt salinity; therefore, upstream 

 migration is probably limited by this variable. Neither 

 males nor females were abundant in locations where 

 salinity was frequently near or below 10 ppt. 



