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



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n Female 

  Male 



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n i M il' ir i i n r P l' 



PP rr rPP 



gi CM (o 



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*- lo en CO 



Date 



Figure 4 



Total number of feeding bouts observed in the research aquarium shown on a daily basis for female and 

 male winter flounder ND = no data available. 



Most female winter flounder demonstrated growth 

 in total length ( mean= 1.0 cm, SD= 1.0) during the three- 

 month experimental period, despite the cold tempera- 

 ture and high spawning activity. Change in length of 

 males (mean=0.1 cm, SD=0.6) was less but the gender 

 difference was not significant ( Student's ^=-1.91, df=7, 

 P<0.098) because of large individual variation. 



Locomotory pattern General activity in winter 

 flounder during the spawning season began near 

 sunset and remained high throughout the night until 

 sunrise (Fig. 7, A and C). After spawning ended, ap- 

 proximately equal levels of activity were observed dur- 

 ing day and night, with highest levels during afternoon 

 and evening hours. Diurnal patterns of locomotion were 

 somewhat different in males and females. During the 

 spawning season, male fish began moving somewhat 

 earlier in the evening than females, and the general 

 level of activity was higher Postspawning, female fish 

 shifted more strongly to an afternoon activity pattern 

 whereas males continued a high level of activity into 

 Jthe night and early morning hours (Fig. 7). 



Swimming speeds of winter flounder were gener- 

 ally near 20-25 cm/sec, and there was no apparent 



effect of date or time of day during active hours. How- 

 ever, male fish were significantly faster (overall 

 mean=26.1 cm/sec, SD=6.6l than females (mean=21.2 

 cm/sec. SD=4.6; Student's ^=14.61, P<0.001). 



Field observations 



Physical conditions Temperature in the Navesink 

 River estuary ranged from 2.2°C in mid-February to 

 ll'C at the end of the field study in late April, and 

 there was relatively little temperature variation 

 among the eight field stations ( Fig. 8A). Salinity near 

 station 6 in the eastern part of the study area ranged 

 from 15 to 23 ppt over the study period. At station 1 

 in the western part of the study area, salinity was 

 10-21 ppt, except for a brief period of low salinity 

 (7-10 ppt) on 1 April 1997.Therefore, the entire sam- 

 pling area was polyhaline, and there was a slightly 

 wider range of salinity in the west than in the east. 

 Dissolved oxygen was always high (>8 mg/L) at the two 

 sites where measurements were made continuously. 



Population structure, reproduction, and migration 



Numbers of winter flounder in the Navesink River 



