Stoner et al.: Behavior of Pseudop/euronectes americanus during spawning, feeding, and locomotion 



1007 



1H A 



12 



10 H 



6 i 

 4 

 2 

 



Spawning period 



Female 



111 



I I 



2 



-1 — T — I — I — I — I — I — I — I — I — r" 

 6 8 10 12 14 16 18 20 22 



14- C 



12 - 

 10 



8 



6 H 



4 



2 







Male 



I I I I I I I 



2 4 6 





T — I — 1 — I — I — r — I — I — 1 — r 



8 10 12 14 16 18 20 22 



14 

 12 

 10 



8 



6- 



4- 



2 







B 



Postspawning period 



Female 



6 8 10 12 14 16 18 20 22 



16 18 20 22 



Figure 6 



Hourly frequency of feeding during spawning and postspawning periods for (A, B) female and {C, D) male 

 winter flounder in the research aquarium. Values represent mean numbers of observed events per hour ±1 

 standard error The dashed vertical lines show the times of artificial sunrise and sunset in the aquarium at the 

 midpoint of the spawning season. Photoperiod was maintained on a natural cycle for the latitude of the laboratory. 



tively ripe, as were 40% of males between 10 and 15 

 cm. A steady decline in male GSI began in March (Fig. 

 9B), but ripe males (mean GSI=7.3, SD=4.4) were col- 

 lected later than ripe females, through 11 April. 



Although the number offish collected at any one 

 station was not large, the Station x Gender interac- 

 tion in the ANOVA indicated that male and female 

 flounder had different distributional patterns in the 

 estuary (Table 1). Males were more abundant than 

 females at stations in the lower estuary (stations 7 

 and 8), whereas females were more abundant in the 

 middle and upper reaches (stations 1-6) (Fig. 10). 

 These gender-specific distribution patterns were gen- 

 erally consistent, as indicated by the nonsignificant 

 Date X Station x Gender interaction term in the 

 ANOVA (Table 1). Ripe males were collected through- 

 out the estuary in proportions ranging from 14% of 

 individuals at station 6, to 100% at stations 1 and 2. 

 In contrast, all ripe females were collected at sta- 

 tions 1-4, with the exception of one partially spent 

 female collected at station 7. 



The length distribution of female winter flounder 

 at most of the sampling stations showed two modes 

 (Fig. 11). Large females (mean length=29.7 cm, 

 SD=0.6) were collected at all eight stations but were 

 most abundant in the middle reach (stations 3-6). 

 Small females (<20 cm TL), all of which were repro- 

 ductively immature, were most abundant in the up- 

 per estuary, with approximately equal numbers of 

 small fish at stations 1-4. Size groups were less ob- 

 vious in male winter flounder ( Fig. 11), but it is clear 

 that the mean size of male fish was larger at sta- 

 tions in the lower river (stations 5-8) than in the 

 upper river, and small fish were most abundant at 

 stations 1-3. From 28 March through the end of the 

 sampling period, large numbers of flounders were 

 collected only at station 6. Virtually all the fish in 

 the lower river during this late part of the collecting 

 season were spent. 



Feeding Stomach fullness in winter flounder var- 

 ied with date, gender, and age (Fig. 12). Highest full- 



