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



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Figure 2 



(A) Number of winter flounder spawnings obsei-v-ed on a daily basis in the research aquarium. (B) Lan'al 

 abundance in the research aquarium as a function of date. The index represents only newly hatched larvae 

 because older larvae were extracted by aquarium filtration. 



in the system, we estimated that each male (on av- 

 erage) spawned approximately 147 times during the 

 season. 



Larval abundance The first winter flounder larvae 

 were observed in the aquarium on 19 February, 11 

 days after the first spawning was observed. A week 

 of low larval abundance occurred in March, but lar- 

 vae were constantly present until 5 April (Fig. 2B). 

 Because there was no appreciable food for fish lar- 

 vae in the aquarium, most of the larvae observed 

 were at yolksac and early stages. 



Courtship behavior The spawning season was char- 

 acterized by a high frequency of following behavior 

 (Fig. 5A). Only a small amount of following was ob- 

 served in the days before and after the spawning 

 season, but 50-200 following events were observed 

 each night between 8 February and 8 April, decreas- 

 ing steadily after mid-March. This pattern reflected 

 ^spawning frequency (Fig. 2A), and there was a weak 

 but positive correlation (r=0.531, P<0.001) between 

 the two forms of behavior. 



Avoidance events were approximately one order of 

 magnitude less frequent than following events (Fig. 

 5), but the seasonal patterns were similar, and there 

 was a positive correlation between these behaviors 

 (r=0.786, P<0.001). The correlation between avoid- 

 ance and spawning was also positive (r=0.441, 

 P<0.001). Most courtship behavior occurred after 

 sunset between 1700 and 0400 h, with a broad mode 

 around 2100 h (Fig. 3, B and C). Very few interac- 

 tions occurred in daylight. 



Feeding and growth The seasonal pattern of feed- 

 ing was entirely different from the patterns of spawn- 

 ing, following, and avoidance behaviors. First feed- 

 ing occurred on 10 February, then increased slowly 

 over time — some apparent oscillations, however, were 

 embedded in the overall trend (Fig. 4). For example, 

 an approximately 10-day periodicity occurred be- 

 tween 12 February and 20 March; this was indepen- 

 dent of the dates when fresh food was added. All feed- 

 ers that could be identified prior to 18 March were 

 female. Females were responsible for 90% of all feed- 

 ing events recorded (n=3673), and this percentage 



