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



1001 



regardless of feeding duration, 

 when a fish entered the food 

 distribution area and made 

 obvious feeding motions to- 

 ward the clam pieces. Analysis 

 of video tape from the two cam- 

 eras for four dates during 

 midspawning season revealed 

 that there were no significant 

 differences in daily counts of 

 spawning, courtship, and feed- 

 ing as recorded by the two cam- 

 eras (paired-sample t tests, 

 P>0.30); therefore, the second 

 camera was used only as a 

 backup for recorder failure (e.g. 

 on four dates). 



Two other low-light cameras 

 were set at side windows to 

 provide data on locomotory ac- 

 tivity and swimming speeds. 

 Each viewed a 3.6-m wide sec- 

 tion of the opposite tank wall and about 4.6 m- of 

 bottom, and recordings were made for 5 min at the 

 beginning of each hour. An index of locomotory ac- 

 tivity was provided by the number of fish passing a 

 central line in view of the camera. Swimming speeds 

 (cm/sec) were determined by timing the passage of 

 fish between two points 142 cm apart on the tank 

 wall. Whenever possible, the gender offish passing 

 through this view was noted. The two cameras pro- 

 vided essentially identical information, and record- 

 ings from only one were analyzed for each day. 



Observations were also made on the relative abun- 

 dance of winter flounder larvae in the aquarium. 

 Flounder larvae were almost constantly present in 

 the aquarium after mid-February, and an index of 

 their abundance was recorded each day. Because the 

 larvae demonstrated diurnal vertical migration, ob- 

 servations were made at approximately 1200 h and 

 general abundance was scored from zero to four. A 

 score of one was recorded when only a few larvae 

 were observed in any field of view and a score of four 

 was given when thousands of larvae were present at 

 all of the tank windows. 



Field collections 



To monitor the location, reproductive condition, and 

 sex ratio of winter flounder in a wild population, 

 weekly daytime otter-trawl surveys were conducted 

 from 7 February to 24 April 1997 in the Navesink 

 Jliver estuary. New Jersey (Fig. 1), which is a known 

 spawning area for the species ( Scarlett' ). Eight fixed 

 stations were established approximately 1 km apart 



Figure 1 



The Navesink River estuary. New Jersey, showing the stations where collections were made 

 for winter flounder during winter and spring 1997. 



throughout the system. Two 5-min tows (at 4.4 ±0.9 

 km/h) were made at each station with a 5-m semi- 

 balloon otter trawl with 3.5-cm wings and body and 

 a 6-mm codend liner. Abundance of winter flounder 

 was reported in catch per unit of effort standardized 

 as number of individuals per 100 m of tow distance, 

 which was estimated with a global positioning sys- 

 tem (GPS). 



Winter flounder collected in the trawl surveys were 

 measured to the nearest millimeter of total length, 

 blotted dry, and weighed to the nearest gram. Gen- 

 der was determined by inspecting the gonads, and 

 each fish was classified as immature, ripe, or spent. 

 The gonads were weighed to the nearest gram, and 

 gonadosomatic indices (GSI ) were calculated accord- 

 ing to LeCren (1951) as 



GSI = 100 [gonad weight/total body weight). 



The stomach of each winter flounder was removed, 

 preserved in 10% formalin solution, and later trans- 

 ferred to 70'7f ethanol. Diet was analyzed as in Stehlik 

 ( 1993), and fullness of the foregut was estimated vi- 

 sually on a scale from 0% to 100%. Prey items were 

 identified to the lowest possible taxon and the pro- 

 portion of the total volume of stomach contents con- 



' Scarlett, P. G. 1991. Temporal and spatial distribution of win- 

 ter flounder ^ Pseudopleuronectes americanus) spawning in the 

 Navesink and Shrewsbury Rivers, New Jersey. Dep. of Envi- 

 ronmental Protection. Div. Fish. Game and Wildlife, Bureau of 

 Marine Fisheries, Nacote Creek Marine Fisheries Laboratory, 

 Star Route, Ahseron, New Jersey, 12 p. Unpubl. report. 



