pattern. A total of 588 American eels were captured, 

 83% more than in the 24-h experiment, possibly 

 reflecting the intensity of foraging activity just after 

 sunset. To characterize the population, eels caught 

 on the third evening were measured. They had an 

 average total length of 30.7 cm (SD = 5.4, n = 121), 

 and 10 of the 121 animals caught had the silvered 

 pigmentation pattern which characterizes maturing 

 individuals (Tesch 1977). 



These data show that the foraging activity of 

 estuarine American eels in late summer through 

 autumn is nocturnal and peaks sharply at nightfall. 

 Whether the subsequent decline in captures was 

 caused by a decrease in foraging because of satia- 

 tion or by an unrelated decline in locomotor activity 

 cannot be determined. The swimming activity of 

 unfed eels in the laboratory often exhibits a dramatic 

 peak at lights-off (Bohun and Winn 1966; Edel 1976; 

 van Veen et al. 1976). Spring and autumn captures 

 of wild short-finned New Zealand eels, Anguilla 

 australis schmidtii, in baited traps displayed the 

 nocturnal activity pattern described here (Ryan 

 1984). However, capture patterns in the latter study 

 changed with the season, as did the locomotor pat- 

 terns of the yellow European eel, Anguilla anguilla, 

 studied by Westin and Nyman (1979). Further 

 research is required to understand the relationship 

 between foraging and locomotor activity patterns 



40-| 



X 



o 



< 30- 

 O 



< 



o 



20- 



UJ 



O 10- 

 K 



U 



N = 588 



17=45 18 : 45 



TIME OF DAY 



19 = 45 



Figure 2.— Percentage of total catch of American 

 eels by time of day for the evening experiment. The 

 histograms cover the time between checks; i.e., 

 right boundaries mark the times when traps were 

 checked. The bold section of the x-axis denotes the 

 period after sunset. 



and how environmental and physiological factors 

 might influence them. 



Literature Cited 



BlANCHINI, M., P. W. SORENSEN, AND H. E. WlNN. 



1981. Horseshoe crabs as bait for estuarine American eels, 

 Anguilla rostrata. J. World Maricul. Soc. 12:127-129. 

 Bohun, S., and H. E. Winn. 



1966. Locomotor activity of the American eel (Anguilla 

 rostrata). Chesapeake Sci. 7:137-147. 

 Edel, R. K. 



1976. Activity rhythms of maturing American eels (Anguilla 

 rostrata). Mar. Biol. 36:283-289. 



Fahay, M. P. 



1978. Biological fisheries data on American eel, Anguilla 

 rostrata (LeSueur). Natl. Mar. Fish. Serv. Sandy Hook 

 Lab., Highlands, NJ, Rep. 17, 87 p. 



Helfman, G. S., D. L. Stoneburner, E. L. Bozeman, P. A. 

 Christian, and R. Whalen. 



1983. Ultrasonic telemetry of American eel movements in a 

 tidal creek. Trans. Am. Fish. Soc. 112:105-110. 



Helfman, G. S., E. L. Bozeman, and E. B. Brothers. 



1984. Size, age and sex of American eels in a Georgia river. 

 Trans. Am. Fish. Soc. 113:132-141. 



Ryan, P. A. 



1984. Diet and seasonal feeding activity of the short-finned 

 eel, Anguilla australis schmidtii, in Lake Ellesmere, Canter- 

 bury, New Zealand. Environ. Biol. Fishes 11:229-234. 



Tesch, F.-W. 



1977. The eel. Chapman and Hall, Ltd., Lond./J. Wiley & 

 Sons, N.Y., 434 p. J. Greenwood, translator. 



Van Veen, T., H. G. Hartwig, and K. Muller. 



1976. Light-dependent motor activity and photonegative 



behavior in the eel (Anguilla anguilla L.). J. Comp. Physiol. 



111:209-219. 

 Westin, L., and L. Nyman. 



1979. Activity, orientation, and migration of Baltic eel (An- 

 guilla anguilla L.). Rapp. P. -v. Reun. Cons. int. Explor. 

 Mer 174:115-123. 



Peter W. Sorensen 



Graduate School of Oceanography 



University of Rhode Island 



Narragansett, RI 02882 



Present address: 



Zoology Department 



University of Alberta 



Edmonton, Alberta T6G 2E9, Canada 



Marco L. Bianchini 



Graduate School of Oceanography 



University of Rhode Island 



Narragansett, RI 02882 



Present address: 



I.P.R.A., Consiglio Nazionale Delle Ricerche 



Via Nizza 128 



00188 Roma, Italy 



Howard E. Winn 



Graduate School of Oceanography 

 University of Rhode Island 

 Narragansett, RI 02882 



747 



