Natural movements of 14 American eels Anguilla rostrata tagged with ultrasonic transmitters were monitored in the estuary of Calumet River, a tributary of the northern Gulf of St. Lawrence, Monitoring occurred hourly during each flood tide over half a full-moon cycle and half a new-moon cycle (from neap tide to spring tide) in August 1983 and 1984 (60 tides and 36 d tracking). Tides influenced movement frequency and distance, The fish were more active at night during both low and high tides. Their activity was greater during daytime high tides than nighttime low tides. Areas of activity were also greater during flood tides, particularly at night. Home ranges varied between 0.5 and 2.0 hectares. American eels consistently returned to the same stream section after linear movements of up to 800 m at high tide, Movements generally followed tidal flow: movements upstream or shoreward on flood tide brought American eels into regions of higher temperatures and lower salinities at high tide, Although midchannel temperatures were as low as 5°C and salinities were as high as 24%o, American eels generally selected salinities less than 12%o and temperatures higher than 15°C.
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Dutil et al. (1988) studied this question.