Daily and seasonal movements of adult alewives, Alosa pseudoharengus, were studied at depths of 5 to 18 m in Indiana waters of Lake Michigan near Michigan City. Collections were made June to October, 1971, with gill nets and a bottom trawl and June to September, 1972, with gill nets.There was no significant difference (P > 0.05) between trawl and gill net catch rates in 1971 regardless of time of day. Significantly more fish were caught during early summer than late summer. Noon gill net catches did not differ significantly between stations. At 10 m, midnight gill net catches were larger than noon catches and bottom gill net catches were greater than surface catches.In 1972, June and July gill net catches were greater than August and September catches. Spawning was essentially completed by August, and inshore populations of spawning adults returned to deeper offshore areas.Midnight catches were greater than noon catches at all depths. During the day, alewives were farther offshore than the 15 m station, but at night they moved inshore. Crowding of alewives inshore at night resulted in significantly larger catches at the 5 m than at the 15 m station.Food habit studies in 1971 and 1972 revealed zooplankton comprised the major portion of the alewife diet. The copepod Cyclops bicuspidatus was the main zooplankter consumed. Bosmina longirostris and Eurycercus lamellatus were major cladoceran food items. Major non-zooplankton food items were Cryptochironomous, Chironomous, and larval alewives.Zooplankton and cladoceran percent volume in stomachs increased to maxima in July of each year followed by a general decline. Copepods were the dominant food in June. Chironomid larvae were a major component of the diet in May, 1972, and August of both years. The largest percent volume of alewife larvae in stomachs occurred in September.A comparison of daily movements and food habits by percent composition of food items in alewives collected July, 1971, revealed the dominant zooplankton species in alewife stomachs were Bosmina longirostris, Chydorus sphaericus, Alona affinis, Eurycercus lamellatus, Polyphemus pediculus, Cyclops,bicuspidatus, and Limnocalanus macrurus. B. longirostris and P. pediculus, which accumulate at the surface at night, were consumed by alewives in greatest quantity at midnight and sunset when the alewife is near the surface. The benthic species C. sphaericus, A. affinis, and E. lamellatus were consumed in greatest quantity at sunrise when the alewife is near the bottom.Ball State UniversityMuncie, IN 47306
| Identifer | oai:union.ndltd.org:BSU/oai:cardinalscholar.bsu.edu:handle/180692 |
| Date | 03 June 2011 |
| Creators | Webb, Darrel A. |
| Contributors | McComish, Thomas S. |
| Source Sets | Ball State University |
| Detected Language | English |
| Format | ix, 104 leaves : ill. ; 28 cm. |
| Source | Virtual Press |
| Coverage | n-us-in |
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