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چکیده
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Alewife (Alosa pseudoharengus) were sampled as part of an ongoing study on juvenile production to determine diet through analysis of stomach contents. Alewife were sampled by pelagic purse seine and stored on ice or in 95% ethanol. Stomach contents were identified to genus. Preliminary work has identified stomach contents of 40 small alewives (≤70 mm) in Upper Mystic Lake (Massachusetts) and Highland Lake (Maine) from September 2016. Two zooplankton orders including Copepoda and Cladocera were the major food items consumed by alewife. Diets consisted primarily of Epischura, Cyclops, Mesocyclops and Tropocyclops (Copepoda) and Bosmina and Daphnia (Cladocera). In total 9 genera, 6 families and 2 phyla were identified in stomach contents. Bosmina was the most frequently identified prey taxon in Highland (89%) and in Upper Mystic (74%) and Thermocyclops was the least abundant in stomach contents of fish from Highland (0.13%) and Upper Mystic (0). There was no significant difference in abundance of Bosmina and Cyclops between Highland and Upper Mystic, but t-tests of the other genera between the two lakes were significantly different (p<0.05). The Shannon-Weiner index (species richness) was 0.65±37 and 0.86±27, and the Margalef index (species diversity) was 1.49±0.28 and 1.257±0.082 for Highland and Upper Mystic, respectively. Thus, initial findings suggest that diet items were relatively similar among these 2 lakes late in the year, although there were differences in the total numbers of each prey item. These findings will help interpret any growth and productivity differences among ponds in the northeastern United States.
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