Dietary composition and habitat preferences of Blueback herring, Alosa aestivalis, including observations on their role in the trophic ecology of Lake Chatuge NC/GA

Blueback herring, Alosa aestivalis, were collected during a 15-month period from Lake Chatuge, NC/GA, to determine food habits, evaluate sampling methods, and determine habitat preferences. Experimental and standard gill nets were fished horizontally, obliquely, and vertically at different depths, while electrofishing efforts employed 30-minute transects along designated shoreline areas. Larval light traps were fished at alternating sites and depths to sample available plankton and larval blueback herring. Blueback herring were determined to be obligate planktivores; the primary prey items included cladoceran species from the genera Daphnia, Bosmina, Chydorus, and Leptodora, calanoid copepods, and dipterans (chironomids, chaoborids, and ceratopogonids). The larger specimens also utilized aquatic insects as well as juvenile black basses (Micropterus sp.) and bluebacks. Piscivory was recorded from July through September 1998 and December 1998 with a peak in September (50% of sample, n=2, contained fish). Piscivory also occurred during 1999 in May (6.7% of all fish examined, n=30) and June (23.3%, n = 30). The best sampling method for blueback herring was gill netting with mesh sizes ranging from 0.95-2.54 cm. Electrofishing was effective only in mid-December when fish were in riverine portions of the lake. Only three larval blueback were collected in light traps during the study, proving that light traps were ineffective for collecting larval and juvenile blueback herring. Blueback herring were found to have an upper thermal preference of 25° C and can tolerate dissolved oxygen levels as low as 1.4 mg/L. as well as pH levels of 4.4.