Abstract:
Possible differences in food consumption, growth, and food conversion comparing groups of six bluegill (Lepomis macrochirus) to six hybrid sunfish (male bluegill x female green sunfish (Lepomis cyanellus) ) were evaluated over a 64 day total period from December 12, 1991 to February 14, 1992. Each fish was held in an individual aquarium with a daily 12 hour photoperiod of natural light supplemented with overhead fluorescent lighting. Daily maximum and minimum water temperatures ranged from 58 to 69°F. Fish were fed an ad libitum, ration of frozen brine shrimp (Artemia sp.) twice daily between 0700-1000 hours and 1600 -1900 hours. The 64 day total period was divided into sequential 22, 20, and 22 day periods with fish weighed and measured at the beginning and at the beginning and end of each period. Examination of data revealed a significant difference (t-test; P<0.05) in the amount of food consumed for all periods with bluegill consuming more food than hybrid sunfish. There were no significant differences observed between bluegill and hybrid sunfish in conversion efficiencies for any of the three experimental periods (t-test; P>0.05). Evaluation of weight gain and length gain per day revealed no significant differences (t-test; P>0.05) except in period 1 with bluegill growing more than hybrid sunfish. These results must be interpreted with care since fish were isolated and social mechanisms excluded. Social interactions appeared to have some importance in the feeding behaviors of the fish, particularly the hybrid sunfish. A follow up test using all twelve of the original experimental fish together in the main raceway tank provided insight into this phenomenon.
