EVALUATION OF 3 TYPES OF ARTIFICIAL HABITATS FOR FISHES IN A FRESH-WATER POND IN MAINE, USA

Three types of artificial structures (brush bundles, cinder blacks, ti re bundles) were studied along transects in Lac D'or, a boreal, freshw ater pond in central Maine. Observations were made of 1,397 adult and juvenile fishes by means of 18 dives during the day and 6 dives during the night in 1990. Cover attracted the five species of fishes in the pond (pumpkinseed, Lepomis gibbosus; chain pickerel, Esox niger; brown bullhead, Ameiurus nebulosus; common shiner, Luxilus cornutus; and go lden shiner, Notemigonus crysoleucas). Numbers of fishes were signific antly higher in areas with artificial cover (70% of fishes, average co unts per transect), or in areas with natural weed beds (29%) than in a reas without cover (1%). Pumpkinseeds were distributed about equally i n areas with tire bundles (38%), cinder blocks (34%), and brush bundle s (28%), whereas golden and common shiners were attracted primarily to brush bundles (62%). Numbers of fishes associated with artificial hab itat were significantly higher al night. Common and golden shiners occ upied locations on the periphery of structures, whereas pumpkinseeds f requently inhabited recesses of cinder blocks and brush bundles. Assoc iations with artificial habitat decreased rapidly in October when wate r temperature declined to below 12 degrees C. By early November, as wa ter temperatures decreased to 7 degrees C, fishes moved to the bottom, away from cover, and markedly reduced their movements. Artificial hab itats were re-examined in June 1991 following winter ice cover. All st ructures remained intact, except several branches from submerged brush bundles had been removed by animals, probably beaver Castor canadensi s (Castoridae). Although artificial habitat may only serve to redistri bute fishes in a lake or pond, such structures are recommended as a lo ng-term option for freshwaters where cover limits carrying capacity of fishes.