KERFOOT, J.R.*; SCHAEFER, J.F.; Florida Institute of Technology; Southern Illinois University Edwardsville: Microhabitats and Ecomorphologies of Cottus species

Phenotypes of fishes act as fundamental constraints upon their ecologies; morphology shapes ecological attributes through its effect on performance. Field and laboratory studies were conducted to investigate the relationships between morphological attributes and microhabitat use in Cottus populations. Field studies revealed significant differences between Ozark and Prairie stream microhabitats where populations of Cottus species occurred. Features of the microhabitat that were characteristic of each stream type correlated with intra- and interspecific differences in morphological attributes of Cottus. The morphology of Cottus occurring in the deeper, slower, and more silty Prairie stream had larger head width and depth, body width and depth, and caudal peduncle width; whereas those occurring in a shallower, faster flowing Ozark stream had longer pelvic fins, larger eyes, and deeper caudal peduncles. Each population had a morphology tailored to optimize their performance in a certain habitat. Results of laboratory based performance studies using a variable flow chamber revealed that Critical Current Velocities (CCVs) of live and preserved specimens correlated with distinct combinations of morphological traits. Those specimens having higher CCV measurements typically had longer pelvic fins, larger eyes, and deeper caudal fins (Ozark morphology), and those with lower CCVs had larger head width and depth, body width and depth, and caudal peduncle width (Prairie morphology). Differences in flow regimes between Prairie and Ozark streams generate specific niches for specific morphotypes. Current velocity may exert selective pressure on morphology.