Meeting Abstract

58.6  Thursday, Jan. 6  Do bluegill ecomorphs differ in steady swimming performance and energy economy? ELLERBY, DJ*; GERRY, SP; Wellesley College dellerby@wellesley.edu

Ecomorphs, distinct morphological types associated with particular habitats, have been identified within many fish populations. Phenotypic plasticity in response to a variable environment has long been recognized as a potential factor in the adaptation of populations and in macroevolution. An essential step in understanding the potential role of plastic traits in adaptive divergence is an assessment of their effects on performance, and ultimately fitness. Few studies have quantified and compared locomotor performance in fish ecomorphs. We have quantified steady swimming performance, kinematics and aerobic energy costs in littoral and pelagic ecomorphs from a bluegill sunfish (Lepomis macrochirus) population in Lake Waban, MA, USA. The pelagic ecomorph has higher aspect ratio pectoral fins, and a more fusiform body shape than the littoral form, features associated with effective labriform (pectoral fin powered) cruising and low body drag. We hypothesized that pelagic fish would have a higher gait transition speed from labriform to undulatory swimming, a longer stride length and a lower cost of transport at this speed relative to the littoral form. Gait transition speed was significantly higher in the pelagic ecomorph (0.84 ± 0.05 vs. 1.10 ± 0.04 body lengths s^-1), as was stride length (0.37 ± 0.02 vs. 0.29 ± 0.02 body lengths) and the cost of transport at this speed was significantly lower (3.61 ± 0.27 vs. 5.13 ± 0.43 J kg^-1 m^-1), confirming that the pelagic morph is a more effective and economical labriform swimmer. A companion study has compared maneuvering performance in the two ecomorphs. Data are shown as mean ± SEM. Significant differences (P<0.05) were detected by t-tests.