Abstract
The influence of early life development on the swimming performance of the endangered sofie Chondrostoma toxostoma was examined to highlight trends in organism‐environment relationships. Sudden occurrences of change in integrated function were found and these were most decisive, in particular with respect to microhabitat use, between the larval and juvenile periods of development. Stabilization of relative growth, i.e . end of the remodelling process (metamorphosis), occurred well after all larval characteristics (remnants of finfold and rapid allometric growth) had disappeared and all juvenile structures had appeared (nasal septa and complete scale cover). The fact that stabilization of relative growth coincided with dramatic shifts in microhabitat use (organism needs) as well as in swimming capacity (organism skills) suggests a more ‘decisive’ type of change in organism‐to‐environment interaction than one purely of form, i.e . shift from nursery to adult habitat.