Behavior of Larval Yellowcheek Darters Relative to Current and Light

We wanted to examine the response of larval Yellowcheek Darter to current and light. Two age classes were place in a circular flume with a gravel bottom.  Vertical height was observed as current was increased from zero to 2.85 cm/s in six steps.  Larvae 1-3 dph maintained a position at the surface regardless of current.  Larvae 28-34 dph moved deeper in the water column as current increased.  Groups of six larvae were placed in a rectangular chamber (43 cm long x 10 cm wide x 10 cm deep) and held in the dark for 5 or 15 min. A chemical light stick was added and larvae were allowed to acclimate for 5 or 15 min.  The chamber was divided and the number of larvae in each side of the chamber was recorded.  Larvae preferred the lighted end of the chamber (Χ²=1022.7, P<0.001).  We hypothesize that wild larvae emerge from riffle gravel the morning after hatching and are advected to a contiguous downstream pool, where current slows and larvae move horizontally seeking refuge along pool margins. Based on the behavior of larval Yellowcheek Darter, larval light traps would be a reasonable sampling gear for testing our hypothesis regarding larval behavior.