Tidal and diurnal spawning cues in the atlantic silverside, Menidia menidia

Field and laboratory revealed tidal and diurnal cues for spawning inthe atlantic silverside, Menidia menidia . In the field, spawning runs began approximately when daytime flood tide velocities ranged from 3 to 16 cm sec super(-1). Spawning runs ended at ebb tide velocities ranging from 5 to 22 cm sec super(-1). Laboratory reared M. menidia were held in tanks. The seawater circulation pump was turned off twice daily for one hour, from 1200 to 1300 and 2400 to 0100. Current velocities decreased from 8.0 cm sec super(-1) to zero during these periods. M. menidia held under a 24 h light:0 h dark (24 L:0 D) photoperiod spawned from 1200 to 1300 and 2400 to 0100 in response to decreased current velocities. Modification of the photoperiod to 14 L:10 D resulted in spawning between 0500 and 0600 in response to "lights-on" and between 1200 and 1300 in response to decreased current velocities. No spawning occurred in response to the decreased current velocities during darkness.