The effects os salinity and photoperiod on the diel activity pattern of mummiichogs (Fundulus heteroclitus)

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University of New Brunswick


The diel cycle of activity varies among fishes. Some species show nocturnal activity, while others are diurnal or crepuscular. The diel period where fish are most active has important relationships to the species’ niche and life history. Mummichogs (Fundulus heteroclitus) are ecologically important yet their diel cycle patterns are not well understood. Some studies report a diurnal pattern while others report a nocturnal pattern. To resolve this discrepancy, and better understand influences on the diel activity cycles of mummichogs, I investigated the effect of photoperiod and salinity on the day and night activity levels of mummichog. Mummichogs were acclimated to sea water (35ppt) or half-strength sea water, (17ppt) and their diel activity was measured after acclimation to winter (10L:14D) photoperiod and again after acclimation to summer photoperiod (12L:12D). Salinity and photoperiod had no significant effect on the diel activity pattern of mummichogs. Mummichogs maintain similar activity levels at all times.