Diel activity cycles of two Chesapeake Bay fishes,the striped blenny (Chasmodes bosquianus) and the oyster toadfish (Opsanus tau)

Diel activity cycles of toadfish and striped blennies were identified in the laboratory by means of mechanoelectric detector units. Data for both species were collected over 72-h periods. Daytime and nighttime activity rates were compared statistically. In addition, five 3-h segments (3 during the day and 2 at night) were selected for statistical comparison. both species are more active at night than during the day. The toadfish appears to be more strictly nocturnal than does the blenny, with the peak in its activity occurring in the 3-h segment following dusk. Blenny activity increases throughout the night, reaching a peak during the 3-h segment before dawn. It then ebbs to a low in the afternoon.