Diel Behaviour and Distributions of the Monocle Bream

Diel Behaviour and Distributions of the Monocle Bream (Scolopsis bilineatus)

Nemipterids- the forgotten fishes

Diel feeding patterns: Stomach Volumes Juveniles (<120 mm) Small Adults (120 -160 mm) Mean Stomach Volume Large Adults (160 -200 mm) Dawn Mid-day Dusk Dawn Orpheus Island (n=99) Change in feeding strategy over life cycle- diurnal Mid-day Dusk One Tree Island (n=113) nocturnal feeding

Using Observations

Diel Feeding Patterns: Daytime Feeding rates Number of Bites per 10 minutes Observations: feeding rate in daytime r= -0. 697 r= -0. 826 Total Length (mm) Orpheus Island One Tree Island

Diurnal/ Nocturnal Distributions 10 m 5 m Hypothesis Distributions and habitat use may differ between day and night 15 m AND 30 m REEF CREST D SAN S Patch reef Methods Created a fine scale map of reef section Surveyed • 3 x during the day • 3 x at night

Diurnal/ Nocturnal Distributions 10 m DAY (n=15) 5 m 15 m D 30 m REEF CREST SAN D SAN Patch reef

Diurnal/ Nocturnal Distributions 10 m DAY (n=15) 5 m NIGHT (n=13) 15 m 30 m REEF CREST D SAN Patch reef Data pooled for n=3 nights Adults moved away from reef and onto sand at night.

Implications Size matters! • Diel feeding patterns differed with age and growth • A demographic perspective is essential Shelter sites are important • Adult fish dependent on shelter microhabitats (with site fidelity) Diurnal/nocturnal distributions differed • Highlights importance of nocturnal surveys • Nocturnal fishes likely to be overlooked/underestimated historically Nocturnal feeders form important trophic links • Abundant nocturnal feeders such as Scolopsis bilineatus may play important roles in energy and nutrient cycling