Diel feeding patterns: Stomach Volumes Change in feeding strategy over life cycle- diurnal nocturnal feeding Orpheus Island (n=99) One Tree Island (n=113) Dawn Mid-dayDusk DawnMid-dayDusk Mean Stomach Volume Juveniles (<120mm) Small Adults (120-160mm) Large Adults (160-200mm)
Number of Bites per 10 minutes Total Length (mm) Orpheus Island One Tree Island Diel Feeding Patterns: Daytime Feeding rates Observations: feeding rate in daytime r= -0.826 r= -0.697
Diurnal/ Nocturnal Distributions Diurnal/ Nocturnal Distributions REEF CREST Patch reef 10m 5m SAND 15m 30m Methods Created a fine scale map of reef section Surveyed 3x during the day 3x at night Hypothesis Distributions and habitat use may differ between day and night
Data pooled for n=3 nights Diurnal/ Nocturnal Distributions DAY (n=15) NIGHT ( n=13 ) REEF CREST Patch reef 10m 5m SAND 15m 30m 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