Diel spawning activity of red porgy (Pagrus pagrus: Sparidae) in North Carolina

Various fish species are known to focus spawning activity during particular times of day or night to maximize rates of fertilization and egg survival.  In this study we collected specimens of P. pagrus aboard commercial hook fishing vessels off of Cape Fear North Carolina during the main spawning season throughout daylight hours when the fish were actively caught.  For each specimen we macroscopically determined sex and maturity, calculated GSI and recorded time of day.  Median time of capture was 08:30 EST for ripe females 13:40 EST for developing females.  Mean time of day was significantly different between developing and ripe females (P < 0.001).  These data suggest that P. pagrus in North Carolina waters spawn primarily during morning daylight hours.  Investigators attempting to describe seasonal maturity cycles in this species should account for the time of capture so that diel variation does not confound seasonal variation.  The adaptive significance of morning spawning in this species is not clear, though daylight spawning is known to occur in species that have visual courtship displays.