Diel spawning periodicity of red snapper Lutjanus campechanus in the northern Gulf of Mexico

Ovaries of red snapper Lutjanus campechanus were examined histologically to determine rates of oocyte maturation, diel spawning periodicity and whether lunar cycle influenced spawning rhythm. Hydration of red snapper oocytes began during the mid‐morning hours; c. 5 h was necessary for oocytes to become fully hydrated and ovulation occurred no more than 5 h after oocytes attained full hydration. Appearance of fresh postovulatory follicles after 1330 hours and the absence of hydrated oocytes after 1830 hours signified that red snapper spawning occurred during this 5 h period. In addition, evidence of a peak in spawning was seen near 1600 hours. Postovulatory follicles degenerated within a 24 h time period. A lunar spawning cycle was not evident.