The reproductive characteristics, movement patterns and courtship behaviors associated with a yellowfin grouper (Mycteroperca venenosa, Linnaeus, 1758) fish spawning aggregation (FSA) were assessed between 2004 and 2014. The FSA was located on the Grammanik Bank, a seasonally
closed area on the edge of the Puerto Rico platform, south of St. Thomas, US Virgin Islands. Fish arrived at the FSA site around full moon and departed 10–12 days after full moon (dafm), during two or three consecutive months, from January to May each year. Males were significantly larger
than females and preceded females at the spawning site. Courtship coloration and behaviors showed distinct patterns relative to lunar date and time of day. Spawning was observed for several days each month in 2008, 2009, 2011 and 2014, from 6 to 10 dafm. Female gonadosomatic index (GSI) values
were highest from 4 to 7 dafm. Spawning, which began at sunset, consisted of 7 to 12 males following one female along the bottom before ascending 10–20 m, then "rushing" upward to release gametes. Histological analysis of ovaries indicated females spawned every 2–3 nights, although
11.6% were capable of spawning two consecutive nights. Total spawning population size of yellowfin grouper fluctuated from 600 to 1100 fish during the study period, but consistent annual population assessments using scuba were difficult to carry out due to ocean conditions. Based on size-frequency
analysis and other metrics, the M. venenosa spawning population at the Grammanik bank appears to be stable at this time with existing regulations.
Do Not Stop: The Importance of Seamless Monitoring and Enforcement in an Indonesian Marine Protected Area
