Fertilization Dates, Pelagic Larval Durations, and Growth in Gag (Mycteroperca Microlepis) from North Carolina, USA

Abstract

We estimated pelagic larval duration (PLD) and age from the otolith microstructure of post-larval and juvenile gag, Mycteroperca microlepis (Goode and Bean, 1879). These estimates were used to: (1) estimate spawning periods; (2) evaluate lunar periodicity in spawning; (3) assess relationships between PLD and fertilization date, ingress date, capture date, and size at capture; and (4) compare juvenile growth rates in two consecutive years and with rates determined in previous studies. Postlarval and juvenile gag were collected from late spring to early fall of 2007 and 2008 using a variety of gear types; otoliths from postlarvae collected in previous years were also examined. Estimated fertilization dates ranged from February to April with concentrations aligned with the first and third quarters of the lunar cycle. The mean PLD was approximately 45 d for fish collected as postlarvae or juveniles despite a 6 mo range of collection dates (April-September). The distributions of PLDs were similar among sampling months suggesting no effect of PLD on subsequent survival. Although there was no relationship between PLD and date of ingress, PLD was shorter for fish with later fertilization dates. Juvenile growth rates derived from length and estimated ages were approximately 1.4 mm d-1 during summer months and did not differ between years. Our findings support the timing (January-April) of fishing closures on aggregations of spawning gag in the southeast US and suggest that post-settlement survival is not linked to PLD