Are Atlantic goliath grouper, Epinephelus itajara, establishing more northerly spawning sites? Evidence from the northeast Gulf of Mexico

Abstract

Many fish migrate long distances to form spawning aggregations—important life history events that reflect population reproductive potential—often at predictable times and places. However, we often do not know where and when aggregations form, or if they are characteristically similar across spatial gradients. For Atlantic goliath grouper, Epinephelus itajara (Lichtenstein, 1822), spawning aggregations have been verified from subtropical sites off the southeast and southwest coasts of Florida, and off the southern coast of Brazil. Here, we verify a spawning aggregation off the northwest Florida coast in warm temperate waters of the Gulf of Mexico and characterize the aggregation relative to those in south Florida. Evidence of a spawning aggregation was derived from seasonal differences in gamete stages, nocturnal sound production, and relative abundance on the presumed aggregation site. These patterns all paralleled those of south Florida spawning aggregations, but with a shorter spawning season. In northwest Florida, there was a spatiotemporal relationship with reproductive timing and surface water temperature, and with wind speed/water current direction, which indicate that timing of goliath grouper reproduction is optimal for larval transport and survival. This northwest Florida spawning aggregation is significant because it represents an expansion of approximately 3° farther north than previously verified aggregations.