Life History of Menhadens in the Eastern Gulf of Mexico

Abstract

Biological material collected with plankton and gill nets during cruises of the R/V George M. Bowers in the eastern Gulf of Mexico indicated that menhadens spawned principally near shore from November through March. Two species of menhaden—Gulf menhaden (Brevoortia patronus) and yellowfin menhaden (B. smithi)—and their hybrid abounded in collections during the winters of 1964 through 1967. Gulf menhaden, the most important commercial species, occurred throughout the study area but its numbers decreased to the east and south. Yellowfin menhaden were confined to the coastal region of peninsular Florida, whereas hybrids were taken only from Tampa Bay south to Cape Sable. Hybrid menhaden apparently backcross freely with the parental species but the extremely high percentage of hybrid males (≥99%) assures against establishment of a hybrid population. The likelihood of natural hybridization and introgression was substantiated by artificial fertilization experiments. In addition to the menhadens, six other clupeids entered the combined collections. Three of these species—Atlantic thread herring (Opisthonema oglinum), scaled sardine (Harengula pensacolae), and Atlantic round herring (Etrumeus teres)—have spawning seasons that coincide, in part, with that of the menhadens. The early life stages of these species, although undescribed, were probably represented in the plankton collections.