Spawning Chronology of Native and Introduced Striped Bass (Morone saxatilis) in Two Gulf of Mexico Drainages

In this study, I investigated the potential for temperature to serve as a mechanism for maintenance of reproductive isolation in a sympatric population of Atlantic and Gulf striped bass in the Apalachicola and Ochlockonee rivers, Florida. Adult striped bass (n= 66, mean weight = 8.3 kg, mean total length = 780.6 mm) were collected from February to May below Jim Woodruff Lock and Dam, on the Apalachicola River, and below Jackson Bluff Lock on the Ochlockonee River, Florida. Ancestry (Gulf or Atlantic) of specimens was determined based upon the methods of Wirgin et al. (2005) using three diagnostic microsatellite loci: SB 20, SB 1021 and SB 111. There was no difference between the mean date of arrival for female striped bass between strains within years. The mean date of first arrival for either strain of striped bass differed between 2003 and 2005. A comparison of the mean arrival temperature for Atlantic and Gulf striped bass also showed no difference within years. It is possible that the genetic introgression of Atlantic alleles has been so great that any difference in spawning temperature preference between strains that might have existed historically has been lost