Temporal genetic variation of mitochondrial DNA and the female effective population size of red drum (Sciaenops ocellatus) in the northern Gulf of Mexico

We studied genetic drift of mitochondrial DNA (mtDNA) haplotype frequencies in a natural population of red drum (Sciaenops ocellatus) from the norther n Gulf of Mexico (Gulf). The amount of genetic drift observed across tempor ally adjacent year classes (1986-89) was used to estimate variance effectiv e (female) population size (N-ef). N-ef was estimated to be 14 308 and the ratio of female effective size to adult female census size was approximatel y 0.004, which is among the lowest value reported for vertebrate animals. L ow effective size relative to census size among red drum in the northern Gu lf may result from yearly fluctuations in the number of breeding females, h igh variance in female reproductive success, or both. Despite low genetic e ffective size relative to census size, the genetic effective population siz e of red drum in the northern Gulf appears sufficiently large to preclude p otentially deleterious effects of inbreeding.