Genetically Inferred Reproductive Behavior in Captive Guadalupe Bass

Guadalupe Bass (Micropterus treculii), a Texas endemic and species of special concern, were collected from the South Llano River (n = 281) for use as broodfish in a restoration effort.  Reproductive behavior in captivity was monitored by typing production offspring with 17 microsatellite loci and resolving parentage.  The first two spawning seasons (2011, 2012) indicated low levels of male participation (34%, 28%), a highly asymmetric sex ratio (M:F; 1:2.33, 1:1.93), and high levels of polygyny (90%, 80% of spawning males), resulting in a relatively small effective number of breeders (N_b; 32.2, 41.7).  These observations departed from the documented mating systems of wild congeners and prompted modifications to the spawning environments.  The third spawning season (2013) resulted in greater levels of male participation (52%), a more symmetric sex ratio (1:1.55), and decreased levels of polygyny (69% of spawning males), resulting in a dramatic increase in N_b (91.6).  Behavioral differences over time were associated with greater numbers of penned fish, increased broodfish size, reduced broodfish size variance, modifications to spawning compartments, and supplementation of the broodstock with wild individuals, but acclimation time and increased age appear to account for most of the changes in reproductive behavior and the resultant increase in N_b.