Differential survival of fathead minnows, Pimephales promelas, as affected by copper exposure, prior population stress, and allozyme genotypes

Abstract

AbstractTwo populations of fathead minnows (F1, offspring of survivors of an acute fluoranthene exposure; N1, naive hatchery fish born in outdoor ponds) were concurrently exposed to approximately 850 μg/L of copper for 132 h. During the exposure, 49% of the F1 and 85% of the N1 minnows died. A curled operculum deformity, detected in 54% of the F1 population, was significantly related to mortality. A failure time regression model, combining both the F1 and N1 populations together, was fit to examine the relationship between population type (F1 or N1), body condition (weight/length3), presence of an operculum deformity, and different allozymes on time to death (TTD). The model indicated that type of population, body condition, the presence of an operculum deformity, and three loci (GPI‐1*, IDHP‐1*, and MDH‐2*) were significantly related to TTD. The F1 minnows had a higher survival rate and longer average TTD compared to N1 minnows. In comparison to the N1 population, the F1 population possessed a higher frequency of genotypes associated with increased survivorship at the IDHP‐1* and MDH‐2* loci. Weight (and body condition) was negatively correlated with survivorship. Minnows with a severe operculum deformity, believed to be a result of parental exposure to fluoranthene, had a 100% mortality rate and exhibited a considerably reduced TTD compared to nondeformed minnows. Multilocus heterozygosity was not related to TTD for either population. This study indicates that genetic factors may exhibit stronger effects on survivorship than other factors (e.g., weight/body condition) commonly associated with fitness.