White grunts recruited into the fishery at 2 years. Maximum observed age of grunts was 18 years for females and 15 years for males. Substantial portions of the Toby Creek watershed, located in Clarion County, Pennsylvania, are severely acidified. AMD induced habitat fragmentation may limit fish movement by isolating subpopulations. Any catastrophic disturbance within the watershed may result in local extinction events leading to a population bottleneck and possible loss of genetic diversity.
Preliminary results using microsatellite markers also suggest a low level of genetic variation.
Whereas, samples from the reference watershed show relatively high levels of genetic diversity. Our results, although preliminary, suggest an unusually low level of genetic variation in fish inhabiting Toby Creek. This deficit may be the result of a severe population bottleneck, followed by genetic drift. Over the past decade the population has experienced a gradual decline in overall recruitment, and a shift towards dominance of the summer cohort. The difference in the timing of spawning results in a difference in length that persists through age one.