Differences in growth and maturation of blacknose dace (Rhinichthys atratulus) across an urban-rural gradient

To investigate changes in the biology of blacknose dace (Rhinichthys atratulus) populations accompanying watershed urbanization, we sampled dace from four watersheds in the Baltimore, Maryland area, representing a gradient from urbanized to rural conditions. Dace from the most urbanized watershed grew to greater standard lengths during their first year of life when compared to dace from other watersheds but grew little during their second year. Dace from the other watersheds showed slower growth during their first year but continued to grow through age II Approximately 90% of age I dace from the most urbanized watershed were mature at age I, whereas only 25% of age I dace from the other watersheds were mature. Dace from the most urbanized watershed also reached maturity at shorter standard lengths than dace from the other watersheds. Growth and maturation of dace from the most rural watershed were similar to those reported for dace from other regions. We conclude that watershed urbanization results in increased growth rates of young blacknose dace, and in heavily urbanized (> 90% urban land use) watersheds, decreased age and size at maturity.