Editorial Type:
Article Category: Research Article
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Online Publication Date: 01 Dec 2002

Differences in Growth and Maturation of Blacknose Dace (Rhinichthys atratulus) across an Urban-Rural Gradient

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Page Range: 1122 – 1127
DOI: 10.1643/0045-8511(2002)002[1122:DIGAMO]2.0.CO;2
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Abstract

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.

Copyright: The American Society of Ichthyologists and Herpetologists
 Fig. 1. 
 Fig. 1. 

Location of study watersheds and sampling sites in relationship to the city of Baltimore, Maryland, and the Chesapeake Bay

 Fig. 2. 
 Fig. 2. 

Length frequency histograms for age I and II blacknose dace from four watersheds in the Baltimore metropolitan area. Age was estimated from thin-sectioned otoliths

 Fig. 3. 
 Fig. 3. 

Relationship between size of age I (A) and II (B) blacknose dace and percent watershed urbanization. Regression equations for lines are given on the graphs and are the result the regression of mean size (indicated with solid triangles) on percent watershed urbanization.

 Fig. 4. 
 Fig. 4. 

Percentage of mature blacknose dace as a function of standard length for four watersheds in the Baltimore metropolitan area. Lines are fitted logistic regressions. No line is included on the Herring Run graph because the probability of maturity was not significantly dependent on size

Received: 06 Feb 2001
Accepted: 02 Apr 2002
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