Date Awarded

1971

Document Type

Thesis

Degree Name

Master of Science (M.Sc.)

Department

Virginia Institute of Marine Science

Advisor

Jackson Davis

Committee Member

Mark E. Chittenden

Committee Member

George Grant

Abstract

More than 750 white perch, Morone americana, were collected from each of two major tributaries of southern Chesapeake Bay to compare the age structures, growth rates, and mortality rates of the two populations.The James River is characterized by heavy domestic and industrial pollution, whereas the York River is only slightly polluted. Maximum ages determined by scale analysis were 7 and 10 years for males and females respectively in each river. Males and females from the James River were larger than those from the York up to ages IV and V, respectively. Older fish were larger in the York . Females from both rivers were larger and heavier than males at all ages. Length increments of both sexes were greatest early in life. Males predominated in young age groups but females were more abundant at age IV and older. An analysis of relative age frequency suggested dominant year-classes in 1964 and 1965 in the James River, but the 1968 year-class was weak. No dominant year-classes were apparent from the York River collections. Growth histories for white perch are similar in the two estuaries and show constant yearly growth increments for different year-classes at corresponding ages. Mortality rates were calculated from age frequency distributions. Total annual mortality in the James River was about 70% for males after age IV and for remailes after age VI. In the York River, males at age III and older die at a rate of about 59%, whereas females older than age V have an annual mortality of 57%. This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia.

DOI

https://doi.org/10.25773/RJ3X-KK97

Rights

© The Author

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