Type of Document Dissertation Author Leaf, Robert Thomas Author's Email Address rleaf@vt.edu URN etd-08122010-063252 Title The Evolutionary Effects of Fishing: Implications for Stock Management and Rebuilding Degree PhD Department Fisheries and Wildlife Sciences Advisory Committee
Advisor Name Title Jiao, Yan Committee Chair Berkson, James M. Committee Member Hallerman, Eric M. Committee Member Murphy, Brian R. Committee Member Prager, Michael H. Committee Member Keywords
- Keywords: Japanese medaka
- Oryzias latipes
- aquaculture
- life-history evolution
- quantitative genetics
- heritability
- individual-based model
- fishery-induced evolution
Date of Defense 2010-06-22 Availability unrestricted Abstract Recent empirical studies have demonstrated inter-generational morphological and life-historychanges in fish stocks that have been impacted by size-selective harvest. Evolutionary processes
in biological populations occur through differential survival and reproductive success based, in
part, upon individual phenotypic variability. Fishing is a source of directional selection resulting
in the directed removal of some phenotypes; however, many aspects of the evolutionary effects
of fishing remain have yet to be described. In order to better understand the life-history and
morphological changes that occur as a result of size-selective fishing, and their effect on fishery
dynamics, I first determined the suitability of Japanese medaka (Oryzias latipes) for selection
experiments. I performed selection experiments using Japanese medaka and report how
morphology and life-history characteristics changed over multiple generations of selection. I
then used these patterns of change in life-history and morphology to validate individual-based
simulation candidate models to test general mechanisms of life-history relationships. Finally, I
applied the individual-based simulation modeling approach in order to describe how biological
and fishery characteristics change in a large, age-structured population exposed to size-selective
fishing over multiple generations. I found that the Japanese medaka has attractive characteristics
for biological investigation. The selection experiments indicated large changes in the age-atmaturity,
including a nearly 50% decrease over four generations in the most intense sizeselective
removal regimes. However, I did not observe significant changes in length-at-age or
weight-at-age over the course of the experiment. Candidate simulation models were poor at
predicting some aspects of the life-history characteristics of Japanese medaka. The simulation
model to determine fishery characteristics predicted large decreases in yield and egg production
as a result of decreases in length-at-age. Understanding the relationships of life-history
characteristics and their role in determining population resilience is a step toward understanding
the importance of evolutionary processes in fishery management.
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