The Evolutionary Effects of Fishing: Implications for Stock Management and Rebuilding

Recent empirical studies have demonstrated inter-generational morphological and life-history changes 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.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Fisheries and Wildlife Sciences

Department dc:contributor.department

Fisheries and Wildlife Sciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2010

Author dc:creator

• Leaf, Robert Thomas

Chair dc:contributor.committeechair

• Jiao, Yan

Committee members dc:contributor.committeemember

• Hallerman, Eric M.
• Murphy, Brian R.
• Berkson, James M.
• Prager, Michael H.

• Japanese medaka
• Oryzias latipes
• aquaculture
• life-history evolution
• quantitative genetics
• heritability
• individual-based model
• fishery-induced evolution

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-08122010-063252

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/28636