Science Serving Maryland's Coasts

R/FISH-98 a

Intrapopulation Biodiversity, and Recruitment Pathways for Chesapeake Striped Bass

Principal Investigator: 

Thomas J. Miller

Start/End Year: 

2009 to 2012

Institution: 

Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science

Co-Principal investigator: 

Allen Place, Center of Marine Biotechnology, University of Maryland Biotechnology Institute; David Secor, Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science

Topic(s): 

Strategic focus area: 

Sustainable natural resources of coastal Maryland

Description: 

*This project is a continuing project initially funded through award NA05OAR4171042 (year one) and currently funded through award NA10OAR4170072 (year two)*

OBJECTIVES: Our work seeks to test three fundamental hypotheses relating to the importance of intrapopulation biodiversity in spawning and early life history dynamics to the resilience of exploited natural resources using striped bass as a model population. The objectives include: 1) Does reproductive diversity influence recruitment potential? 2) Does phenotypic selection during early life cause the representation of maternal lines in the egg and juvenile stages to differ? 3) Do striped bass early YOY undergo deliberate retentive or dispersive behaviors resulting in two broadly classified contingents corresponding to two modalities in nursery habitat use?

METHODOLOGY: We will address our objectives by combining traditional approaches to studying the early life history of fish with those from the field of otolith microchemical analysis and modern molecular genetics. All work will be based on existing samples collected from the Patuxent River in 2007, and new sampling proposed herein for 2009. We will address the first two objectives characterizing sibship groups in eggs and later life stages in both 2007 and 2009 to test specific hypotheses regarding the maternal diversity, egg production and recruitment. This work requires application of maternal typing using techniques developed with existing MDSG PD funds that involves amplified, sequenced mtDNA isolated individual eggs, larvae and juveniles. The third objective requires microchemical analysis of otolith structure and birthdate frequency analysis. We have experience with application of all proposed protocols and laboratory techniques.

RATIONALE: When appropriately managed, the resiliency of Chesapeake's living resources to anthropogenic stress and climate change is remarkable. For example, striped bass is a dramatic success story of species recovery. But, although not realized at the time, the strong recruitments that lead to this success relied on the diversity in age structure within the population. We argue that biodiversity within population's genetic, demographic and complex life cycles of which striped bass serves as an example, is an overlooked but central factor in promoting population resiliency. Moreover, as anthropogenic stresses on all living resources in the Chesapeake Bay and other coastal ecosystems are likely to increase in the future, it is important that we seek to understand how such intra-population variability contributes to sustainability and resiliency in the resources. Here, we seek to quantify the contribution of intra-population diversity among the characteristics of spawning females and their offspring on population resilience using striped bass as a model species.

Impact/Outcome: 

This section describes how this project has advanced scientific knowledge and/or made a difference in the lives of coastal residents, communities, and environments. Maryland Sea Grant has reported these details to the National Oceanic and Atmospheric Administration (NOAA), one of our funding sponsors.

RECAP: Using striped bass as a model, this completed study employed traditional fisheries science approaches, combined with state-of-the-art chemical analyses and molecular genetics, to quantify the role of diversity in population resilience among spawning females and their offspring.

RELEVANCE: Back from the brink after a fishing moratorium, striped bass tell a dramatic success story of species recovery. The researchers in this study examined the diversity in age structure within the population and its role in the population’s recovery. As stress on living resources in the Chesapeake Bay and other coastal ecosystems increases, it is important to understand how such intra-population variability contributes to the sustainability and resiliency of fish populations.

RESPONSE: The principal investigators on this completed study are Thomas J. Miller and David Secor of the Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, and Allen Place, Institute of Marine and Environmental Technology, University System of Maryland. The researchers examined, among other questions, whether reproductive diversity influences recruitment (the number of new young fish surviving to enter the adult population.)

RESULTS: The researchers became the first group to sequence the entire striped bass mitochondrial genome. Based on this sequence, they have conducted an analysis that confirmed that the temperate sea basses are all descendants of a common ancestor.

The results suggest that despite the existence of high variation in egg phenotype (and presumptively, maternal phenotype) in the population, no particular phenotype appears to lead to greater reproductive success.

The researchers classified striped bass into resident (individuals that remained in freshwater habitats of salinity = 3) and migratory contingents (those that dispersed to brackish water habitats of salinity > 3). Most migrants dispersing down-estuary from freshwater natal habitats did so during the juvenile period. Migratory choices were influenced by early growth, which, in turn, was influenced by the date of hatch. Residents experienced accelerated early growth relative to most migrants and tended to have later hatch dates, suggesting better early conditions for larvae as the spawning season progressed. The trophic position, post-migration growth, and trophic niches of juveniles did not differ between habitats.

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