Andrew O. (Ole) Shelton


Postdoctoral Scholar - Mangel Lab
Center for Stock Assessment Research (CSTAR)
University of California, Santa Cruz
ashelton(at)soe.ucsc.edu

I'm a marine biologist broadly interested in the life-histories of organisms and the connections between life-history, populations, and communities. I combine observational, experimental, and genetics data collected from natural populations with mathematical models to investigate the causes and consequences of life-history variation. I am particularly interested in the consequences of sex differences in life-history and the application of two-sex models to populations.

I am currently a postdoctoral researcher with Marc Mangel at UC Santa Cruz working on a variety of quantitative fisheries topics.

 

 

Doctoral Research

I received my Ph.D in 2009 from the Department of Ecology and Evolution at the University of Chicago (advisor Dr. Cathy Pfister). My dissertation focused on the causes and consequences of skewed sex ratios in natural populations of two marine plants (surfgrass; Phyllospadix spp.). Surfgrass species have the unusual characteristic of having very biased sex ratios; males make up less than 20% of populations. My dissertation research was conducted on the Olympic penninsula in Washington state with Tatoosh Is. as my primary field site.

I have investigated the consequences of male rarity for the pollination biology of surfgrass (Shelton 2008), developed and applied genetic markers in concert with individual demographic data to determine when during surfgass life-history sex ratios arise (Shelton 2010a), and created a two-sex population model to ask how sex-differences in life-history generate skewed sex ratios and which evolutionary scenarios were most likely responsible for the sex ratio bias observed in nature (Shelton 2010b). I have also manipulated the abundance of surfgrass in tidepools to explore the effect of surfgrass on the temperature regime and community of organisms present in tidepools (Shelton 2010c).

 

 
 

Current Projects

Fish Population Fluctuations

A central, classic question in ecology is what causes populations to fluctuate in abundance. We recently published an article that looks at the effects of fishing on the temporal variability of fish populations. We combined models and available fisheries data to look at the relative support for different hypotheses for the causes of fish population fluctuations (Shelton and Mangel 2011).

Herring

In collaboration with the Alaska Department of Fish and Game (ADF&G), I am using ADFGs excellent time-series of herring abundance and size-at-age data from multiple populations in southeastern Alaska to investigate herring life-histories. To date, I have worked on documenting sex differences in herring growth and maturation and connected such sex differences to their effects on herring stock assessments. Currently I am devising ways to use the these time-series in conjunction with time-series of environmentnal variables (e.g. ocean temperature) to look at the relative effect of density-dependence and environmental conditions on herring growth.

Groundfish

I am collaborating with scientists at NOAA's Southwest Fisheries Science Center in Santa Cruz to develop hierarchical Bayesian models methods to improve estimation of California rockfish landings. We recently submitted a paper on our methods for dealing with missing and sparse landings data to the Canadian Journal of Fisheries and Aquatic Sciences (Shelton et al. in review).

NCEAS working group

I am a member of a working group at the National Center for Ecological Analysis and Synthesis (NCEAS) "Red flags and species endangerment: Meta-analytical development of criteria for assessing extinction risk" organized by Robin Waples and Jeff Hutchings. In collaboration with other working group members, I am leading a project within the working group that aims to combine information from a large number of published stock assessments to examine the effect age structure may have stock-recruitment relationships.

 

 
 

Peer-Reviewed Publications

Shelton, A.O. and M. Mangel. 2011. Fluctuations of fish popualtions and the magnifying effects of fishing. Proceedings of the National Academy of Sciences (USA)

Ma, L., M.L. Stein, M. Wang, A.O. Shelton, C.A. Pfister, and K.J. Wilder. 2010d. A method for unbiased estimation of population abundance along curvy margins. Environmetrics. DOI: 10.1002/env.1053.

Shelton, A.O. 2010c. Environmental and community consequences of foundation species: surfgrass (Phyllospadix spp.) in tidepools. Journal of Experimental Marine Biology and Ecology 391:35-42. (pdf)

Shelton, A.O. 2010b. The ecological and evolutionary drivers of female-biased sex ratios: two-sex models of a perennial seagrass. American Naturalist 175:302–315 (pdf)

Shelton, A.O. 2010a. The origin of female-biased sex ratios in intertidal seagrasses (Phyllospadix spp.) Ecology 91:1380–1390 (pdf)

Shelton, A.O. 2008. Skewed sex ratios, pollen limitation, and reproductive failure in the dioecious seagrass genus Phyllospadix. Ecology 89:3020-3029. (pdf)

Micheli, F., A.O. Shelton, S.M. Bushinsky, A.L.Chiu, K.W. Heiman, C.V. Kappel, M.C. Lynch, and J. Watanabe. 2008. Persistence and recovery of depleted marine invertebrates in marine reserves of central California. Biological Conservation 141:1078-1090.(pdf)

Shelton, A.O., D.A. Woodby, K. Hebert, and J. Witman. 2006. Age determination and spatial patterns of growth of the red sea urchin (Strongylocentrotus franciscanus) in southeast Alaska. Transactions of the American Fisheries Society 135:1670-1680. (pdf)

In review:

Shelton, A.O., E.J. Dick, D. Pearson, S. Ralston, and M. Mangel. Estimating landings and quantifying uncertainty in multi-species fisheries: Hierarchical Bayesian models for stratified sampling protocols with missing data. Canadian Journal of Fisheries and Aquatic Sciences.