research

Current projects

Biphasic Growth Modeling: The biphasic growth model (Lester et al. 2004, Proc B, 271:1625) is an exciting alternative to the von Bertalanffy growth model that explicitly accounts for the changes in growth that occur at maturity, and allows for inferences about life history traits and their constraints that would otherwise be impossible. I am using the biphasic model as part of Compensation Modeling (Lester et al. in press), to estimate the mortality rate of 26 shark species (Moe and Venturelli, in final prep) and to assess fisheries-induced evolution in a model species (in prep).

Coastal wetland restorartion: I am part of a large, interdisciplinary team that is developing quantitative models to predict how physical, chemical and biological processes interact to affect the dynamics of coastal river deltas. We will use this information to propose and evaluate restoration efforts aimed at buffering Louisiana’s coast against climate change-induced storms and sea level rise. My job is to predict fish productivity in space and time by modifying the spatially-explicit, individual-based food web model that I developed during my post-doc (watch here), and coupling this model to sediment transport and vegetation models that are in development.

Compensation Modeling: My collaborators and I have developed an exciting new approach for predicting sustainable exploitation rates from compensatory changes in growth (and to a lesser extent survival). We describe and demonstrate this approach in a new paper (Lester et al. in press). Compensation modeling combines life history theory, biphasic growth modeling and temperature-dependency, and is therefore applicable to any species for which we can estimate growth compensation and basic life history. The analytical model requires that capture length be ≤ length-at-maturity, but I am developing code to handle any harvest scenario.

Degree-days: The degree-day is an index of thermal energy that is underutilized in fish science, despite its ability to explain and predict growth and development. Degree-days permeate much of my work because they are often a better alternative to calendar time (i.e., age). It is my goal to increase the (appropriate) use of degree-days in fisheries science. For example, by arguing for standardized base/threshold temperatures (Chezik et al. in press), and developing degree-day models for predicting egg hatch date when temperature is variable (two papers in prep).

Invasive Species: My PhD student, Grace Loppnow, is exploring induced nest failure as a way to control invasive bass (Loppnow et al. 2013). This project combines modeling with small-lake experiments and a large-lake collaboration with the Minnesota DNR and a state angling group. I am also part of the newly-minted Minnesota Aquatic Invasive Species Research Center. When funding is in place, I will develop population models to direct control efforts and evaluate control options/scenarios (see a poster).

Maternal Influences & Age Truncation: Part of my PhD research showed that maternal influences can shape the dynamics and sustainability of stocks subject to strong age- and size-selective fishing (Venturelli et al. 2009, Venturelli et al. 2010). These results are at odds with most fisheries management, have implications for our understanding of stock declines, and invite policies that protect rather than target reproductively valuable individuals. To this end I have reviewed the ability of freshwater fishing regulations and Canada and the US to protect age structure (in prep). I am also shopping around for help in exploring the economic consequences of a “throw the big ones back” policy. Last year, I joined the Age Truncation Effects group, an international team of young researchers who are building a worldwide fisheries database and examining the effects of age-truncation (and climate) on stock variability (e.g., Hiddink et al. in review).

Spawning Habitat: As part of a large effort funded by the International Joint Commission, my MSc student, Jason Papenfuss, is combining field data and modeling in GIS to determine how walleye (Sander vitreus) spawning habitat is affected by the rule curve that governs water levels in the Namakan Reservoir.

past projects

Recovery Modeling: In collaboration with Fisheries and Oceans Canada, I recently conducted recovery potential assessments for the endangered pugnose shiner (Notropis anogenus [Venturelli et al. 2010a]) and the threatened channel darter (Percina copelandi [Venturelli et al. 2010b]). For this work, I used available life history data to develop a matrix (life cycle) model. I then used this model estimate (i) the sensitivity of population growth rate to perturbations, (ii) minimum viable population size and minimum habitat requirements, (iii) allowable harm, and (iv) long-term projections of population recovery under a variety of feasible recovery strategies.

Food Web Dynamics in a 'Novel' System: The ecology of invertivorous northern pike (Esox lucius) is poorly understood. For my Masters research, I conducted whole-lake and mesocosm experiments to determine the effect of (a) an introduction of pike into a small, fishless, boreal lake on their macroinvertebrate prey [Venturelli & Tonn 2005]; and (b) a macroinvertebrate diet on the growth of pike. Results suggest that predation by pike on leeches and other large invertebrates structures communities of littoral macroinvertebrates, and that such a diet compromises the growth of adult pike, but not juveniles [Venturelli & Tonn 2006].

prospective students

I do not have funding to take on another student at this time. If you have your own funding or your GPA and GREs are very competative, then please send me your CV and a brief description of your research interests.