Eels at the Edge: Science, Status, and Conservation Concerns

Eel Population Modeling and its Application to Conservation Management

Giulio A. De Leo, Paco Melià, Marino Gatto, and Alain J. Crivelli


Abstract.—We critically review population dynamics models developed for Anguilla spp. eels. Despite the (quasi) panmictic nature of temperate eel species, most modeling effort has focused on subpopulations within specific brackish or inland water bodies. Models have been developed along three major lines: cohort approaches, input-output models that directly relate juvenile recruit abundance to migrating mature eels, and stage- or size-structured population models, or both, some of which explicitly account for the observed variability of eel life traits. More recently, attempts have been made to extend demographic analyses to the oceanic phase of the eel life cycle. We discuss eel population models in terms of mathematical complexity and usability, amount and quality of data required for calibration, realism in the description of life cycle and demographic parameters, potential for analyzing different fisheries management strategies, and inclusion of environmental and interindividual stochasticity and uncertainty in parameter estimation. While site-specific analyses are needed to understand eel life history in the continental phase, the generalized decline of eel recruitment requires a global assessment of metapopulation viability under different hypotheses and scenarios. Given the high number of unknowns and untested hypotheses, we emphasize the need to explicitly model uncertainty in parameter estimation and environmental and interindividual stochasticity (e.g., by using bootstrap techniques and Monte Carlo simulations). There is an urgent need for population models that can be used for conservation-based eel management in broad geographic areas where few data are available.