Generalized Predatory Impact Model: A Numerical Approach for Assessing Trophic Limits to Hatchery Releases and Controlling Related Ecological Risks

Abstract

Rigorous assessment of species and ecosystem biology underpins responsible marine stock enhancement. Estimation of limits to stocking density, based on ecosystem productivity and energetic requirements of stocked species, can be used to gauge the appropriate magnitude of release densities, minimizing waste of resources, and the possibility for adverse stocking effects. A generalized mass-balance model (generalized predatory impact model) for stocking density estimation has been developed. The approach is based around the principles of ECOPATH and accounts for dynamic estimation of stocking-related ecosystem relationships at fine temporal (days) and spatial scales. The main parameter inputs include probability distributions for key biological and life-history traits of stocked species and estimates of primary productivity for the target ecosystem. The energetic requirements of stocked fish are evaluated in terms of growth and mortality as well as ontogenetic transitions in diet, habitat use, morphology, and migration. The theoretical carrying capacity for a stocked species within a given arena is assessed from primary productivity, levels of predation by stocked fish on different trophic groups, and a specified level of acceptable trophic impact. A Monte Carlo analysis of uncertainty is used to provide a probability distribution of stocking densities for a given trophic impact. The model is applied for stocking juveniles of snook (Centropomus undecimalis) in Sarasota, FL, USA, and mulloway (Argyrosomus japonicus) in Georges River, NSW, Australia. The model is useful for estimating an appropriate stocking density when planning pilot-scale fish releases. Such releases should be carefully monitored to validate model assumptions and determine density-dependent and other environmental effects.

Improving consumption rate estimates by incorporating wild activity into a bioenergetics model

“…The variance, or uncertainty, of parameter values was incorporated into final consumption rate estimates for each of the three models using Monte Carlo simulations in MATLAB (Mathworks Natick, Massachusetts, USA; Taylor et al. ). Consumption rate simulations accounted for the uncertainty in parameter estimates by sampling parameter values from normal probability distributions.…”

“…A multiple linear regression of standardized simulation results was used to express consumption as a function of parameter values, and the resulting parameter coefficients represent the relative importance of parameters in determining consumption rates (Smith et al 2012). The variance, or uncertainty, of parameter values was incorporated into final consumption rate estimates for each of the three models using Monte Carlo simulations in MATLAB (Mathworks Natick, Massachusetts, USA; Taylor et al 2013a). Consumption rate simulations accounted for the uncertainty in parameter estimates by sampling parameter values from normal probability distributions.…”

“…Consumption is the essential element of trophic ecology, from single‐species models to ecosystem models (Kinzey and Punt ; Taylor et al. ). Such models will be improved when the activity component of individual consumption is derived from field data, under local conditions and for specific species, and incorporates the real variation in wild activity.…”

“…Despite the recent advances in technology that can help predict metabolic rate, few studies have linked metabolism and activity rates of free-ranging animals with estimates of consumption or predatory impact (e.g., Halsey et al 2008a;Payne et al 2011). Consumption is the essential element of trophic ecology, from single-species models to ecosystem models (Kinzey and Punt 2009;Taylor et al 2013a). Such models will be improved when the activity component of individual consumption is derived from field data, under local conditions and for specific species, and incorporates the real variation in wild activity.…”

Evolving Context and Maturing Science: Aquaculture-Based Enhancement and Restoration Enter the Marine Fisheries Management Toolbox

“…Taylor et al (2013a) present a food consumption model for stocked populations to assess trophic limits to stocking density and related ecological impacts. Such trophic models pro-vide an important complement to population models already available for assessing enhancement programs.…”