Resumen de Modelling estuarine stocking density for crustaceans using net ecosystem metabolism
Matthew D Taylor, James A. Smith, B. D. Eyre
Stocking is increasingly used as a tool for fishery enhancement in estuarine environments. Stocking densities are often estimated by modelling resource availability, but this can be difficult for lower trophic level species, such as crustaceans, which can consume a wide variety of difficult-to-sample food resources. We present a stocking model that uses net ecosystem metabolism (NEM) as the basis for a production-based stocking model, which simulates maximum stocking density by balancing NEM with consumption by the stocked organism. In a case study of a stocked prawn in an estuary, stocking density was large at approximately 11 million prawns (in 4 km2), with a 95% confidence interval of 4.3–32.4 million. This was due to high NEM, low prawn trophic level (2.2), lake-wide habitat suitability, and was based on dedicating 1% of the benthic primary production to stocked prawns. Prawn consumption peaked 6–8 wk after stocking, and prawn biomass peaked 14–16 wk after stocking (approximately 16 t). Our simulation showed that food limitation is a determining factor for cohorts with fast growth, but as growth slowed, other density-dependent factors (namely space limitation) influenced stocking density. A sensitivity analysis confirmed the importance of growth rate on stocking density; thus, accurate measures of growth and its temperature-dependence should be a priority for stocked species. Using NEM as a basis for resource limitation by stocked consumers allows the temporal dynamics of both primary production and consumption to be incorporated, and is a powerful approach for calculating stocking densities for low trophic level consumers with diverse diets, such as prawns, shrimps, and crabs.
