Ecasa Toolbox

Shell-fish farming: Optimizing a farm

Optimizing a (bivalve) shell-fish farm means increasing the efficiency with which a site can be used. In most cases optimization requires the best possible growth of the largest possible biomass of harvestable shellfish, with as little deterioration of pelagic or benthic conditions as possible. All animals use oxygen and release ammonia. Where water movements are weak, the build-up of ammonia and the decrease in dissolved oxygen at a farm can adversely effect shellfish growth. In addition, there is little point in stocking more animals than can grow effectively using the available food supply.

Some of the water-column indicators reviewed during ECASA can be used to gain insights into conditions at a farm. Measurements of dissolved oxygen and phytoplankton chlorophyll within the farm can be compared with those outside the farm. If either is substantially lower inside the farm, during the main growing season, it is likely that bivalve production is limited by these factors. In this case, it will be difficult to increase production further at the same site.

The following models can be used to optimize management on the farm scale. They need information on seasonal cycles of temperature and chlorophyll in the water body containing the farm, and on currents at the site. The other organism models studied by ECASA will predict growth as a function of environmental conditions, but need further work before they can be used for site management.

Model (alphabetical order) Model category: scale and relevance Environment category Bivalve type for which applicable Tested at ECASA sites:
DPP Organism/population model microtidal regions of restricted exchange oysters and mussels not tested in ECASA
FARM ShellSIM-like Organism model plus A (farm-scale) transport model all mussels, oysters Creran, Ria Formosa
Longlines organism model plus A (farm-scale) transport model RREs and semi-enclosed coastal waters mussels, scallops not tested in ECASA

 

From the perspective of sustainability, however, optimization should also be addressed at the water-body scale. The estimation of carrying capacity is considered on the page dealing with assessing a site's potential.