Pelagic (water quality) indicators

Introduction

Water quality indicators i.e. chlorophyll content, nutrient concentration, oxygen concentration, transparency of the water column (Secchi depth), and the concentration of particulate organic matter, POC, can be used to evaluate the effect of aquaculture on the surrounding environment. The values of these indicators can be found by in-situ observations. Other indicators can be used to evaluate how the water quality of the surrounding water influences the actual farm. Examples of such indicators are holding capacity expressed as maximum production with respect to oxygen and ammonium conditions in the farm, and fish growth. These indicators are calculated, and do not only depend on one parameter e.g. oxygen or ammonium concentrations of the surrounding water but also on the flushing time, temperature, fish species etc.

The assessment document elucidates among other things the fact that most of the indicators mentioned above describe the instantaneous condition and do therefore show large variations over time. Long (years) and rather frequent measurements are needed to find trends or changes in the environment. The objective of the document was to assess the different water quality indicators suggested during ECASA based on some important evaluation criteria, i.e. obvious significance, clarity in design, realistic collection or development costs, availability of data, high quality and reliability, theoretical basis, appropriate spatial and temporal scale.

To view an assessement of these water quality indicators, click here (PDF).