# Aquasafe: A Remote Sensing, Web-Based Platform for the Support of Precision Fish Farming
## 2 Materials and Methods
### Indicators  
Based on the parameters that have been identified as affecting the survival and growth of the farmed species, we have developed five indicators that can be used as warning signs, along with appropriate thresholds (Figure 1c). The five indicators are: (i) the concentration of algae (algal blooms), (ii) sea surface temperature, (iii) the saturation of dissolved oxygen, (iv) the fish growth, and (v) the wind speed and gusts. By setting appropriate thresholds for these indicators, the system will alert the administrator or the operator of the farm of potential threats and required actions. 1. [label=()]
2. Algal blooms: Most marine aquaculture facilities consist of bivalve molluss, finfish, and crustaceans and are placed in estuarine or coastal locations [37]. Such areas are more vulnerable to eutrophication risk due to the large supply of nutrients, mainly phosphorus and nitrogen, caused by human activities (i.e., sewage systems, industrial waste, agricultural activities, etc.). These conditions combined with unusually high water temperature, extreme weather events, and low water circulation can lead to the overgrowth of microalgae (algal blooms), which can range from mild to very intense [38]. The overgrowth of algae blocks sunlight to the lower layers of water bodies and can lead to oxygen depletion, causing critical conditions for the survival of aquatic organisms. Some types of algae blooms also produce toxins, which can be harmful to human health and aquatic life [37; 38]. The appropriate threshold for chlorophyll-a to avoid algal blooms can vary depending on the specific body of water and its intended use. An initial threshold of 10 micrograms per liter was selected as the default value, though the user is able to manually adjust this parameter to suit the specific circumstances. 2. Sea Surface Temperature: The sea surface temperature (SST) plays a crucial role in the survival and growth of armed fish. Different species have different optimal temperature ranges for growth and survival. For example, gilthead seabream and European seabas are able to tolerate a wide range of SSTs ranging from 5 to 34 \({}^{\circ}\)C and 2 to 35 \({}^{\circ}\)C accordingly [39], but their optimal temperature ranges vary depending both on the species and the growth stage. Gilthead seabream thrives in temperatures between 18 and 28 \({}^{\circ}\)C, European seabas between 17 and 24 \({}^{\circ}\)C [40,41]. They may be able to survive in a wider range of temperatures; however, prolonged exposure to temperatures outside of these optimal ranges can negatively affect the growth and survival of these species. High temperatures can lead to decreased growth rates and increased susceptibility to disease, while low temperatures can lead to reduced feed intake and metabolism [39]. Therefore, it is important to ensure that the SST in aquaculture facilities stays within the appropriate thresholds to ensure the well-being of the armed species. 3. Dissolved Oxygen Saturation: Dissolved oxygen is a key indicator that affects the survival and well-being of all aquatic organisms and is measured in mg/L [42,43]. The solubility of oxygen in water is affected by the temperature and salinity of the water, and oxygen levels are typically expressed as the percentage of oxygen that can be dissolved in the water at those conditions compared to the maximum (saturation). Saturation levels at a particular level of temperature and dissolved oxygen can be obtained from solubility tables or calculators ([[https://www.engineingtoolbox.com/oxygen-solubility-water-d_841.html](https://www.engineingtoolbox.com/oxygen-solubility-water-d_841.html)]([https://www.engineingtoolbox.com/oxygen-solubility-water-d_841.html](https://www.engineingtoolbox.com/oxygen-solubility-water-d_841.html)) (accessed on 20 April 2023)), and it is critical for the respiration and growth of fish. In order to ensure suitable conditions for armed fish, it is important to maintain appropriate levels of dissolved oxygen saturation.