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Scientific research methodology applied to aquaponics
The following case studies illustrate some of the different kinds of methodologies that can be used for research relating to aquaponics. The first case study is an example of social science research conducted using a questionnaire. A questionnaire is a tool for collecting and recording information about a particular issue of interest in a standardized manner. The information from questionnaires tends to fall into two broad categories – facts and opinions; very often they include questions about both.
· Aqu@teachRespiration physiology
The air we breathe is mostly nitrogen (78%) and 21% oxygen. The water that fish ‘breathe’ also contains oxygen, but at a much lower concentration, less than 1%. In addition, since water is 840 times denser than air and 60 times more viscous, it takes more effort for fish to ‘breathe’ to extract oxygen, around 10% of their metabolic energy. In comparison, terrestrial animals only use about 2% of their metabolic energy to extract oxygen from air.
· Aqu@teachRecirculating aquaculture system (RAS) technology
A recirculating aquaculture system (RAS) consists of fish tanks and several filtration units which clean the water. In a classic RAS the water is thereby in constant flow from the fish tanks through the filtration system and then back to the fish tanks (Figure 4). Due to the metabolism of the fish, the water that leaves the tanks contains high concentrations of solids, nutrients, and carbon dioxide, whilst it is oxygen-poor compared to inflowing water.
· Aqu@teachProximate composition of fish feeds and essential nutrients
When research began on fish feeds more than 50 years ago, scientists first analysed the natural diets of the species in question. Trout, as an example of a carnivorous fish, had a natural diet that consisted of 50% protein, 15% fat, 8% fibre, and 10% ash, which is high in protein compared to terrestrial mammals. Ever since then researchers have been trying to find the right balance of protein, carbohydrates, fats, fibre, vitamins and minerals for fish used in aquaculture (Bhilave et al.
· Aqu@teachProduction plan and monitoring the evolution of the farm
All aquaponic farms need well defined production goals and a plan to fulfil those goals. Specifically, it is helpful to define the following aspects well in advance: The species to be used The size of fingerlings needed initially and the target size of the adults to be sold at the end. This will help to define the productive cycles on the farm (types of tanks, etc.) The optimal densities and housing conditions for each stage of growth.
· Aqu@teachPrevention methods in integrated pest management
Good plant health is not only the absence of diseases and pests. Good cultivation techniques with adequate nutrition, water quality, climate conditions and production hygiene are required for healthy growth. To achieve sustainable plant protection management, it is essential to understand how to minimize the risk of plant diseases and pests. Prevention is the most important part of integrated pest management (Table 2). Table 2: Plant disease prevention measures in aquaponics
· Aqu@teachPlant selection
This section covers some of the plant species most commonly grown in aquaponic systems. Details are provided on the ideal growing conditions, the length of the growing cycle, common pests and diseases, and recommendations for harvesting and storage. Many varieties of vegetables are available from seed houses. While both field and greenhouse varieties can be grown in a greenhouse, it is advantageous to use greenhouse varieties whenever possible, since they have often been bred to yield very heavily under controlled environmental conditions (Resh 2013).
· Aqu@teachPlant nutrition
Essential nutrient elements Plants require 16 (Resh 2013) or according to other sources 17 (Bittszansky et al. 2016) essential nutrient elements without which they are unable to complete a normal life cycle. Plants require essential nutrients for normal functioning and growth. A plant’s sufficiency range is the range of nutrient amount necessary to meet the plant’s nutritional needs and maximize growth. The width of this range depends on individual plant species and the particular nutrient.
· Aqu@teachPlant anatomy, physiology and growing requirements
Plant anatomy Plant anatomy describes the structure and organization of the cells, tissues and organs of plants in relation to their development and function. Flowering plants are composed of three vegetative organs: (i) roots, which function mainly to provide anchorage, water, and nutrients, and to store sugars and starch; (ii) stems, which provide support; and (iii) leaves, which produce organic substances via photosynthesis. The roots grow down in response to gravity.
· Aqu@teachPlanning the recirculating aquaculture part for an aquaponic system
In aquaponics, it is very important that the input and output of nutrients is in balance over the entire plant growing period. This balance can mainly be controlled using two different approaches: Approach 1: An existing recirculating aquaculture system (RAS) is used to dimension the corresponding hydroponic unit with plants (Figure 12). This approach is covered by the Exercise in Module 5 (nutrient water balance). Approach 2: The RAS is dimensioned based on the desired plant and fish production (Figure 13).
· Aqu@teach