FISH ANATOMY, HEALTH, AND WELFARE
Respiration 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@teachGeneral internal anatomy
In this section we will outline the most important internal organs of fish (Figure 4), underlining the main differences with mammals and some important facts that influence how fish should be maintained. Figure 4: General internal fish anatomy (source http://www.animalsworlds.com/internal-anatomy.html) Brain Fish have small brains compared to terrestrial vertebrates. For example, the human brain weighs approximately 1.4 kg and represents around 2% of the total body mass, but fish brains only represent 0.
· Aqu@teachGeneral external anatomy
The main idea of this section is to introduce several important anatomical features of fish and to relate them to function and physiology. There are more than 20,000 species of freshwater and marine fish on our planet, each with specific requirements and ecological niches, which has led to specific body adaptations. However, many of the fish, especially teleosts (bony fish with a moveable pre-maxilla), share some common features. Although the number of species used in aquaculture is probably over 200, the number used in aquaponics is narrower, and mostly restricted to freshwater fish (Table 1).
· Aqu@teachFish welfare
Introduction Aquaculture is one of the few types of animal farming that has grown continuously over recent decades, by about 10% annually on an international level (Moffitt & Cajas-Cano 2014). However, as production increases and new methods appear, such as aquaponics, we have been witness to more problems related with fish health and welfare. Although it may seem surprising, more than 1300 scientific articles have been published on fish welfare since 1990 (see Table 2).
· Aqu@teach