Feeding and Metabolic Rate

                                

Feeding - The act of consuming food is called feeding. The feeding of fish and their nutrition is one of the most important factors in keeping them healthy. Since fish are very diverse in their habits, there is a large diversity in their eating patterns too. Some fish, for instance, are bottom feeders, while others are mid-water feeders or surface feeders. Some fish species will even jump out of the water to catch insects! You will also notice that some fish enjoy eating your plants while others enjoy eating your other fish. Obviously, a single type of food will not be enough to meet the requirements of the fish. That is why many of the exotic varieties of fish shouldn’t be maintained in an aquarium by anyone but an experienced aquarist. Their native food and the varieties that they need to survive and do well are to though for less experienced aquarists to provide. Most of the fish that have adapted to aquarium life can be trained and habituated to eat different kinds of food. The first step is that the fish has to be able to recognize food. Even the most nutritious of food goes to waste if the fish does not understand that it is to be eaten. Both instinct as well as training affects this recognition. Hunger is not the only thing that leads a fish to food. Security as well as good health is also necessary.Upon introduction into its new home, a fish may not take to its food right away. If your aquarium does not resemble its natural habitat or is completely devoid of friendly objects like plants, the fish may feel insecure. Sometimes, the temperature in your aquarium is just not right, or the intensity of the glare coming from your lights can be too harsh. Dimming lights a bit until the fish get used to the lights is a good idea

 Feeding:

The food energy requirements of fish are only about ten percent of what is necessary for mammals and birds (Smith, 1989). This is due in part to the fact that fish are exothermic (cold blooded) so they do not expend energy for maintaining body temperature.
Feeding behaviors:

• Appetite
• Visual and chemosensory ability
• Restricted area searching
• Responding to and capturing prey
• Handling and ingestion of food

Fish rely on their sensory abilities for cues that alert them to the availability of foods. These sensory abilities include olfactory (taste and smell), hearing and visual cues. Stress can inhibit these sensory abilities and it has been observed to disrupt any or all of the components of feeding behaviors (Beitinger, 1990). Stress can also cause digestive processes to cease temporarily."(Mazeaud & Mazeaud 1981).
Fish normally search areas within their territory or aquarium where they feel safe and have found food before. Stressed or sick fish can have a reduced appetite and simply are not hungry despite the need for nutrition. Toxins or other forms of stress can impair the ability of fish to taste, smell or visually recognize foods. Stress can inhibit the response to prey (or other food) and the ability of fish, including swimming ability, to capture prey. Have you have ever seen a fish take food into their mouth only to spit it out again? This is an example of not properly handling or ingesting food. This fish may or may not have an appetite, it did taste, smell or visually recognize the food, it probably was searching, it responded to and captured the food, yet it did not handle or ingest the food properly.
Fish tend to recover feeding activities when they regain normal homeostasis or equilibrium. The timeframe it takes fish to recover feeding behaviors depends on the severity of the stress and the physiological state of the fish. There is a correlation between the resumption of feeding behaviors and the re-establishment of normal physiological status (homeostasis). When cortisol (stress hormone) in the blood returns to a pre-stress level the fish usually begin to eat again.
Stress and high temperature increase oxygen consumption. Digestion also requires oxygen and energy. Increased oxygen consumption during digestion is referred to as a phenomenon called "Specific Dynamic Action" or SDA (Yu, 2004). It is a good idea to withhold feeding or at least to reduce the amount of food offered when the water temperature is high, because the oxygen demand could exceed the supply (Stevenson, 1987).
Factors influencing feeding behaviors:

• Overall health
• Security
• Temperature
• Photo-period
• Osmoregulatory balance