Seasonal nutrition:
I
Matching fish feed to fish physiology by Dr Robert Tillner, Product Manager, Aller Aqua Research, Germany n most areas in the world, nature follows seasonality in one way or another. This affects both physiology and behaviour of animals, across different genera. As many fish species are poikilothermic, their internal temperature varies considerably, as a result of fluctuations in the ambient environmental temperature. In a changing climate, this dependency can have a severe impact on natural and captive fish populations, when rapid drops or rises in environmental temperatures occur, occasionally over a short period of time.
change in water temperature occurs on many fish farms. This is considered the most delicate period in fish farming. The drastic temperature increase affects the metabolism of fish and challenges its immune system. Often, the difficulties fish experience in adjusting to a changing environment become noticeable as poor appetite, apathy and skin lesions. Consequently, fish having problems with changing environmental conditions show reduced growth performance, which results in less profit for farmers. This contrasts with changing farm operations in the transition from winter to spring as feeding intensity increases.
The temperature/metabolism connection
Warming temperatures boost metabolism
The variations in body temperature have a pronounced impact on both the speed and efficiency of fish metabolism. In this respect, fish metabolism is increased in higher temperatures and vice versa. Consequently, the feed intake, as well as nutrient digestibility and nutrient utilisation of fish, vary with temperature. When the seasons change from winter to spring, a rapid
When water temperature rises, fish show a reduced capacity to resorb oxygen from the warmer water, as oxygen solubility in water decreases with rising water temperature. This is especially true for juvenile fish, as they are more susceptible to oxygen deficiencies, compared to adult fish. To cope with these conditions fish, by nature, have a generally
18 | January 2019 - International Aquafeed