Page 50 - fish_farms_curriculum

5.6. Water Temperature

Temperature has a key influence on the physiological processes of fish. Each fish species is

known to have a species-specific temperature index for survival and growth. Maximum
growth is achieved at optimal temperatures within this thermal tolerance range. With the

increase in temperature, the food intake also increases towards the maximum, and then a
decrease is seen in this increase as the thermal upper limit is reached. Usually, maximum feed

intake occurs a few degrees above the specified optimal water temperature for growth. The

metabolic rate increases exponentially with increasing temperature, and the difference
between feed intake and metabolic rate at any given temperature determines the energy

available for growth. These parameters are indeed very important for cultivated species. In
other words, temperature is very important in maximizing the efficiency in converting the

received nutrients into growth.

Temperature affects all vital activities of fish as well as all living organisms. Many important
activities, from ovarian development to egg development, from immune system to body

weight gain, take place under the influence of water temperature. The importance of

temperature in terms of aquaculture can only be better understood after understanding its
biological importance. The optimum temperature range determined for egg development is

almost the first steps to success in fry rearing. Determining the optimal water temperature and
monitoring the live weight gain of the fish are among the most important concepts considered

in the preparation of feeding protocols. Food intake and digestive physiology under the
thermal effect are the most interesting subjects in the field of cultivation. The most important

arguments in the breeding race are the conditions and protocols under which conditions and

protocols can be forced to achieve the highest level of performance, as well as the species
characteristics of the grown species.

Fish and crustaceans are “poikilothermic” or cold-blooded creatures. This means: the body

temperature of such creatures is roughly the same as the temperature of the water they are in.
For this reason, when the water temperature of fish or crustaceans changes, their body

temperature also changes frequently. All biochemical processes are temperature dependent. It
is so dependent that every 10ºC increase in temperature roughly doubles the rate of

biochemical processing, depending on the species and its habitat.

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