Environmental Engineering Reference
In-Depth Information
2. General aspects of applied ecophysiology
The physiological ecologist seeks to understand the organism in relation to its environment.
Defining the environment in aquaculture is relatively easy because it is, in many cases, a
relatively closed system with the exception of marine cages or extensive culture. Three basic
concepts are involved in applied ecophysiology (1) perception, (2) distribution on the
culture environment and (3) the environment. Different animals perceive their surroundings
in different ways, and to some extent, physiological and behavioural
responses are
dependent on perception. There is always a danger that we will superimpose our own
human perceptions on other species and environments. Aquaculture is plenty of procedures
that farmers have been translated from agriculture to aquaculture with not always success
and in so doing fail to appreciate the interaction between organism and culture
environment. The aquatic environment is completely different from the terrestrial
environment and thus the perception of animals is so different from that we have. Water is
more dense than the terrestrial environment provoking that organisms have developed a
series of adaptations to perceive smells, spaces and physical and chemical conditions
completely different from those of terrestrial animals.
Distribution on the culture environment take into account that individuals have limited
tolerance ranges of temperature, salinity and other physical and chemical factors. Thus, is a
truism that populations of organisms not be found in abundance beyond the tolerance
regions of most individuals. Physiological tolerance and functional morphology go a long
distance toward predicting where a particular organism will not occur, but they often give
little indication of how well or what the organism will be doing, whether it will occur at all,
within its tolerance limits. Applied to aquaculture, ecophysiology tries to establish the
tolerance and resistance of species to environmental variables in order to provide the best
culture conditions and how must be the environment to obtain the maximum scope for
growth. Aquaculture environment is one of the topics of applied ecophysiology because the
structure of the environment, interaction between individuals, water chemical and physical
characteristics, type of food, etc., affect the physiology of aquatic animals enhancing or
limiting animal performance, and at the end the biomass production. In this context, seed
density, behavior characteristics that enhance or reduce cannibalism, turbidity, ecological
characteristics of the culture systems that include meio-fauna and vegetation, are analyzed.
A physiological response represents the sum of all cellular and biochemical reactions as
influenced by the environment or the animal itself. For this reason, organisms are capable of
reflecting any environment condition even before the effects are observed in the population
and community level. In ecological energetics an energy budget equation is defined as the
sum of the energy from food ingested, which is divided into metabolizable, egested and
excreted energy. This energy will varied according to the effects of different extrinsic and
intrinsic factors and therefore it is important to calculate the cost of production in terms of
growth when considering total aquaculture activity. Thus, the animal production (P) or
growth is represented by the difference between the absorbed energy and the energy lost in
respiration and excretion, taking age, sex, and body type into account. As with growth,
other measures of biological productivity, such as work, egg production and body
condition, will also affected by type of food or/and environmental characteristics. Thus, a
satisfactory diet/environment in terms of the best efficiency will be needed in order to
achieve optimal animal production.
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