Endocrinological regulation of fish feeding-nutrition under domesticated conditions
by Professor Sofronios E. Papoutsoglou, Agricultural University of Athens, 75 Iera Odos, Athens 11855, Greece.

Abstract

Food identification, acceptance, digestion and assimilation, make up a complicated procedure intending to cover fish demands in energy and nutrients. Physiology of growth and reproduction, tissue biochemical activity and body composition are the results of a combined effect of food intake and neuroendocrine function, regulated by fish genome and depending on environmental factors. The involvement of the nervous system is more obvious in food identification and acceptance (vision, taste, smell), while digestion and assimilation are mainly performed by the endocrine system.

Food availability (quantity and quality) interacting with photoperiod, water characteristics and stress, should be considered as a major factor, in regulation fish metabolic hormones secretion and function. Evidences for hormonal involvement in association with fish food intake, mainly include ACTH and catecholamins, CCK, thyroid hormones, insulin, glucagon, growth hormone and IGFs, expressing their action through several enzyme pathways.

In terms of both food supply (availability and diversity) and water properties, earth ponds could provide (under certain conditions) a rearing environment close to their natural one for several fish species. On the other hand, tanks are more easily associated with the creation of a stressful environment with numerous physiological effects, caused mostly by catabolic hormones, influencing fish nutritional status. However, it must be addressed that in both rearing cases, fish ecological and food ethological demands should be covered by the provision of high living standards, so that they can develop all their physiological activities.

It is obvious therefore that proper fish controlled production has to be the outcome of an intentional rearing management, directed to a continuous existence of proper water quality and fish nutritional status, minimizing stress consequences. The understanding of the importance of food composition in the regulation of endocrine function could provide significant clues not only to manipulate water quality, but also to achieve a successful guide for artificial diets formulation, according to the ethology and nutritional habits of each fish species.