Effects of different culture systems on growth, immune status, and other physiological parameters of tench (Tinca tinca)

Abstract

Tench production is limited in traditional and low intensity cultures. However, its demand is increasing and makes necessary the evaluation of physiological parameters that could affect tench welfare under intensive conditions. This study analyses the growth performance and related indices, hematological and immunological parameters as well as hormone profile and electrolytes in plasma, in fish under three different culture systems: extensive (E), with initial density of 0.07kg/m3, no control of environmental parameters and natural feeding; semi-intensive (SI), with initial density of 0.42kg/m3, partial control of temperature and supplementation of artificial food; and intensive (I), with initial density of 2.5kg/m3, total control of photo- and thermo-period and exclusive artificial diet. Results showed that variables such as weight, length, density increase and specific growth rate (SGR) were higher in I. Higher hepatosomatic index were found in I and SI. In addition, E and SI cultures, which kept natural conditions, achieved greater gonadal increase in detriment of somatic growth. On the other hand, the analysis of hormones and electrolytes, hematological and immunological parameters did not reveal a disturbed immune function in I compared to SI and E. Thus, the general activation of the nonspecific immune system and the mobilization of energy reserves associated to gonadal maturation in fishes from S-I and E systems could be related to an adaptive, non-pathological, response to the natural environmental changes, resulting in reduction of productivity. With all in mind, it can be concluded that adequate artificial feeding and control of the environmental parameters can improve tench productivity by intensive systems without major perturbations of its welfare.