green-adapted fish. No significant variations were observed in the other parameters. It is concluded that different background colors may lead to different growth performances of
scaled carp depending upon rearing conditions. © 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Background color; Growth; Physiology; Cortisol; Stress; Cyprinus carpio
1. Introduction
It has been shown that in some teleost species a notable background color adaptation occurs as a final result of defense mechanisms Bond, 1996. Color
modification can also occur during fish reproductive period Baker, 1963; Moyle et al., 1996, as well as under stress conditions Mazeaud et al., 1977; Papoutsoglou,
1998. It is well known that these color changes are due to aggregation and dispersion of pigment neural and hormonal process and to alterations in the
amount of pigment and the number of chromatophores hormonal process Bowley et al., 1983; Green and Baker, 1989; Sugimoto, 1993. Hormones involved are
melanocyte-stimulating
hormone a-MSH,
melanin-concentrating hormone
MCH, melatonin, and catecholamines Filadelfi and Castrucci, 1994; Papout- soglou, 1998.
Studies in Oncorhynchus mykiss, Anguilla anguilla, Salmo trutta, Sarotherodon mossambicus, Pleuronectes americanus and Zacco temmincki have shown that
enhanced release of a-MSH is associated with skin darkening dispersion of melanin granules on a black background, whereas high levels of circulating MCH are
related to skin lightening aggregation of melanin granules on a white background Van Eys and Peters, 1981; Iga and Takabatake, 1982; Baker et al., 1985; Pickering
et al., 1986; Powell and Baker, 1988; Burton, 1993. It has also been found that under certain conditions, a-MSH stimulates the secretion of cortisol from interrenal
tissue Lamers et al., 1992, while MCH depresses the release of corticotrophin-re- leasing bioactivity from hypothalamic tissue Baker et al., 1985; Green et al., 1991.
In addition to exhibiting changes in pigmentation, rainbow trout O. mykiss adapted to a black background, in response to externally induced stress, showed
higher plasma corticotrophin and cortisol levels, lower plasma MCH levels and similar plasma a-MSH levels compared to white-adapted counterparts Gilham and
Baker, 1985; Green and Baker, 1991; Green et al., 1991. Also, Baker and Rance 1981, working with O. mykiss and A. anguilla in a noisy aquarium, have shown
that plasma cortisol levels were higher in fish maintained in black tanks for 3 – 4 weeks compared to those in white-adapted counterparts. Furthermore, background
color has been shown to influence the behaviour of Oreochromis niloticus Fanta, 1995.
Although the long-term effects of cortisol on growth rate of fish are well established Pickering, 1993, all the above studies did not pay considerable
attention to the growth performances of teleosts exposed to different background colors and especially to those species with commercial value.
Despite the worldwide economic importance of carp Cyprinus carpio L. culture, which is carried out by the application of all known production systems using
earth ponds, plastic or concrete tanks, net cages, recirculated water systems, there is no published information related to the physiological responses of this species
caused by different rearing background colors.
The present study has been designed to evaluate the effects of long-term adaptation to black, green and white background on growth performances and
physiological responses of scaled carp under certain experimental conditions using a recirculated water system.
2. Materials and methods
