Phytochemicals such as alkaloids, flavonoids, pigments, phenolics, terpenoids, steroids and essential oils are a large group of plant-derived compounds commonly found in diets high in fruits, vegetables, beans and cereals. Plant remedies are closely linked to the maintenance of good health in the cultural heritage of many countries. Despite the potential benefits to health and performance as noted in various terrestrial animals, the use of phytochemicals in fish farming has rarely been investigated. Fish culture is under pressure to decrease the use of synthetic antibiotics and chemotherapeutics because of the risk caused to humans by chemical residues in food and by antibiotic resistance being passed on to human pathogens. Consequently, efforts are being made to exploit plants, plant extracts or natural plant compounds as potential alternatives to synthetic chemicals for the stimulation of immune responses and disease resistance in fish. The phytochemicals contained in herbs may enhance the innate immune system and possess antimicrobial capabilities that may be of immense use in fish culture without causing any environmental and ⁄ or hazardous problems. Most phytochemicals are redox active molecules that have anti-oxidant characteristics that may improve the general physiological condition of fish. This review discusses the results emanating from different studies related to the in vivo application of plants and ⁄ or phytochemicals in fish in relation to immunostimulation, antipathogenic and antistress activities. Special emphasis is given to the use of Chinese and Indian herbs as immunostimulants in different finfish species during culture and as antibacterial agents against Aeromonas hydrophila.

There is a constant need to increase productivity in aquaculture, particularly to improve growth rate, feed utilization as well as stress resistance of fish. Because of consumer concerns and strict regulations in many countries, the use of synthetic chemicals, hormones and antibiotics is becoming unviable and natural compounds are more acceptable to the public. A wide variety of chemical compounds are found in plants, and many of them have been shown to have beneficial effects on appetite, growth and the immune status of fish acting through different mechanisms. Phytochemicals contained in herbs may enhance the innate immune system, possess antimicrobial capabilities, and are redox active molecules with antioxidant characteristics that may help to improve the general physiological condition of fish. Many studies have discussed the values of phytochemicals as feed additives. Another paramount concern related to phytochemicals is their endocrine modulator effect that can be applied both in aquaculture targeting the production of table fish and the growing sector of ornamental fish production. Different mechanisms such as the effects at the steroid receptor level, effects on steroid synthesis, distribution and excretion, actions on the hypothalamuspituitary-gonad axis, as well as indirect mechanisms including thyroid and growth hormone disruption have been postulated for the reproductive endocrine disruption in fish populations by phytochemicals. This paper reviews the results of a great number of studies focusing on phytochemicals such as essential oils, saponins, flavonoids and phytosterols discussing their effects on productive traits and the putative mechanism of action.

In this study the predation and ®sh prey selection of otters Lutra lutra L. living by eutrophic ®sh ponds on agricultural land and in a protected area of temperate climate in Hungary were investigated. The correlations between ®sh in the diet of the otters (by spraint analysis involved 1942 and 1280 samples for the two habitats) and the ®sh stock available (by harvest and sample ®shing) were generally close. Prey selection was signi®cantly related to selected species of a particular size range (P < 0.01). The preference calculations were performed with Ivlev's index of preference (E i , minimum 71, maximum +1). Regardless of species, the otters avoided (E i = 70.51) ®sh heavier than 1000 g, with a preference for individuals weighing between 500 and 1000 g (E i = 0.79). No substantial or clear preference was observed in the weight range below 500 g (E i = 70.02±0.38). The preference for ®sh in accordance with their characteristic sites of occurrence within the body of water was also signi®cant (P < 0.01). They avoided ®sh living primarily in open water (E i = 70.64) and to a lesser degree those occurring near the pond bed (E i = 70.22). They favoured ®sh inhabiting the area with a covering of aquatic plants (E i = 0.46), and showed a preference to a lesser degree for ®sh living in the shallow littoral regions (E i = 0.14). With the cessation of ®sh farming and the effect of the drastic changes which occurred in the vegetation, the otters fed substantially on the stock of alternative sources of prey such as amphibians and water insects as well as terrestrial animals, and at such times, depending on season, ®sh became a secondary source of prey.

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. 1999. Feeding habits and trophic niche overlap in a Carnivora community of Hungary. Acta Theriologica 44: 429-442.The seasonal feeding habits of the red fox Vulpes vulpes (Linnaeus, 1758), the stone marten Marłeś foina (Erxleben, 1777), the stoat Mustela erminea Linnaeus, 1758, the badger Meles meles (Linnaeus, 1758) and the otter Lutra lutra (Linnaeus, 1758) were studied in south-west Hungary, in the course of four years. The habitat conditions, because of human influences, were different in the first and second two years. Diet was examined by scat analysis (238, 262, 67, 50 and 1033 samples, respectively). Small mammals, mainly rodents, were the most important prey for foxes, stone martens and stoats in winter and spring. In summer and autumn insects and fruit were added to fox and marten diet, while birds were added to stoat diet. The badger's main food resources were invertebrates (mainly insects) and maize and, in autumn, rodents. Domestic animals (mainly poultry and rabbit) occurred in the diet of the foxes and martens in all seasons, carcasses (mainly Cervidae) in the diet of these predators and in that of the badgers. The predominant prey of otters was fish, but when the abundance of fish declined, the consumption of amphibians increased. Predation on game birds and hare was not significant. In all seasons, niche overlap was high between foxes, martens and stoats. Niche overlap between these species and the badger increased from spring to autumn. Niche overlap between terrestrial predators and the otter was low. The diet of predators were different between the 1st and 2nd periods.

Two, 42‐day feeding experiments were carried out in aquaria working in a recirculation system, to determine the influence of the different dietary fat levels and fat sources on the growth and body composition of pikeperch fingerlings. In the first experiment three levels of dietary fat (F0: 60; F1: 120; F2: 180 g kg−1) were tested, compared with a commercial diet (Trouvit, 240 g kg−1 fat content). F1 and F2 were formulated by adding fish oil. Best growing and feed conversion ratio was obtained with the commercial control diet, which produced also the highest total body fat (117 g kg−1) while respective values of fish fed on the other three diets varied between 74.1 and 85.1 g kg−1. Different feeds had no significant differences in crude protein content of the fish body. In the second test, besides feeds F0, F1 and F2, two additional feeds were formulated containing 127 g kg−1 (L1) and 178 g kg−1 (L2) crude fat (from linseed oil). Dietary fat levels and fat sources had significant effect neither on growth nor on feed conversion ratio. Chemical composition of the whole body did not change significantly due to the different feeds. Linseed oil had a decreasing effect on the sum of saturated fatty acids and increased the oleic and the α‐linoleic acid proportions in fillet. However, total polyunsaturated fatty acid (PUFA) proportion remained constant.

Body color intensity of red-colored koi carp Cyprinus carpio and goldfish Carassius auratus auratus varieties were measured to evaluate the effect of paprika used as a feed additive. Digital photos of the experimental fish were processed and analyzed by using special software. The red, green and blue (RGB) values of images were recorded and grayscale values of R, G and B were analyzed. The RGB values seem to play different roles in the development of the visible 'redness' of the two species. In most cases the B values decreased continuously during the administration of the paprika as a carotenoid feed additive, which seemed to have no effect on this process. The G values remained unchanged or decreased slightly as redness increased due to paprika feeding. The R values had a tendency to increase due to paprika feeding but significant differences can be expected only after 4 weeks at the feeding conditions applied here. Both the initial rate of redness and genetic background are thought to influence the rate of red color intensity change, which was observed to be different in the two fish species studied here.

The present study was aimed to evaluate the efficacy of Basella alba and Tribulus terrestris for induction of masculinisation in Nile tilpia. B. alba leaves and T. terrestris seeds were extracted with water, ethanol, methanol, dichloromethane, hexane and successive methanol and mixed sex juveniles of Nile tilapia were subjected to dietary treatment with the extracts at the concentration of 0.5, 1.0 and 1.5 gm/kg feed. Treatment with both the plants showed no adverse effect on general fish health. There was no significant interaction effects (P>0.05) of solvent and concentration, and solvent and plant material for percentage of males. But, significant interaction effect (P<0.05) of concentration and plant material was observed for percentage of males. Also, there was significant interaction effect (P<0.05) of solvent, concentration and plant material for percentage of males. For dietary administration of B. alba leaves, the highest percentage of males (83.2±0.7) was obtained by treatment with ethanol extract at the concentration of 1.0 gm/kg feed. For all the solvents, the highest percentage of males was observed at the concentration of 1.0 gm/kg. But, in treatment with T. terrestris seeds, the highest percentage of males (88.9±1.1) was obtained with ethanol extract at the concentration of 1.5 gm/kg feed, which was also the highest percentage of males for all the treatment categories.