The corticotropin-releasing factor system as a mediator of the appetite-suppressing effects of stress in fish.

A growth response study was carried out to evaluate the influence of artificially submerged macrophytes on growth performance and supplemental feed utilization of Nile tilapia, Oreochromis niloticus (L.) fry under aquarium conditions. In glass aquarium (80 x 50 x 50 cm) filled with 140 litres of well-aerated tap water (25 to 28 o C), leafless stems of phragmites plant (0.7 m long and 0.5 cm diameter) were used at densities of 0, 25, 50, 75, 100 and 125 stems/m 2 . The final fish weight, weight gain and specific growth rate (SGR) decreased significantly with the increase in plant density (P 0.05). The total lipid content was only decreased, while ash content increased significantly at plant density of 125 stems/m 2 . It could be recommended that submerged macrophytes, used as fish refuges from predators or for periphyton production, should be at low or moderate density, however, dense vegetation reduces significantly fish growth and feed utilization.

The effect of Artificial Vegetation Density on Growth and Growth related Parameters of Nile Tilapia, Oreochromis niloticus (L.) Fry

This research thesis was supported by Nutreco Aquaculture Research centre / Marine Harvest (Stavenger, Norway) and the University of Stirling, as well as the Fisheries Society of the British Isles for providing a small research grant towards the cost of the hormone analysis. 

by Nutreco Aquaculture Research Centre / Marine Harvest and University of Stirling

/pdf/environmental-influences-on-the-physiological-and-16iv9aqv8r.pdf

Environmental influences on the physiological and behavioural growth responses in salmonids; with reference to the growth-dip phenomenon

Nonlinear time series analysis of food intake in the dab and the rainbow trout

Our understanding of the timing of stress responses and specific roles of different regulatory pathways that drive stress responses is incomplete. In particular, the regulation of appetite genes as a consequence of exposure to different stressors has not been studied in sufficient detail in fish. Therefore, a stress trial was conducted with koi carp, aiming at identifying typical effects of stress on regulation of appetite genes. The stressors tank manipulation, air exposure and feed rewarding were chosen. The responses to these stressors were evaluated 10, 30 and 60 min after the stressors were applied. Orexigenic and anorexigenic genes were investigated in four different brain regions (telencephalon, hypothalamus, optic tectum and rhombencephalon). The results show that, apart from the typical appetite regulation in the hypothalamus, the different brain regions also display pronounced responses of appetite genes to the different stressors. In addition, several genes in the serotonergic, dopaminergic and gaba-related pathways were investigated. These genes revealed that rearing in pairs of two and opening of the tank lid affected anorexigenic genes, such as cart and cck, which were not changed by air exposure or feed rewarding. Moreover, distress and eustress led to limited, but distinguishable gene expression pattern changes in the investigated brain regions.

T Lyytikäinen

Papers

The acute effect of cortisol implant on self‐feeding activity of rainbow trout Oncorhynchus mykiss (Walbaum)