Many behavioural patterns or reactions in fish seem to be energetically determined or at least linked. In previous experiments on behavioural thermoregulation [3,5], decreased motility during starvation periods [2] and changed behavioural patterns in chemical stress situations [1] were repeatedly observed and theoretically explained by energetic mechanisms. Especially larvae and juveniles normally forage with a strongly limited metabolic scope. To get additional physiological information further to our previous and continuing behavioural investigations in fish, we decided to design equipment for the joint registration of motility parameters and oxygen consumption of small fish, fish larvae and daphnia in a single aquarium system. The device consists of a small observation unit (whereas different aquarium sizes are possible) with a constant water flow and a recirculation (cleaning, heating and aeration) system. The animals can be fed during the experiments, so experimental periods from days to some weeks are possible. The behavioural parameters motility, turnings, swimming height, horizontal distribution and individual distances are registered and calculated by the video recognition system BehavioQuant® (first presented at Measuring Behavior '96 [4]. A controlling unit driven by a second program simultaneously running on the computer regulates the temperatures and measures the oxygen content of inlet and outlet water of the fish chamber. Time intervals between measuring in and out values are destined by the flow-through time of water. The instantaneous temperature and oxygen values as well as the movement of registered objects can be observed on screen without disturbing the animals. Registered data are transferred to a desktop computer where recalculation and evaluation goes on.

In our first experiments with carp juveniles we got a strong correlation between motility and oxygen consumption as well as some influences of chemical stressors. A subsequent analysis of fish body composition (proteins, lipids and carbohydrates) and detoxification enzymes before and after the experiments will give us some more information about the metabolic pathways of dissipated energy.

References

1. Baganz, D.; Staaks, G.; Steinberg, C. (1998). Impact of the cyanobacteria toxin, microcystin_LR on behavior of zebrafish, Danio rerio. Water Research, 32, 948-952.
2. Hardewig, I.; Staaks, G.; van Dijk, P. (2000). Interactions between temperature preference and nutritional status in fish. Poster, Annual Meeting of the Society of Experimental Biology, Exeter, UK.
3. Krause, J.; Staaks, G.; Mehner, T. (1998). Habitat choice in shoals of roach (Rutilus rutilus) as a function of water temperature and feeding rate. Journal of Fish Biology, 53, 377-386.
4. Spieser, O.H.; Scholz, W. (1992). Verfahren zur quantitativen Bewegungs-analyse von mehreren Objekten im selben Medium. (A Method of Quantitative Movement Analysis of Multiple Objects in the Same Medium.) German Patent P 4224750.0.
5. Staaks G. (1996). Experimental studies on temperature preference behaviour of juvenile cyprinids. Limnologica, 26, 165-177.

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