Reaction of fish larvae to the water of the River Elbe at Hamburg harbour

The River Elbe is one of the biggest streams carrying pollutants of all kinds into the North Sea. However, investigations of direct effects of the Elbe water on river life are not numerous. Early life stages of common whitefish and carp were reared under comparable conditions in water of the River Elbe, and in tap water, respectively. No direct effects on the viability of the fry could be found by observing mortality and growth rates in both treatments. Whitefish larvae were severely infested by parasitic ciliates which were able to build up a dense population in the river water. In these experiments life conditions for the protozoa seemed to be much better than in tap water. Mortality rates of early larvae of common whitefish were lower in the Elbe water than in tap water. Mortality, growth rate and starvation resistance of carp fry was equal in river and tap water.