Fish Fauna 2013
The present map shows an overview of the current state of knowledge of the fish populations of the Berlin bodies of water through December 2013. After 2003 (02.08 edition 2004), the recording process of the fish population continued consistently in the Berlin waters. Between 2003 and 2013, numerous recording data were updated and new bodies of water, particularly small streams, examined (SenStadtUm 2013a). For the presentation of the current stock situation of the Berlin fish fauna, over 900 catch data from 153 bodies of water were evaluated. The stock-taking is representative, since it contains all major streams and lakes in Berlin, as well as more than fifty of a wide variety of smaller bodies of water. During the recording time period through December 2013, each smaller body of water was fished at least once, and each major one repeatedly, in some cases annually, in some cases at different seasons. All bodies of water were electrically fished. In addition, in the larger bodies of water, fixed nets, fish traps, dragline nets and trawl nets were also used.
By means of the combined use of different types of equipment, the difference in the catch selectivities of the various measurement methods is compensated, which increases the recording precision of the fish population. Particularly in canals and in places with artificial bank reinforcements, the combination of electro-fishing and stationary nets has proven itself; in lake-like river widenings and in areas with unspoiled shore structures, trawl nets are most useful (Doetinchem & Wolter 2003).
The fishing procedure has been carried out according to the usual good practice. Wadable trenches and small bodies of water were fished with a portable DC-powered impulse device, while for larger and deeper bodies of water, a boat with a DC-power unit and partial multi-mesh gillnets are used. The shoreline was sampled with electrofishing device in each case, depending on the breadth of the body of water, the structural variety and the catch success, with the goal of verifying the species spectrum as completely as possible.
Electric fishing is the most efficient of all catch methods, especially for bed substrata such as large rocks, rocky deposits or plant formations. Used correctly, it is also the least disruptive method for recording a fish population, since the fish have the least contact with net material, etc., and thus show hardly any injuries to their scales or mucous membranes. With the aid of a DC-power unit, an electrical field is produced in the water. Fish situated within it receive various voltages, depending on their length and position relative to the lines of force. Depending on the voltage they receive, their reactions range from flight through positive electrotaxis (swimming toward the anode) to electronarcosis. The effective radius of the catch electrode is approx. 2 m, so that pelagic (free-water-living) species and large, shy individuals of all species are under-represented in the catch, due to their greater flight distance. Moreover, the selectivity of electric fishing is altogether far lower than that of other methods, given comparable work and time expenditure.
For the catch evaluation, the species were determined and the individuals counted and measured, and also weighed on a sample basis. Fish larvae and young fish of the same age are for the most part not considered in determining species frequencies, since they have not been included representatively using the chosen fishing methods and the sample size. However, they were registered for species and reproduction verification.