Cormorants Phalacrocorax Carbo in Slovenia: examples from fishponds Race and the Drava river
2000
Vogrin, M. | Vogrin, N. (Hajdina (Slovenia))
Following the population increase in continental cormorants throughout the Europe, numbers of wintering birds in Slovenia also increase. This increase has caused concern among both commercial fishermen and anglers. In this paper we provide general data about cormorants in Slovenia with special emphasis on fishponds Race and the Drava river. In general numbers of cormorants during winter in Slovenia in period 1994-1999 increase (r = 0.86, P 0.05, n 0.05, n = 6) and on the rivers Sava and Krka (rs = 0.46, P 0.05, n = 6). Moreover, on fishponds Race number of cormorants between 1983-1999 increased but not significantly (rs = 0.43, P 0.05, n = 17). For fishponds Race we also calculate how many fishes were eaten by cormorants for particular year and months. Using the bird numbers of each year and month and an individual daily food ration of 560g/day (taken into account also fishes which were injured by Cormorants), the total fish consumption was estimated. The results are presented in Tables 1 and 2. During last six years on the Drava river in average about 1125 cormorants are present during the winter, which means about 7.8 cormorants/km. However we must take into account that cormorants from the Drava river are present also on tributaries. Taking into account all suitable waters along the Drava river (more then 2350ha) this mean less then one cormorants/2ha. According to ringing recoveries cormorants wintering in Slovenia mainly come from Baltic region (e.g. Denmark, Poland and Sweden).
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