CHARACTERISTICS OF BROWN TROUT (SALMO TRUTTA M. FARIO L.) REDDS IN SELECTED STREAMS OF THE RUDAWA RIVER BASIN
Tomasz Mikołajczyk, Grzegorz Witkowski, Rafał Gawlyta, Krystian Tyrcha, Sławomir Mrożkiewicz, Mirosława Sokołowska-Mikołajczyk, Piotr Epler
Deptartament of Ichthyobiology and Fisheries, Agricultural University, Cracow, Poland
ABSTRACT. The quantity and characteristics of brown trout redds located in four streams of the Rudawa River basin in the Cracow Valleys Park (Park Dolinki Krakowskie) were investigated. The study was performed in late fall 2001 in the Będkówka, Kluczwoda, Racławka and Rudawka streams, all of which are left bank tributaries of the Rudawa River. A total of 328 redds were noted. The characteristics of twelve redds from each stream were described in detail, including water depth above the dome, water speed above the dome and the surface area of the redd. The contribution of certain gravel sizes in the composition of the domes was also investigated. There were no differences among the streams with reference to the surface areas of the redds or the water speed above the domes. The surface area of the redds ranged from 2081 to 3044 cm2, while water speed above the dome varied from 73 to 82 cm s-1. Significant differences in the water depth above the dome were noted among the different streams (from 12.58 cm in the Kluczwoda to 33.62 in the Rudawka). The contribution of fine gravel fraction (= 1 mm) also varied significantly among the streams. The highest sediment content was recorded in the Rudawka and Kluczwoda streams at 14.22 and 13.28% of the total weight of the gravel sample, respectively. This indicates that, despite the large number of redds in these watercourses, the final results of spawning could be very poor because of the probability of the asphyxiation of embryos by sediments. The Będkówka Stream is the most productive and promising trout spawning ground in the whole basin, and, as such, should be put under special protection.
Key words: BROWN TROUT REDDS, NATURAL SPAWNING
Tomasz Mikołajczyk, Akademia Rolnicza, Katedra Ichtiobiologii i Rybactwa, ul. Prof. T. Spiczakowa 6, 30-199 Kraków-Mydlniki; Tel./Fax: +48 12 6375176; e-mail:email@example.com