Effect of river fragmentation and flow regulation on occurrence of landlocked brown trout in a fish ladder

SLAVÍK, O., BARTOŠ, Luděk a HORKÝ, P. Effect of river fragmentation and flow regulation on occurrence of landlocked brown trout in a fish ladder. Journal of Applied Ichthyology, 2009, 25, 67-72. ISSN 0175-8659.
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Abstrakt

The movement pattern of brown trout in a fish ladder on the heavily fragmented Ohre River, Czech Republic was observed. Some individually-tagged fish repeatedly occurred in the ladder. Repeatedly-caught individuals represented 84.9 % of the total captures. The likelihood of repetitive occurrence decreased with the increase in fish body length. The number of individuals in the ladder was inversely related to temperature, and positively correlated with increasing water flow in the main channel. Fish abundance in the ladder was density-dependent, as the number of individuals was inversely related to fish size and time of residency in the ladder. Spawning migrations were not the best predictor of maximum fish occurrence in the ladder, suggesting that repetitive capture of individuals in the ladder was significantly affected by other factors influencing fish behaviour. Repetitive fish occurrence in ladders can be expected, particularly in rivers with numerous lateral obstructions

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