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

O. Slavík, L. Bartoš, P. Horký
2009 Journal of Applied Ichthyology  
The movement pattern of brown trout Salmo trutta (L.) in a fish ladder on the heavily fragmented Ohrˇe River, Czech Republic was observed for 16 months. Some individuallytagged fish repeatedly occurred in the ladder. A total of 1640 fish represented captures of 595 S. trutta in the fish ladder; 247 fish were caught once and 348 individuals were caught repeatedly. Repeatedly-caught (348) individuals represented 1393 (84.9%) of the 1640 captures. The likelihood of repetitive occurrence decreased
more » ... ith 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. Habitat measurements Water temperature (°C, microprocessor Oxi 196 -WTW), concentration of dissolved oxygen (DO, mg L )1 ) and flow (m 3 s )1 , officially measured profile by the Czech River Authority) were measured throughout the study during the
doi:10.1111/j.1439-0426.2008.01164.x fatcat:uemddpb4tbhxtmet7grs5gwrta