PS 2-23
Does stream-bank vegetation act as fish refugia from high-turbidity water? A field experiment in semi-natural streams
Turbid water caused by natural and anthropogenic disturbances is a major stress factor for stream fishes. Increased turbidity affects them at various levels from physical damage to the gills to predator-prey interactions. Understanding fish refugia from turbid water can provide useful information for increasing the resistance and resilience of their communities. Stream-bank vegetation may provide fish refugia from turbid water because its complex structure prevents a rapid increase in turbidity. To test this possibility, we examined the use of bank vegetation by fishes before, during, and after an artificial turbidity event using large experimental streams in the Aqua Restoration Research Center, central Japan. We established six sets of patches with and without bank vegetation along each of two streams, a treatment stream and a control stream, and added turbid water to the treatment stream.
Results/Conclusions
The fish assemblages in both streams were dominated by water-column species, particularly Zacco platypus, Gnathopogon elongatus, and Carassius auratus complex, and benthic species were rare. When the turbidity event occurred, the total population density of fishes increased significantly only in patches with plants in the treatment stream (up to eight fold). This trend was not observed in patches without plants and in the control stream. These results suggest that bank vegetation acts as fish refugia in high-turbidity events, particularly for water-column fishes. Our study provides evidence for the importance of bank vegetation in conserving riverine fish communities.