Microhabitat use by Blennius fluviatilis in the Río Matarraña, Spain

SUMMARY.

• 1 Microhabitat use by Blennius fluviatilis in the Río Matarraña, Spain, varied significantly among dates during a 19-month study. Most temporal variation, however, was attributable to changes in microhabitat availability.
• 2 B. fluviatilis demonstrated non-random use of available microhabitats during each sampling period, and generally occupied deeper microhabitats with higher average current velocities dominated by rubblegravel substrates.
• 3 B. fluviatilis also demonstrated non-random use of available nest sites; males generally nested under the largest available pieces of rubble, in areas with less gravel or sand. Water column depth influenced nest site use in two of four study areas.
• 4 We found few microhabitat differences between spawning and nonspawning periods, or between males and females. In addition, microhabitat use was similar among B. fluviatilis size-groups.
• 5 Although B. fluviatilis often were over-represented in deeper, erosional areas, blennies necessarily inhabited a wide range of microhabitats because average current velocities and water depths fluctuated greatly during the study. Tolerance of a broad range of environmental conditions may contribute to the species' persistence in habitats that exhibit extreme seasonal changes in discharge such as the Matarraña.