Relating Turbulence and Fish Habitat: A New Approach for Management and Research

Abstract

Understanding how fish perceive turbulence characteristics to utilize complex habitats (large wood, rock, channel bedforms, etc.) is a critical, but poorly understood component of aquatic habitat restoration. Many recent studies attempt to relate turbulence characteristics to habitat utilization, but results are inconsistent for two reasons. First, turbulence is a complex, multi-scale manifestation of fluid flow that can be characterized in different ways with different interpretations. Second, fish behavioral response to flow field features is also complex because both acclimation and learning are important. For example, some studies show that turbulence decreases swimming stability, increases energy expenditure for a given swimming speed, and alters feeding behavior, whereas others show turbulence to decrease energy needed to swim at a given speed and correlates with fish abundance. We describe a Turbulence Attraction and Avoidance (TAA) hypothesis to reconcile inconsistent, even seemingly contradictory, findings. The TAA hypothesis creates a new perspective of turbulence, habitat complexity, and fish habitat occupancy by acknowledging that fish, like all animals, perceive their environment at their own relevant scales and in a conditional manner, dependent on their prior exposure history.

Keywords:

• turbulence
• salmonids
• habitat
• modeling
• perception