Capture efficiencies of commercial shrimp trawls may improve if their designs took into better account behavioral responses of wild shrimp to approaching cod-end of the trawls. Here we report results of water tunnel-based experimental studies of responses of wild California target prawns to several different near-realistic netting configurations over a range of water velocities (0.3–0.7 m/s). Netting panels were oriented at parallel to water flows (FP) on the bottom of test section, vertical (VT) or diagonal sloping backward (DG), bottom to top. Behavioral responses were recorded by video camera and analyzed frame by frame. Measured responses included rates of penetrating through netting by behavioral features and tail-flip frequencies. Frequencies of prawn passing through the nets increased with flow speed for both orientations and were higher at given speeds for sloped nets. Other behavioral features (e.g., passage head-or tail-first) also varied significantly with water velocities and netting orientation. Interactions of penetrating rates between netting orientations and flow speeds also were significantly dependent, except for prawn size. Additional studies are needed of other shrimp species and at higher water velocities more similar to actual field operations using trawls to improve size selectivity.

Introduction
 Materials and Methods
  Shrimps
  Nettings
  Water tunnel
  Experiments
  Image analyses
  Statistical analysis
 Results
  Behavior at different flow speeds
  Net penetration behavioral parameters
 Discussion
  Model experiments in a water tunnel
  Net penetration parameters
  Mechanisms of net penetration by tail flip
 Acknowledgments
 References

• Yonghae KIM(Institute of Marine Industry, College of Marine Science, Gyeongsang National University) Corresponding author
• Malcolm S. GORDON(Department of Ecology & Evolutionary Biology, University of California)