| Abstract: | - 1. Most non‐insect invertebrates that occur in streams on tropical Pacific islands are diadromous; they live as juveniles and adults in streams but have larvae that migrate to the ocean to complete their development before returning to fresh water.
- 2. The type of crossing used in the construction of roads to traverse small streams can impede upstream migration and, consequently, colonization of diadromous fauna above the stream crossing.
- 3. A stream in the Opunohu Valley, Moorea, French Polynesia, had the same diadromous fauna of atyid shrimps, palaemonid prawns, and neritid snails occurring above and below an 8 m wide, 10 m long, bottomless culvert (i.e. an open‐bottom bridge) built to flow over natural substrates. However, no diadromous species were found upstream of two 1 m diameter, 8 m long concrete pipes used for a culverted stream crossing. The increased shear stress in the pipe and subsequent downstream erosion of the stream bed probably inhibited upstream migration.
- 4. Modifications to culverted stream crossings, which are widely used on tropical islands, can reduce migration barriers and prevent upstream loss of diadromous stream fauna.
Copyright © 2004 John Wiley & Sons, Ltd. |
