DESIGN FOR A PORTABLE, MODULAR STREAM ENCLOSURE EXCLOSURE DEVICE/

We designed a portable, modular enclosure/exclosure device for in situ stream experimentation. The basic enclosure consists of interlocking panels to provide a 1 m(2) area, and combines the easy transportation of small cages with the modular flexibility to construct large enclosu res. In field experiments, we assessed: 1) the potential for mesh size to affect the presence of fish food items; 2) the influence of the en closure mesh on restricting stream water velocity; and 3) the ability of the enclosure to retain fish over short experimental periods. The m esh size (3.2 mm) did not impose a restriction on movement of stream i nvertebrates during a 14 day colonization period. Flow was impeded, bu t not completely restricted by the enclosure mesh. The retention of fi sh within the enclosures was improved through the use of mesh skirting attached to the bottom edges of the enclosure and covered with the na tural stream substrata.