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 enclosures. In field experiments, we assessed: 1) the potential for mesh size to affect the presence of fish food items; 2) the influence of the enclosure mesh on restricting stream water velocity; and 3) the ability of the enclosure to retain fish over short experimental periods. The mesh size (3.2 mm) did not impose a restriction on movement of stream invertebrates during a 14 day colonization period. Flow was impeded, but not completely restricted by the enclosure mesh. The retention of fish within the enclosures was improved through the use of mesh skirting attached to the bottom edges of the enclosure and covered with the natural stream substrata.