Selection of Habitat Structure Interstice Size by Bluegills and Largemouth Bass in Ponds

We examined how interstice size in a structure influenced fish use of that structure. We determined preferences of bluegills Lepomis macrochirus (35–95 mm total length, TL) for small (40‐mm), medium (150‐mm), and large (350‐mm) interstices within artificial structure units (2.5 m 3 ) in three 0.16‐hectare ponds both before and after largemouth bass Micropterus salmoides (255–454 mm TL) were added to study ponds. In the absence of predators, yearling bluegills preferred small‐ and medium‐interstice structures over large interstices regardless of major differences in water clarity among ponds. In the presence of largemouth bass, bluegills preferred small interstices over medium and large interstices in all ponds; medium interstices were preferred over large interstices in turbid ponds but not in the clear pond. These preferences were most pronounced in the clear pond where bluegill use of medium‐ and large‐interstice structures was halved after largemouth bass were stocked. The addition of largemouth bass reduced variability in numbers of bluegills using structures in all ponds; although, again, this reduction was most apparent in the clear pond. Largemouth bass preferred medium interstices over small‐ and large‐interstice structures, although predator use of structures was low. Structures made up only 0.9% of the pond area, yet attracted about 5–10% of the bluegills. Structure may have a carrying capacity that limits the number of bluegills using that structure.