Downstream Movement of Leopard Frogs in a Lake Superior Tributary Exemplifies theConcept of a Lotic Macrodrift

摘要

Over two field seasons, 319 downstream-moving leopard frogs (Rana pipiens) werecaptured and retained by a salmonid smolt trap operated in the Bois Brule River of northern Wisconsin. Most leopard frog movement occurred during late summer and autumn but was not conclusively correlated with any environmental factors. This movement was part of a macrodrift that included other larger taxa (e.g. Bufo and Orconectes) not typically retained by the drift nets used by aquatic ecologists to sample aquatic insects. Smolt traps, by virtue of the large volumes of water they strain, can be used to provide hard-to-obtain life history information for a variety of aquatic organisms.