來源： Hasegawa and Maekawa 2006; FishBase, 2003
到達日期： 1930 - 1939
Brown trout S. trutta and rainbow trout Oncorhynchus mykiss have been introduced to Hokkaido. Brown trout were first recorded in 1980 and currently inhabit 42 streams (Kudo 2001, in Hasegawa and Maekawa 2006). Rainbow trout were introduced in the 1920s and now inhabit at least 72 streams (Takami and Aoyama 1999, in Hasegawa and Maekawa 2006). Brown and rainbow trout occur sympatrically with native salmonids in several streams (Takami & Aoyama, 1999), which provided an opportunity to examine the effects of introduced salmonids on native salmonid communities.
競爭: Introductions of non-native fishes can lead to the decline or extinction of native species through interspecific interactions (Moyle and Light 1996, in Hasegawa and Maekawa 2006). In particular, many species of salmonids have been introduced into streams throughout the world, primarily for recreational fishing (Fausch 1988, in Hasegawa and Maekawa 2006). Closely related native and introduced salmonids have not coevolved to partition niches, thus interspecific competition can often occur between such species (Krueger and May 1991, in Hasegawa and Maekawa 2006).
Using an artificial stream, habitat use by two sympatric native salmonids in the presence and absence of introduced salmonid species was investigated experimentally. When only native white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou were sympatric, they occupied different microhabitats. In the presence of introduced brown trout S. trutta or rainbow trout Oncorhynchus mykiss, however, white-spotted charr and masu salmon were observed to use a similar habitat and interspecific competition between white-spotted charr and masu salmon was initiated. The study suggested that the coexistence of native salmonids was negatively affected through interspecific competition between native and introduced salmonids.
最後修改 ： 13/07/2006 10:21:49 a.m.